Loss and representativeness in a 43 year follow up of a national birth cohort

Psychological distress from early adulthood to early old age: evidence from the 1946, 1958 and 1970 British birth cohorts

BACKGROUND

Existing evidence on profiles of psychological distress across adulthood uses cross-sectional or longitudinal studies with short observation periods. The objective of this research was to study the profile of psychological distress within the same individuals from early adulthood to early old age across three British birth cohorts.

METHODS

We used data from three British birth cohorts: born in 1946 (n = 3093), 1958 (n = 13 250) and 1970 (n = 12 019). The profile of psychological distress - expressed both as probability of being a clinical case or a count of symptoms based on comparable items within and across cohorts - was modelled using the multilevel regression framework.

RESULTS

In both 1958 and 1970 cohorts, there was an initial drop in the probability of being a case between ages 23-26 and 33-34. Subsequently, the predicted probability of being a case increased from 12.5% at age 36 to 19.5% at age 53 in the 1946 cohort; from 8.0% at age 33 to 13.7% at age 42 in the 1958 cohort and from 15.7% at age 34 to 19.7% at age 42 in the 1970 cohort. In the 1946 cohort, there was a drop in the probability of caseness between ages 60-64 and 69 (19.5% v. 15.2%). Consistent results were obtained with the continuous version of the outcome.

CONCLUSIONS

Across three post-war British birth cohorts midlife appears to be a particularly vulnerable phase for experiencing psychological distress. Understanding the reasons for this will be important for the prevention and management of mental health problems.

Cohort profile: Scotland's record-linkage e-cohorts of people with intellectual disabilities, and autistic people (SCIDA)

PURPOSE

To investigate health, mortality and healthcare inequalities experienced by people with intellectual disabilities, and autistic people, and their determinants; an important step towards identifying and implementing solutions to reduce inequalities. This paper describes the cohorts, record-linkages and variables that will be used.

PARTICIPANTS

Scotland's Census, 2011 was used to identify Scotland's citizens with intellectual disabilities, and autistic citizens, and representative general population samples with neither. Using Scotland's community health index, the Census data (demography, household, employment, long-term conditions) were linked with routinely collected health, death and healthcare data: Scotland's register of deaths, Scottish morbidity data 06 (SMR06: cancer incidence, mortality, treatments), Prescribing Information System (identifying asthma/chronic obstructive pulmonary disease; angina/congestive heart failure/hypertension; peptic ulcer/reflux; constipation; diabetes; thyroid disorder; depression; bipolar disorders; anxiety/sleep; psychosis; attention deficit hyperactivity disorder; epilepsy; glaucoma), SMR01 (general/acute hospital admissions and causes, ambulatory care sensitive admissions), SMR04 (mental health admissions and causes), Scottish Care Information-Diabetes Collaboration (diabetic care quality, diabetic outcomes), national bowel screening programme and cervical screening.

FINDINGS TO DATE

Of the whole population, 0.5% had intellectual disabilities, and 0.6% were autistic. Linkage was successful for >92%. The resultant e-cohorts include: (1) 22 538 people with intellectual disabilities (12 837 men and 9701 women), 4509 of whom are children <16 years, (2) 27 741 autistic people (21 390 men and 6351 women), 15 387 of whom are children <16 years and (3) representative general population samples with neither condition. Very good general health was reported for only 3389 (15.0%) people with intellectual disabilities, 10 510 (38.0%) autistic people, compared with 52.4% general population. Mental health conditions were reported for 4755 (21.1%) people with intellectual disabilities, 3998 (14.4%) autistic people, compared with 4.2% general population.

FUTURE PLANS

Analyses will determine the extent of premature mortality, causes of death, and avoidable deaths, profile of health conditions and cancers, healthcare quality and screening and determinants of mortality and healthcare.

Lost to follow-up in the Norwegian mother, father and child cohort study

BACKGROUND

The aim of pregnancy cohorts was to understand causes and development of health and disease throughout the life course. A major challenge in cohort studies is to avoid selection bias from loss to follow-up.

OBJECTIVE

The aim of this study was to describe what characterises drop out from the Norwegian Mother, Father and Child Cohort Study (MoBa), and provide a resource to inform the interpretation of results from analysis of cohort data.

METHODS

We estimated loss to follow-up in subsets of participants that responded to questionnaire waves in MoBa through an eight-year period and described characteristics of participants who responded to follow-ups. Within each wave of questionnaires, we estimated two exposure-outcome associations: the relationship between maternal smoking during pregnancy and offspring birthweight, and between educational level and pre-pregnancy body mass index (BMI). We explored the use of inverse probability weighting to correct the bias due to loss to follow-up.

RESULTS

Participants who continued to respond were older, higher educated, less likely to smoke and had lower BMI. We observed a decline in participation of current smokers from 22.3% to 17.5%, and participants who reported an unplanned pregnancy dropped from 19.2% to 16.4%. There was a gradual decline in the inverse relationship between maternal smoking during pregnancy and offspring birthweight with increasing follow-up information, indicating that selection bias due to drop out resulted in lower effect estimates. For the relationship between parental educational level and BMI, the inverse association increased with amount of follow-up information, indicating that the selection bias resulted in higher effect estimates. Inverse probability weighting did not completely correct the estimates for bias due to loss to follow-up.

CONCLUSIONS

Participants who remain cohort members are different from subjects who drop out. Users of large cohorts should be aware of selective loss to follow-up and consider imputation or weighting to account for loss to follow-up when analysing questionnaire responses.

From cohort to community: The emotional work of birthday cards in the Medical Research Council National Survey of Health and Development, 1946-2018

The Medical Research Council National Survey of Health and Development (NSHD) is Britain's longest-running birth cohort study. From their birth in 1946 until the present day, its research participants, or study members, have filled out questionnaires and completed cognitive or physical examinations every few years. Among other outcomes, the findings of these studies have framed how we understand health inequalities. Throughout the decades and multiple follow-up studies, each year the study members have received a birthday card from the survey staff. Although the birthday cards were originally produced in 1962 as a method to record changes of address at a time when the adolescent study members were potentially leaving school and home, they have become more than that with time. The cards mark, and have helped create, an ongoing evolving relationship between the NSHD and the surveyed study members, eventually coming to represent a relationship between the study members themselves. This article uses the birthday cards alongside archival material from the NSHD and oral history interviews with survey staff to trace the history of the growing awareness of importance of emotion within British social science research communities over the course of the 20th and early 21st centuries. It documents changing attitudes to science's dependence on research participants, their well-being, and the collaborative nature of scientific research. The article deploys an intertextual approach to reading these texts alongside an attention to emotional communities drawing on the work of Barbara Rosenwein.

Health and study dropout: health aspects differentially predict attrition

Background

Participant dropout poses significant problems in longitudinal survey studies. Although it is often assumed that a participant’s health predicts future study dropout, only a few studies have examined this topic, with conflicting findings. This study aims to contribute to the literature by clarifying the relationship between different aspects of health and study dropout.

Methods

The 2008 baseline sample of the German Aging Survey was used to predict study dropout (N = 4442). Indicators of health included physical health using the number of chronic conditions, physical functioning using the SF-36 Physical Functioning subscale, cognitive functioning using the digit symbol substitution test, and depression using the CESD-15.

Results

It was found that different aspects of health had differential associations with survey dropout: Worse physical functioning and in part worse cognitive functioning predicted increased dropout rates; contrarily, worse physical health predicted decreased dropout when controlling for other health aspects and covariates. Depression was not significantly related to study dropout.

Conclusions

Therefore, participants with chronic conditions, but minimal physical and cognitive disability were most likely to participate in the future. These findings suggest that health has a complex relationship with survey dropout and must be accounted for in longitudinal studies. Neglecting this systematic attrition due to health problems bears the risk of severely under- or overestimating health-related effects and trends.

Childhood growth and development and DNA methylation age in mid-life

BACKGROUND

In the first study of its kind, we examine the association between growth and development in early life and DNAm age biomarkers in mid-life.

METHODS

Participants were from the Medical Research Council National Survey of Health and Development (n = 1376). Four DNAm age acceleration (AgeAccel) biomarkers were measured when participants were aged 53 years: AgeAccelHannum; AgeAccelHorvath; AgeAccelLevine; and AgeAccelGrim. Exposure variables included: relative weight gain (standardised residuals from models of current weight z-score on current height, and previous weight and height z-scores); and linear growth (standardised residuals from models of current height z-score on previous height and weight z-scores) during infancy (0-2 years, weight gain only), early childhood (2-4 years), middle childhood (4-7 years) and late childhood to adolescence (7-15 years); age at menarche; and pubertal stage for men at 14-15 years. The relationship between relative weight gain and linear growth and AgeAccel was investigated using conditional growth models. We replicated analyses from the late childhood to adolescence period and pubertal timing among 240 participants from The National Child and Development Study (NCDS).

RESULTS

A 1SD increase in relative weight gain in late childhood to adolescence was associated with 0.50 years (95% CI 0.20, 0.79) higher AgeAccelGrim. Although the CI includes the null, the estimate was similar in NCDS [0.57 years (95% CI - 0.01, 1.16)] There was no strong evidence that relative weight gain and linear growth in childhood was associated with any other AgeAccel biomarker. There was no relationship between pubertal timing in men and AgeAccel biomarkers. Women who reached menarche ≥ 12 years had 1.20 years (95% CI 0.15, 2.24) higher AgeAccelGrim on average than women who reached menarche < 12 years; however, this was not replicated in NCDS and was not statistically significant after Bonferroni correction.

CONCLUSIONS

Our findings generally do not support an association between growth and AgeAccel biomarkers in mid-life. However, we found rapid weight gain during pubertal development, previously related to higher cardiovascular disease risk, to be associated with older AgeAccelGrim. Given this is an exploratory study, this finding requires replication.

Pubertal mammary gland development is a key determinant of adult mammographic density

Mammographic density refers to the radiological appearance of fibroglandular and adipose tissue on a mammogram of the breast. Women with relatively high mammographic density for their age and body mass index are at significantly higher risk for breast cancer. The association between mammographic density and breast cancer risk is well-established, however the molecular and cellular events that lead to the development of high mammographic density are yet to be elucidated. Puberty is a critical time for breast development, where endocrine and paracrine signalling drive development of the mammary gland epithelium, stroma, and adipose tissue. As the relative abundance of these cell types determines the radiological appearance of the adult breast, puberty should be considered as a key developmental stage in the establishment of mammographic density. Epidemiological studies have pointed to the significance of pubertal adipose tissue deposition, as well as timing of menarche and thelarche, on adult mammographic density and breast cancer risk. Activation of hypothalamic-pituitary axes during puberty combined with genetic and epigenetic molecular determinants, together with stromal fibroblasts, extracellular matrix, and immune signalling factors in the mammary gland, act in concert to drive breast development and the relative abundance of different cell types in the adult breast. Here, we discuss the key cellular and molecular mechanisms through which pubertal mammary gland development may affect adult mammographic density and cancer risk.

Socioeconomic inequalities in blood pressure: co-ordinated analysis of 147,775 participants from repeated birth cohort and cross-sectional datasets, 1989 to 2016

BACKGROUND

High blood pressure (BP) is a key modifiable determinant of cardiovascular disease and a likely determinant of other adverse health outcomes. While socioeconomic inequalities in BP are well documented, it remains unclear (1) how these inequalities have changed across time, given improvements over time in the detection and treatment of high BP (hypertension); (2) whether BP inequalities are present below and above hypertension treatment thresholds; and (3) whether socioeconomic position (SEP) across life has cumulative effects on BP. We sought to address these gaps using evidence from two complementary sources: birth cohort and repeated cross-sectional datasets.

METHODS

We used three British birth cohort studies-born in 1946, 1958, and 1970-with BP measured at 43-46 years (in 1989, 2003, and 2016), and 21 repeated cross-sectional datasets-the Health Survey for England (HSE), with BP measured among adults aged ≥ 25 years (1994-2016). Adult education attainment was used as an indicator of SEP in both datasets; childhood father's social class was used as an alternative indicator of (early life) SEP in cohorts. Adjusting for the expected average effects of antihypertensive medication use, we used linear regression to quantify SEP differences in mean systolic BP (SBP), and quantile regression to investigate whether inequalities differed across SBP distributions-below and above hypertension treatment thresholds.

RESULTS

In both datasets, lower educational attainment was associated with higher SBP, with similar absolute magnitudes of inequality across the studied period. Differences in SBP by education (Slope Index of Inequality) based on HSE data were 3.0 mmHg (95% CI 1.8, 4.2) in 1994 and 4.3 mmHg (2.3, 6.3) in 2016. Findings were similar for diastolic BP (DBP) and survey-defined hypertension. Inequalities were found across the SBP distribution in both datasets-below and above the hypertension threshold-yet were larger at the upper tail; in HSE, median SBP differences were 2.8 mmHg (1.7, 3.9) yet 5.6 mmHg (4.9, 6.4) at the 90th quantile. Adjustment for antihypertensive medication use had little impact on the magnitude of inequalities; in contrast, associations were largely attenuated after adjustment for body mass index. Finally, cohort data suggested that disadvantage in early and adult life had cumulative independent associations with BP: cohort-pooled differences in SBP were 5.0 mmHg (3.8, 6.1) in a score combining early life social class and own education, yet were 3.4 mmHg (2.4, 4.4) for education alone.

CONCLUSION

Socioeconomic inequalities in BP have persisted from 1989 to 2016 in Britain/England, despite improved detection and treatment of high BP. To achieve future reductions in BP inequalities, policies addressing the wider structural determinants of high BP levels are likely required, particularly those curtailing the obesogenic environment-targeting detection and treatment alone is unlikely to be sufficient.

Outcome Assessment in Epidemiological Studies of Low-Dose Radiation Exposure and Cancer Risks: Sources, Level of Ascertainment, and Misclassification

BACKGROUND

Outcome assessment problems and errors that could lead to biased risk estimates in low-dose radiation epidemiological studies of cancer risks have not been systematically evaluated.

METHODS

Incidence or mortality risks for all cancers or all solid cancers combined and for leukemia were examined in 26 studies published in 2006-2017 involving low-dose (mean dose ≤100 mGy) radiation from environmental, medical, or occupational sources. We evaluated the impact of loss to follow-up, under- or overascertainment, outcome misclassification, and changing classifications occurring similarly or differentially across radiation dose levels.

RESULTS

Loss to follow-up was not reported in 62% of studies, but when reported it was generally small. Only one study critically evaluated the completeness of the sources of vital status. Underascertainment of cancers ("false negatives") was a potential shortcoming for cohorts that could not be linked with high-quality population-based registries, particularly during early years of exposure in five studies, in two lacking complete residential history, and in one with substantial emigration. False positives may have occurred as a result of cancer ascertainment from self- or next-of-kin report in three studies or from enhanced medical surveillance of exposed patients that could lead to detection bias (eg, reporting precancer lesions as physician-diagnosed cancer) in one study. Most pediatric but few adult leukemia studies used expert hematopathology review or current classifications. Only a few studies recoded solid cancers to the latest International Classification of Diseases or International Classification of Diseases for Oncology codes. These outcome assessment shortcomings were generally nondifferential in relation to radiation exposure level except possibly in four studies.

CONCLUSION

The majority of studies lacked information to enable comprehensive evaluation of all major sources of outcome assessment errors, although reported data suggested that the outcome assessment limitations generally had little effect on risk or biased estimates towards the null except possibly in four studies.

Adolescent affective symptoms and mortality

BACKGROUND

Little is known about the relationship between adolescent affective problems (anxiety and depression) and mortality.AimsTo examine whether adolescent affective symptoms are associated with premature mortality, and to assess whether this relationship is independent of other developmental factors.

METHOD

Data (n = 3884) was from Britain's oldest birth cohort study - the National Survey of Health and Development. Adolescent affective symptoms were rated by teachers at ages 13 and 15 years: scores were summed and classified into three categories: mild or no, moderate and severe symptoms (1st-50th, 51st-90th and 91st-100th percentiles, respectively). Mortality data were obtained from national registry data up to age 68 years. Potential confounders were parental social class, childhood cognition and illness, and adolescent externalising behaviour.

RESULTS

Over the 53-year follow-up period, 12.2% (n = 472) of study members died. Severe adolescent affective symptoms were associated with an increased rate of mortality compared with those with mild or no symptoms (gender adjusted hazard ratio 1.76, 95% CI 1.33-2.33). This association was only partially attenuated after adjustment for potential confounders (fully adjusted hazard ratio 1.61, 95% CI 1.20-2.15). There was suggestive evidence of an association across multiple causes of death. Moderate symptoms were not associated with mortality.

CONCLUSIONS

Severe adolescent affective symptoms are associated with an increased rate of premature mortality over a 53-year follow-up period, independent of potential confounders. These findings underscore the importance of early mental health interventions.Declaration of interestNone.

Motor performance in early life and participation in leisure-time physical activity up to age 68 years

BACKGROUND

This study examined associations between motor performance in early life and leisure-time physical activity (LTPA) participation across adulthood, and whether these changed with age.

METHODS

Data were from 2526 participants from the Medical Research Council National Survey of Health and Development. Motor indicators were mother-reported ages at first standing and walking, teacher-rated games ability at age 13, and finger- and foot-tapping speed at age 15. LTPA was reported at ages 36, 43, 53, 60-64, and 68 years and classed at each age as none, moderate (1-4/mo), or regular (≥5/mo). Associations were examined using mixed-effects Poisson regression models with robust error variance.

RESULTS

Better ability at games and faster tapping speed were associated with more frequent participation in LTPA across adulthood, for example, fully adjusted relative risk of regular LTPA across adulthood (vs none) for above-average ability (vs below average or average) = 1.46 (95% CI 1.32, 1.61); and per 10-unit higher number of finger-taps/15 seconds = 1.04 (95% CI 1.02, 1.07). These associations did not vary by age (P ≥ .33 for interactions with age at LTPA). Ages at reaching motor milestones were not associated with LTPA (eg, fully adjusted relative risk of regular LTPA across adulthood for walking ≤10 and ≥18 months (vs 11-17 months) were 1.01 (95% CI 0.86, 1.20) and 0.89 (95% CI 0.75, 1.06) respectively.

CONCLUSIONS

Better ability at games and faster tapping speed in adolescence were associated with greater participation in LTPA throughout adult life; from age 36 up to age 68. Childhood motor skill interventions may therefore have the potential to promote lifelong LTPA.

Decline in Search Speed and Verbal Memory Over 26 Years of Midlife in a British Birth Cohort

BACKGROUND

Cognitive capabilities change in later life, although their onset and rate of decline, and how they are shaped by lifetime socioeconomic position, childhood cognition and adult health status are all unclear.

METHODS

From the Medical Research Council National Survey of Health and Development, we analysed 3,192 participants undergoing one or more cognitive assessments at ages 43, 53, 60-64 and 69. Linear mixed models described cognitive trajectories, adjusting for factors across the life course.

RESULTS

For both search speed and verbal memory, better performance at age 43 (the intercept) was associated with higher paternal and own education, childhood cognition, and adult occupational class. For search speed, the trajectory was best described as a quadratic function (decline of 45.6 letters/5-years + 4.6 letters). Verbal memory showed a linear decline of 0.20 words/5-years between ages 43 and 60 and a steeper linear decline of 0.95 words/5-years between ages 60 and 69. Decline in verbal memory in the latter period was steeper in those with higher educational achievements at age 26 (additional 0.28 words/5-years for highest attainment).

CONCLUSIONS

Decline in verbal memory and search speed across midlife is evident, though with different non-linear trajectories. By implication, pathways to cognitive impairment and dementia in older age may have their origins in this period.

Markers of pubertal timing and leisure-time physical activity from ages 36 to 68 years: findings from a British birth cohort

OBJECTIVES

We aimed to examine associations between markers of pubertal timing and leisure-time physical activity (LTPA) from ages 36 to 68 years in men and women from the Medical Research Council National Survey of Health and Development.

STUDY DESIGN

Pubertal timing was ascertained by physicians at age 14-15 years. Boys were grouped, based on their secondary sexual characteristics, as prepubescent, in early-stage puberty, advanced stage puberty or fully mature at age 14-15 years. Girls were grouped as reaching menarche ≤11, 12, 13 or ≥14 years. LTPA was reported at ages 36, 43, 53, 60-64 and 68 years and classified as active or inactive at each age. Associations were examined using standard and mixed-effects logistic regression models.

RESULTS

Of 5362 singleton births recruited, 1499 men and 1409 women had at least one measure of LTPA and data on pubertal timing and selected covariates. When compared with men that were fully mature at age 14-15 years, those that were in advanced stage and early-stage puberty, but not the prepubescent stage, had lower likelihood of LTPA at younger but not older adult ages (p=0.06 for pubertal status-by-age at LTPA interaction in mixed-effects model). For example, fully adjusted ORs of LTPA (vs no LTPA) at ages 36 and 68 years, respectively, for advanced puberty versus fully mature were 0.69 (95% CIs 0.50 to 0.96) and 1.03 (0.72 to 1.47). Age at menarche was not associated with LTPA at any age (p_interaction with age at LTPA=0.9). For example, OR (from mixed-effects model) of LTPA between 36 and 68 years was 1.23 (0.93, 1.63) for menarche at 13 vs ≤11 years.

CONCLUSIONS

In a nationally representative study, there was little evidence to suggest that pubertal timing was an important correlate of LTPA between ages 36 and 68 years. Maturity-related variations in adolescents' LTPA may be transitory and lose importance over time.

Combined Impact of Smoking and Early-Life Exposures on Adult Lung Function Trajectories

RATIONALE

Both adverse early-life exposures and adult smoking can negatively influence adult lung function trajectory, but few studies consider how the impact of early-life exposures may be modified by subsequent smoking.

METHODS

The Medical Research Council National Survey of Health and Development is a nationally representative cohort, initially of 5,362 individuals, followed since enrollment at birth in March 1946. Using data collected prospectively across life and multilevel modeling, we investigated how the relationships between early-life exposures (infant lower respiratory infection, manual social class, home overcrowding, and pollution exposure) and FEV₁ and FVC trajectories between ages 43 and 60-64 years were influenced by smoking behavior.

MEASUREMENTS AND MAIN RESULTS

Among 2,172 individuals, there were synergistic interactions of smoking with infant respiratory infection (P = 0.04) and early-life home overcrowding (P = 0.009), for FEV₁ at 43 years. Within smoker-stratified models, there were FEV₁ deficits among ever-smokers associated with infant lower respiratory infection (-108.2 ml; P = 0.001) and home overcrowding (-89.2 ml; P = 0.002), which were not evident among never-smokers (-15.9 ml; P = 0.69 and -13.7 ml; P = 0.70, respectively). FVC modeling, including 1,960 individuals, yielded similar results. FEV₁ decline was greater in smokers (P < 0.001), but there was no effect of any early-life exposure on FEV₁ decline. Neither smoking nor early-life exposures were associated with FVC decline.

CONCLUSIONS

Besides accelerating adult FEV₁ decline, cigarette smoking also modifies how early-life exposures impact on both midlife FEV₁ and FVC. These findings are consistent with smoking impairing pulmonary development during adolescence or early adulthood, thereby preventing catch-up from earlier acquired deficits.

Socioeconomic Inequalities in Body Mass Index across Adulthood: Coordinated Analyses of Individual Participant Data from Three British Birth Cohort Studies Initiated in 1946, 1958 and 1970

BACKGROUND

High body mass index (BMI) is an important contributor to the global burden of ill-health and health inequality. Lower socioeconomic position (SEP) in both childhood and adulthood is associated with higher adult BMI, but how these associations have changed across time is poorly understood. We used longitudinal data to examine how childhood and adult SEP relates to BMI across adulthood in three national British birth cohorts.

METHODS AND FINDINGS

The sample comprised up to 22,810 participants with 77,115 BMI observations in the 1946 MRC National Survey of Health and Development (ages 20 to 60-64), the 1958 National Child Development Study (ages 23 to 50), and the 1970 British Cohort Study (ages 26 to 42). Harmonized social class-based SEP data (Registrar General's Social Class) was ascertained in childhood (father's class at 10/11 y) and adulthood (42/43 years), and BMI repeatedly across adulthood, spanning 1966 to 2012. Associations between SEP and BMI were examined using linear regression and multilevel models. Lower childhood SEP was associated with higher adult BMI in both genders, and differences were typically larger at older ages and similar in magnitude in each cohort. The strength of association between adult SEP and BMI did not vary with age in any consistent pattern in these cohorts, but were more evident in women than men, and inequalities were larger among women in the 1970 cohort compared with earlier-born cohorts. For example, mean differences in BMI at 42/43 y amongst women in the lowest compared with highest social class were 2.0 kg/m2 (95% CI: -0.1, 4.0) in the 1946 NSHD, 2.3 kg/m2 (1.1, 3.4) in the 1958 NCDS, and 3.9 kg/m2 (2.3, 5.4) the in the 1970 BCS; mean (SD) BMI in the highest and lowest social classes were as follows: 24.9 (0.8) versus 26.8 (0.7) in the 1946 NSHD, 24.2 (0.4) versus 26.5 (0.4) in the 1958 NCDS, and 24.2 (0.3) versus 28.1 (0.8) in the 1970 BCS. Findings did not differ whether using overweight or obesity as an outcome. Limitations of this work include the use of social class as the sole indicator of SEP-while it was available in each cohort in both childhood and adulthood, trends in BMI inequalities may differ according to other dimensions of SEP such as education or income. Although harmonized data were used to aid inferences about birth cohort differences in BMI inequality, differences in other factors may have also contributed to findings-for example, differences in missing data.

CONCLUSIONS

Given these persisting inequalities and their public health implications, new and effective policies to reduce inequalities in adult BMI that tackle inequality with respect to both childhood and adult SEP are urgently required.

The MRC National Survey of Health and Development reaches age 70: maintaining participation at older ages in a birth cohort study

A life course approach to ageing relies on maintaining participation rates in national birth cohorts and other long-term longitudinal studies. This reduces the risk of selective attrition biasing associations between lifetime risk factors and health outcomes in later life and ensures the studies remain as representative as possible of the original population. We report the participation patterns for a postal questionnaire and home visit at 68-69 years of study members in the MRC National Survey of Health and Development, the oldest and longest-running British birth cohort study. We investigated how participation varied by lifetime and recent contact, health status, previous clinical feedback and study engagement, taking account of prior socioeconomic and cognitive characteristics. Overall participation and home visit participation remained high (94 and 80%, respectively) and there were no gender differences. Participation was higher in those with higher levels of prior contact and lower in those with the poorest health status. Having previously received clinical feedback on actionable blood results was associated with reduced home visit participation but other forms of clinical feedback were not associated with subsequent participation. Activities that fostered study engagement were associated with increased home visit participation. These findings inform strategies to maintain participation in life course studies.

Verbal memory and search speed in early midlife are associated with mortality over 25 years' follow-up, independently of health status and early life factors: a British birth cohort study

BACKGROUND

Cognitive capabilities in childhood and in late life are inversely associated with mortality rates. However, it is unclear if adult cognition, at a time still relatively free from comorbidity, is associated with subsequent mortality, and whether this explains the associations of early life factors with adult mortality.

METHODS

We used data from the MRC National Survey of Health and Development, a birth cohort study prospectively assessing 5362 participants born in 1946. The present analysis includes participants followed up from age 43 and undergoing cognitive assessment (verbal memory and search speed). Mortality outcomes were notified through linkage with a national register. Cox regression was used to estimate mortality hazards in relation to cognitive performance at age 43, adjusting for early life factors, socioeconomic position and health status.

RESULTS

Data were available on 3192 individuals. Univariable analyses indicated that adult verbal memory and search speed, parental factors, childhood cognition and educational attainment were associated with mortality. However, multivariable models showed that the mortality associations with earlier life factors were explained by adult cognitive capability. A standard deviation increase in verbal memory and search speed scores was associated with lower mortality rates [hazard ratio (HR) = 0.86, 95% confidence interval (CI) 0.77-0.97, P = 0.02; HR = 0.88, 95% CI 0.78-1.00, P = 0.05, respectively), after adjustment for adult health.

CONCLUSIONS

Cognitive capability in early midlife was inversely associated with mortality rates over 25 years and accounted for the associations of family background, childhood cognitive ability and educational attainment with mortality. These findings, in a nationally representative cohort with long-term follow-up, suggest that building cognitive reserve may improve later life health and survival chances.

Associations of Midlife to Late Life Fatigue With Physical Performance and Strength in Early Old Age: Results From a British Prospective Cohort Study

OBJECTIVES

To examine associations of fatigue in midlife and later life with physical performance and strength in early old age.

METHODS

Data on approximately 1800 men and women from the UK Medical Research Council National Survey of Health and Development with data on fatigue at ages 43 and 60 to 64 years were used. Fatigue was defined as perceived tiredness and was assessed prospectively at ages 43 and 60 to 64 years. At both ages, participants were categorized as having no, occasional, or frequent fatigue. Physical performance and strength were measured at age 60 to 64 years using four objective measures: grip strength, standing balance, chair rising, and timed get-up-and-go (TUG) tests.

RESULTS

There were associations between reports of frequent fatigue at both ages and poorer grip strength, chair rise, and TUG performance at 60 to 64 years. Furthermore, individuals reporting frequent fatigue at both ages had weaker grip strength (β = -4.09 kg, 95% confidence interval [CI] = -6.71 to -1.48) and slower chair rise (β = -4.65 repetitions/min, 95% CI = -6.65 to -2.64) and TUG (β = -4.22 cm/s, 95% CI = -12.16 to -2.28) speeds when compared with those who reported no fatigue at both time points. These associations were robust and were maintained after adjustment for a range of covariates including physical activity and health status.

CONCLUSIONS

Reports of frequent fatigue were associated with poorer physical performance in early old age, especially if sustained from midlife to later life. These findings indicate that it is not just fatigue but fatigue sustained across adulthood that has implications for later life functioning.

Life-course body mass index trajectories and blood pressure in mid life in two British birth cohorts: stronger associations in the later-born generation

Background: Little is known about the impact of recent increases in obesity and more rapid gains in body mass index (BMI) on cardiovascular risk factors. We investigated life-course BMI trajectories associations with adult blood pressure (BP) across two generations.

Methods: We used the the 1946 and 1958 British birth cohorts. Joint multivariate response models were fitted to longitudinal BMI measures [7, 11, 16, 20, 26, 36, 43 and 50 y (years): 1946 cohort, n = 4787; 7, 11, 16, 23, 33 and 45 y: 1958 cohort, n = 16 820] and mid-adult BP. We adopted linear spline models with random coefficients to characterize childhood and adult BMI slopes.

Results: Mean systolic BP (SBP) decreased from the earlier- to later-born cohort by 2.8 mmHg in females, not males; mean diastolic BP (DBP) decreased by 3.2-3.3 mmHg (both sexes). Adult BMI was higher in the later- than the earlier-born cohort by 1.3-1.8 kg/m², slopes of BMI trajectory were steeper from early adulthood and associations with adult BP were stronger. Associations between adult BMI and SBP were stronger in the later-born cohort. For males, childhood BMI slope was associated with SBP only in the later-born cohort; the association for adult BMI slope was stronger in the later-born cohort: correlation coefficient r = 0.28 [95% confidence interval (CI): 0.25,0.33] versus 0.13 (0.06,0.20). For females, childhood slope was associated with SBP in both cohorts; adult slope was associated with SBP only in the 1958 cohort [r = 0.34 (0.31,0.37)]. Patterns of child-to-adult BMI associations were similar in relation to DBP.

Conclusions: BP did not increase between two generations born 12 y apart despite higher BMI levels. A stronger association between BMI trajectory and BP in the later-born cohort suggests that BMI-related effects may have been offset by improvements in other factors linked to BP, such as diet and smoking.

Diurnal eating rhythms: association with long-term development of diabetes in the 1946 British birth cohort

BACKGROUND AND AIMS

Few studies have described the association between time-of-day of macronutrient intake and diabetes. This study examined the prospective association between time-of-day and nutrient composition of eating occasions in relation to diabetes incidence in the 1946 British birth cohort.

METHODS AND RESULTS

The study included 1618 survey members who completed dietary assessment at age 43 (1989) and for whom data on glycosylated haemoglobin at age 53 years (1999) were available. Diet was assessed using 5d estimated diaries, divided into seven meal slots: breakfast, mid-morning, lunch, mid-afternoon, dinner, late evening and extras. Diabetes was defined by glycosylated haemoglobin (HbA1c) ≥ 6.5% or diabetes medication use. The association between time-of-day of macronutrient intake at age 43 years and diabetes at age 53 years was assessed using logistic multivariate nutrient density models after adjustment for potential confounders. There were 66 cases of diabetes at age 53 years. Survey members with diabetes obtained 50.4% of their energy from carbohydrate at breakfast compared to 55.9% in survey members without diabetes (P = 0.001). Increasing carbohydrate intake at breakfast at the expense of fat was related to lower odds ratio (OR) of diabetes (OR = 0.86; 95%CI = 0.79-0.93; P < 0.001). This relationship was attenuated after adjustment for body mass index and waist circumference.

CONCLUSION

Increasing energy intake from carbohydrate at the expense of fat at breakfast is inversely associated with 10-year diabetes incidence. However, further studies are required to elucidate whether the type or source of carbohydrates or fat influences the above association.

Using a birth cohort to study ageing: representativeness and response rates in the National Survey of Health and Development

Britain's oldest birth cohort study, the MRC National Survey of Health and Development (NSHD) provides data to explore life time influences on ageing. The latest data collection was undertaken between 2006 and 2011 when study members were aged 60-64 and consisted of postal and pre-assessment questionnaires to eligible study members, followed by invitation to attend one of six clinical research facilities (CRFs) across the UK for clinical assessments, and dietary diaries and activity monitors in the days following the CRF visit. The option of a home visit for clinical assessments was provided if the study member refused or was unable to attend the CRF. We examined response and attrition, here describing rates overall and for postal and clinical assessment modes of data collection, identifying socioeconomic and health-related predictors of response, and assessing the continued representativeness of the sample. In total, 2,661 (84 % of the target sample) responded. Lower educational attainment, lower childhood cognition and lifelong smoking independently predicted lower likelihood of both overall response and CRF cooperation. At 53 years, not owning one's home and not being married predicted lower likelihood of overall response whereas manual social class and obesity predicted lower likelihood of CRF cooperation. Providing for collection of biomedical data in the home and use of assessment instruments and modes to retain study members with lower education attainment, lower cognition and poorer health behaviours should be priorities for helping reduce attrition amongst vulnerable ageing study members.

Time-of-day and nutrient composition of eating occasions: prospective association with the metabolic syndrome in the 1946 British birth cohort

Background:

Diet is a key modifiable factor in the prevention and treatment of the metabolic syndrome. However, few studies have examined the prospective association between time-of-day of nutrient intake and the metabolic syndrome.

Objective:

To examine the association between time-of-day and nutrient composition of eating occasions and the long-term development of metabolic syndrome in the Medical Research Council (MRC) National Survey of Health and Development (NSHD; 1946 British birth cohort).

Methods:

The analysis comprised 1488 survey members who completed at least 3 days of estimated diet records at age 43 years (1989) and for whom data on metabolic syndrome at age 53 years (1999) were available. Dietary records were divided into seven meal slots: breakfast, mid-morning, lunch, mid-afternoon, dinner, late evening and extras. Metabolic syndrome was defined by the criteria of the adult treatment panel (ATPIII8), and was modified to include glycosylated haemoglobin instead of fasting glucose. Associations between time-of-day of nutrient intake at age 43 years and prevalence of metabolic syndrome at age 53 years were assessed using multivariate nutrient density logistic models after adjustment for sex, social class, smoking status, region, alcohol intake and recreational physical activity.

Results:

There were 390 cases of metabolic syndrome at age 53 years. Substituting 5% of energy from carbohydrate for a similar amount of energy from fat at breakfast (odds ratio=0.93; 95% confidence interval=0.89–0.98; P=0.002) and mid-morning at age 43 years (odds ratio=0.96; 95% confidence interval=0.93–0.99; P=0.011) was associated with lower odds of the metabolic syndrome at age 53 years. Carbohydrate intake at breakfast or mid-morning was particularly protective against abdominal obesity (P⩽0.001). Increasing carbohydrate intake at breakfast while simultaneously decreasing fat intake was also negatively related to triacylglycerols (P⩽0.001).

Conclusions:

Increasing carbohydrate intake in the morning while simultaneously reducing fat intake could be protective against long-term development of the metabolic syndrome and its components.

Population heterogeneity in trajectories of midlife blood pressure

BACKGROUND

We investigated whether there are subgroups with different underlying (latent) trajectories of midlife systolic blood pressure (BP), diastolic BP, and pulse pressure in a UK cohort.

METHODS

Data are from 1840 men and 1819 women with BP measured at ages 36, 43, and 53 years. We used unconditional growth mixture models to test for the presence of latent trajectory classes. Extracted classes were described in terms of a number of known lifetime risk factors, and linked to the risk of undiagnosed angina (Rose questionnaire) at age 53 years.

RESULTS

In both sexes for systolic BP, diastolic BP, and pulse pressure, there was a large "normative" class (>90% of the sample) characterized by gentle annual increases (eg, an increase in male systolic BP of 0.9 mm Hg/year [95% confidence interval = 0.9 to 1.0]), with a smaller class for whom the rate of increase was high (eg, an increase in male systolic BP of 3.1 mm Hg/year [2.8 to 3.4]). In women, there was an additional class for whom BP was high at age 36 and remained high. Persons in the "normative" classes were, on average, heavier at birth and taller at age 7 years, had a lower midlife body mass index, and were less likely to be on antihypertensive medication compared with those in other classes. Among those with no diagnosed cardiovascular disease, those in the classes with more strongly increasing systolic BP and pulse pressure were at greatest risk of angina.

CONCLUSION

Our study suggests that in midlife the majority of the population have a gentle underlying increase in BP, but that there also exists an important subgroup in whom BP increases much more markedly. These classes may be useful for identifying those most at risk for cardiovascular disease.

Prevalence and childhood antecedents of depersonalization syndrome in a UK birth cohort

PURPOSE

Depersonalization syndrome is characterised by a sense of unreality about the self [depersonalization (DP)] and/or the outside world [derealization (DR)]. Prevalence estimates vary widely. Little is known about childhood antecedents of the disorder although emotional abuse is thought to play a role.

METHODS

Longitudinal data from 3,275 participants of a UK population-based birth cohort (the MRC National Survey of Health and Development) were used to: (1) assess the prevalence of DP syndrome at age 36, measured by the Present State Examination (PSE); and (2) examine the effects of a range of socio-demographic, childhood adversity and emotional responses as potential risk factors for DP.

RESULTS

Thirty three survey members were classified with DP, yielding a prevalence of 0.95% [95% confidence intervals (CI) 0.56-1.34]. There were no associations with socio-economic status, parental death or divorce; self-reported accidents, childhood depression, tendency to daydream or reactions to criticism. However, teacher-estimated childhood anxiety was a strong independent predictor of adult depersonalization, and there were strong cross-sectional relationships between DP and anxiety and depression caseness.

CONCLUSIONS

To our knowledge this is the first study assessing nationwide prevalence of the DP syndrome and uses longitudinal data to explore childhood risk factors for adult DP. The prevalence of adult DP was slightly lower than reported by other surveys. The study found that childhood anxiety was the only significant predictor of the adult DP syndrome, supporting the view that depersonalisation disorder forms part of the spectrum of responses to anxiety.

Challenges in examining area effects across the life course on physical capability in mid-life: findings from the 1946 British Birth Cohort

A major limitation of past work linking area socioeconomic conditions to health in mid-life has been the reliance on single point in time measurement of area. Using the MRC National Survey of Health and Development, this study for the first time linked place of residence at three major life periods of childhood (1950), young adulthood (1972), and mid-life (1999) to area-socioeconomic data from the nearest census years. Using objective measures of physical capability as the outcome, the purpose of this study was to highlight four methodological challenges of attrition bias, secular changes in socio-economic measures, historical data availability, and changing reporting units over time. In general, standing balance and chair rise time showed clear cross-sectional associations with residing in areas with high deprivation. However, it was the process of overcoming the methodological challenges, which led to the conclusion that in this example percent low social class occupations was the most appropriate measure to use when extending cross-sectional analysis of standing balance and chair rise to life course investigation.

Gender and life course occupational social class differences in trajectories of functional limitations in midlife: findings from the 1946 British birth cohort

BACKGROUND

Older women and those of lower socioeconomic position (SEP) consistently constitute a larger portion of the disabled population than older men or those of higher SEP, yet no studies have examined when in the life course these differences emerge.

METHODS

Prevalence of self-reported limitations in the upper body (gripping or reaching) and lower body (walking or stair climbing) at 43 and 53 years were utilized from 1,530 men and 1,518 women from the British 1946 birth cohort. Generalized linear models with a binomial distribution were used to examine the effects of gender, childhood and adult SEP, and the differences in the SEP effects by gender on the prevalence of limitations at age 43 years and changes in prevalence from 43 to 53 years.

RESULTS

For both genders, the prevalence of upper and lower body limitations were reported at 3%-5% at age 43 years. However, by age 53 years, women's upper body limitations had increased to 28% and lower body limitations to 21%, whereas men's limitations had only increased to 12% and 11%, respectively. Men and women whose father's occupation was manual or whose adult head of household occupation was manual had higher prevalence of both limitations compared with those with non-manual backgrounds. These differences widened with age, especially in women. The effect of adult SEP on the prevalence of limitations was stronger than that of childhood SEP and was partly mediated by educational attainment.

CONCLUSION

Our findings provide the first evidence that prevention of disability in old age should begin early in midlife, especially for women from manual occupation households.

Dairy intake, blood pressure and incident hypertension in a general British population: the 1946 birth cohort

PURPOSE

We aimed to examine the association between intake of different subgroups of dairy products and blood pressure and incident hypertension 10 years later, adjusting for confounding factors.

METHODS

We studied 1,750 British men and women from the 1946 British birth cohort from 1989 to 1999 (age 43 and 53 years, respectively). Diet was assessed by 5-day food diaries using photographs in the estimation of portion size. Systolic (sbp) and diastolic (dbp) blood pressure and prevalent hypertension were assessed at age 43 and 53 years. Linear regression and logistic regression were used to examine 10-year blood pressure levels and incident hypertension by baseline dairy intake.

RESULTS

There was a weak non-significant trend of a protective effect of total dairy intake on blood pressure and incident hypertension, but no evidence for a dose-response relationship (OR for incident hypertension: 0.88 (95% CI 0.68;1.14) 2nd vs. 1st tertile and 0.93 (95% CI 0.72;1.18) 3rd vs. 1st tertile). Higher intake of low-fat and fermented dairy was linked to a higher sbp but in a nonlinear manner. Adjustment for other dietary factors, health behaviours and BMI attenuated these associations.

CONCLUSIONS

Total dairy intake and specific dairy subgroups were not associated with blood pressure and incident hypertension among a representative sample of British adults after adjustment for confounding factors.

Injuries, falls and accidents among adults with intellectual disabilities. Prospective cohort study

BACKGROUND

Injuries are among the leading causes of death and disability in the world and a major public health concern. Falls are a common cause. Young persons with intellectual disabilities (ID) have a higher rate and different pattern of injuries than the general population, but little is known regarding adults.

METHODS

The aim of this study was to determine the incidence and types of injuries experienced by a community-based cohort of adults with ID (n = 511) in a 12-month period. Face-to-face interviews were conducted with participants 2 years after they had first been recruited into a longitudinal study.

RESULTS

Incidence of at least one injury in a 12-month period was 20.5% (105), of which 12.1% (62) was because of falls. Incident injury was predicted by having epilepsy and not having autism. Incident fall injury was predicted by urinary incontinence, while Down syndrome reduced risk.

CONCLUSIONS

Adults with ID do experience a higher rate of injuries and falls when compared with the general population. The results of this study highlight this, and hence the need to work towards the development of interventions for injury and falls prevention in this population.

Dealing with emigration in cohort studies: follow-up of mortality and cancer incidence among Norwegians born between 1967 and 1976

Emigration causes loss to follow-up. The study aim was to assess the influence of the choice of handling migration in population-based cohort studies on estimated mortality and cancer incidence in the population of origin. All persons born in Norway between 1967 and 1976 and who were not registered dead before 1992 (N = 614,176) were followed up in national registries regarding migration movements, death, and incident cancer between 1992 and 2004. A total of 40,366 (6.6%) of the study population had between 1 and 13 migration movements and 5,354 deaths and 4,447 first cancer cases were recorded during follow-up. Four different follow-up scenarios concerning migration were analysed: considering only person-time before emigration; considering person-time as national residents both before emigration and after repatriation; disregarding whether emigration took place or not; and excluding all who emigrated during follow-up. Mortality and cancer incidence rates were compared in Poisson regression models. Mortality and cancer incidence were only marginally influenced by choice of follow-up scenario. Mortality was higher after repatriation, in particular during the first year of follow-up (rate ratio 2.03; 95% confidence interval 1.02-4.03). This excess had little influence on total population rates. Cancer incidence was not affected by repatriation status. Mortality rates after repatriation were probably elevated because persons who expected to die shortly were more prone to return to their native country ("salmon bias"). The analytical choice concerning follow-up has little influence on outcome occurrences in populations with rather low migration rates. However, the best solution is apparently to censor out persons at the date of emigration in order to avoid salmon bias.

Epidemiology of mental ill health in adults with intellectual disabilities

PURPOSE OF REVIEW

Adults with intellectual disabilities experience higher rates of mental ill health than the general population. Despite this, the epidemiological knowledge base remains limited. The purpose of this article is to review mental health epidemiological studies relevant to adults with intellectual disabilities, published since January 2008.

RECENT FINDINGS

Several studies have aimed to build the epidemiological evidence base, particularly with regards to problem behaviours, which appear to be remitting-relapsing conditions rather than necessarily being chronic. Most of such work confirms prevalence and incidence rates, and conducts exploratory analyses to determine factors independently related to mental ill health. Down syndrome protects against problem behaviours and mental ill health (except dementia that occurs at a higher rate), whereas epilepsy does not appear to affect risk for mental ill health. Dementia is four times more common in older persons with intellectual disabilities without Down syndrome than in the general population. Persons with borderline intellectual disabilities also experience higher rates of mental ill health than the general population, but receive fewer treatments.

SUMMARY

This work builds usefully upon previous studies. Further hypothesis-based analyses are needed.

The role of birth cohorts in studies of adult health: the New York women's birth cohort

Epidemiological studies investigating associations between early life factors and adult health are often limited to studying exposures that can be reliably recalled in adulthood or obtained from existing medical records. There are few US studies with detailed data on the pre- and postnatal environment whose study populations are now in adulthood; one exception is the Collaborative Perinatal Project (CPP). We contacted former female participants of the New York site of the CPP who were born from 1959 to 1963 and were prospectively followed for 7 years to examine whether the pre- and postnatal environment is associated with adult health in women 40 years after birth. The New York CPP cohort is particularly diverse; at enrolment, the race/ethnicity distribution of mothers was approximately 30% White, 40% Black and 30% Puerto Rican. Of the 841 eligible women, we successfully traced 375 women (45%) and enrolled 262 women (70% of those traced). Baseline data were available for all eligible women, and we compared those who participated with the remaining cohort (n = 579). Higher family socio-economic status at age 7, availability of maternal social security number, and White race/ethnicity were statistically significantly associated with a higher probability of tracing. Of those traced, race/ethnicity was associated with participation, with Blacks and Puerto Ricans less likely to participate than Whites (OR = 0.5, 95% CI 0.3, 0.8, and OR = 0.5, 95% CI 0.3, 1.0, respectively). In addition, higher weight at 7 years was associated with lower participation (OR = 0.95, 95% CI 0.92, 0.99), but this association was observed only among the non-White participants. None of the other maternal characteristics, infant or early childhood growth measures was associated with participation or with tracing, either overall or within each racial/ethnic subgroup. Daughters' recall of early life factors such as pre-eclampsia (sensitivity = 24%) and birthweight were generally poor, with the latter varying by category of birthweight with the highest sensitivity for the largest babies (81%) and the lowest sensitivity for the smallest babies (54%). These data reinforce the need to rejuvenate existing birth cohorts with prospective data for life course studies of adult health. Understanding the factors that are associated with tracing and participation in these existing cohorts will help in interpreting the validity and generalisability of the findings from these invaluable cohorts.

Adults with intellectual disabilities: prevalence, incidence and remission of self-injurious behaviour, and related factors

BACKGROUND

Self-injurious behaviour (SIB) is a serious condition, with implications for the person, their family and financial costs to the state providing care. The previously reported prevalence of SIB has ranged from 1.7% to 41%, or 1.7%-23.7% in community studies. There has been little study of remission rate, and incidence has not previously been reported. SIB has been reported to be individually associated with lower ability, autism and communication impairments, but given the inter-relationships between these three factors, it is not known whether they are independently associated with SIB. This study investigates the point prevalence, incidence and remission rates of SIB among the adult population with intellectual disabilities (ID), and explores which factors are independently associated with SIB.

METHOD

A prospective cohort study design was used in a general community setting. The participants were all adults (16 years and over) with ID in a defined geographical area. Individual assessments were conducted with all participants.

RESULTS

The point prevalence of SIB (as defined by DC-LD) was 4.9%, the two-year incidence was 0.6%, and two-year remission rate was 38.2%. Independently related to SIB were: lower ability level, not living with a family carer, having attention deficit hyperactivity disorder, visual impairment, and not having Down syndrome. Other factors, including communication impairment, autism, and level of deprivation of the area resided within, were not related.

CONCLUSIONS

SIB is not as enduring and persistent as previously thought; a significant proportion gains remission in this time period. This should provide hope for families, paid carers and professionals, and reduce therapeutic nihilism. Our study is a first tentative step towards identifying risk-markers for SIB, and developing aetiological hypotheses for subsequent testing. The extent to which SIB may be a relapsing-remitting (episodic) condition requires further investigation, so does further hypothesis-based investigation of factors that might be predictive of incidence of, and remission from, SIB.

Adults with intellectual disabilities: prevalence, incidence and remission of aggressive behaviour and related factors

INTRODUCTION

Aggressive behaviours can be disabling for adults with intellectual disabilities (ID), with negative consequences for the adult, their family and paid carers. It is surprising how little research has been conducted into the epidemiology of these needs, given the impact they can have. This study investigates point prevalence, 2-year incidence and 2-year remission rates for aggressive behaviour (physically aggressive, destructive and verbally aggressive), and it investigates which factors are independently associated with aggressive behaviour.

METHODS

All adults with ID - within a geographically defined area of Scotland, UK - were recruited to a longitudinal cohort. At baseline, assessments were undertaken of demography, lifestyle, supports, development, problem behaviours, disabilities and physical and mental health. These were repeated for a 2-year period.

RESULTS

At baseline, the participation rate was 1023 (65.5%). After 2 years, the cohort retention was 651 adults. The point prevalence of Diagnostic Criteria for Psychiatric Disorders for Use with Adults with Learning Disabilities/Mental Retardation (DC-LD) aggressive behaviour was 9.8% (95% confidence interval = 8.0-11.8%), 2-year incidence was 1.8%, and 2-year remission rate from all types of aggressive behaviour meeting DC-LD criteria was 27.7%. The factors independently associated with aggressive behaviours were lower ability, female gender, not living with a family carer, not having Down syndrome, having attention-deficit hyperactivity disorder and having urinary incontinence. Incidence of aggressive behaviour meeting DC-LD criteria in adult life is similar to that for each of psychotic, anxiety and organic disorders.

CONCLUSIONS

Aggressive behaviour is common among adults with ID, but contrary to previous suggestions, more than a quarter remit within the short to medium term. This is important knowledge for professionals as well as the person and her/his family and paid carers. There is much yet to learn about the mechanisms underpinning aetiology and maintenance of aggressive behaviour in this population, and exploratory epidemiological investigations such as this have a role to play in progressing research towards further hypothesis testing and trials to influence clinical practice, service development and policy.

Paths to literacy and numeracy problems: evidence from two British birth cohorts

BACKGROUND

To test a life course model linking circumstances of origin to self-reported literacy and numeracy problems in midlife, and to investigate the effects in this model of changing social circumstances in two post-war cohorts.

METHODS

Based on data from men and women in the British 1946 and 1958 birth cohorts, we used the relative index of inequality and logistical regression to test associations between father's occupation, childhood cognition, educational attainment, own occupation in the third decade, and a binary variable representing self-reported literacy and numeracy problems in the fourth decade.

RESULTS

There was a lower frequency of literacy and numeracy problems in the 1958 cohort than in the 1946 cohort. In both cohorts there were associations between father's occupation and childhood cognition, educational attainment and own occupation, a pattern that was mirrored by the associations between childhood cognition, educational attainment and own occupation to adult literacy and numeracy problems. Positive associations between childhood cognition and educational attainment, and between educational attainment and own occupation, were stronger in the 1946 cohort than in the 1958 cohort. However, inverse associations between educational attainment and literacy and numeracy problems were stronger in the 1958 cohort, possibly reflecting the expansion of secondary education in the intervening years.

CONCLUSIONS

Literacy and numeracy problems have a robust structure of life course associations, although the changing pattern of these associations may reflect important social structural changes from the early post-war years to the early 1960s in the UK.

Socioeconomic position and hysterectomy: a cross-cohort comparison of women in Australia and Great Britain

OBJECTIVES

To examine the associations between indicators of socioeconomic position (SEP) and hysterectomy in two Australian and two British cohorts.

STUDY POPULATION

Women participating in the Australian Longitudinal Study on Women's Health (ALSWH), born 1921-1926 and 1946-1951, and two cohorts of British women, the British Women's Heart and Health Study and the MRC National Survey of Health and Development, born at similar times (1920 to 1939 and 1946, respectively) and surveyed at similar ages to the ALSWH cohorts.

METHODS

Relative indices of inequality were derived for own and head of household occupational class, educational level attained and age at leaving school. Logistic regression was used to test the associations between these indicators of SEP and self-reported hysterectomy and/or oophorectomy.

RESULTS

Inverse associations between indicators of SEP and hysterectomy were found in both the Australian and British cohorts of women born in 1946 or later. There was also evidence of an inverse association between education and hysterectomy in the older Australian cohort. However, the associations in this older cohort were weaker than those found in the mid-aged Australian cohort. In the older British cohort, born in the 1920s and 1930s, little evidence of association between SEP in adulthood and hysterectomy was found.

CONCLUSIONS

These results suggest that inverse associations between indicators of SEP and hysterectomy are stronger in younger than in older cohorts in both Australia and Great Britain. They provide further evidence of the dynamic nature of the association between indicators of SEP and hysterectomy.

Meat consumption after disaggregation of meat dishes in a cohort of British adults in 1989 and 1999 in relation to diet quality

BACKGROUND/OBJECTIVES

The aim of the study was to quantify more precisely the meat intake of a cohort of adults in the UK by disaggregating composite meat dishes.

SUBJECTS/METHODS

Subjects were members of the Medical Research Council National Survey of Health and Development, 1946 birth cohort. Five-day diaries were collected from 2256 men and women in 1989 and 1772 men and women in 1999. From the details provided, composite meat dishes were broken down into their constituent parts and the meat fraction was added to meat portions only. Meat intake was classified as red meat, processed meat and poultry.

RESULTS

Meat consumption without disaggregation of meat dishes resulted in a mean overestimation of 50% in men and 33% in women. Red meat consumption fell between 1989 and 1999 from 51.7 to 41.5 g per day in men and 35.7 to 30.1 g per day in women. Poultry consumption rose from 21.6 to 32.2 g per day in men and 18.2 to 29.4 g per day in women. Re-calculating red meat intakes resulted in the percentage of subjects in 1999 consuming more than the recommendation of the World Cancer Research Fund falling from 30 to 12%. Increasing consumption of red and processed meat was associated with increased intakes of energy, fat, haem iron, zinc and vitamin B(12), and lower intake of fibre. Increased sodium intake was associated with increased consumption of processed meat.

CONCLUSIONS

Disaggregation of meat dishes provided a more precise estimate of meat consumption. The quantity of red or processed meat in the diet was reflected in the nutrient content of the entire diet.

Consumption of red or processed meat does not predict risk factors for coronary heart disease; results from a cohort of British adults in 1989 and 1999

OBJECTIVES

To investigate whether a high consumption of red or processed meat is associated with increased risk of coronary heart disease (CHD).

SUBJECTS/METHODS

The subjects were 517 men and 635 women, who were members of the Medical Research Council National Survey of Health and Development, 1946 birth cohort. Assessment of diet was carried out at two time points 1989 and 1999 with outcome measures collected in 1999. Food intake data were recorded in 5-day diaries. Meat consumption was estimated by adding individual meat portions to the meat fractions of composite dishes.

RESULTS

There was no significant association between red or processed meat consumption in 1989 and 1999 and serum cholesterol concentrations and blood pressure measured in 1999. The combined intake of red and processed meat in 1999 had a significant positive association with blood pressure in men only. Red and processed meat intakes in 1989, separately and combined, had a significant positive association with waist circumference in 1999: a 10 g increase in red meat consumption accounted for a 0.3 cm increase in waist circumference; P=0.04 (men), 0.05 (women).

CONCLUSIONS

Consumption of red or processed meat assessed separately was not related to the major risk factors for CHD but contributed to increased waist circumference that has also been identified as a risk factor.

Incidence and predictors of mental ill-health in adults with intellectual disabilities: prospective study

BACKGROUND

The point prevalence of mental ill-health among adults with intellectual disabilities is 40.9%, but its incidence is unknown.

AIMS

To determine the incidence and possible predictors of mental ill-health.

METHOD

Prospective cohort study to measure mental ill-health in adults with mild to profound intellectual disabilities.

RESULTS

Cohort retention was 70% (n=651). The 2-year incidence of mental ill-health was 16.3% (12.6% excluding problem behaviours, and 4.6% for problem behaviours) and the standardised incidence ratio was 1.87 (95% CI1.51-2.28). Factors related to incident mental ill-health have some similarities with those in the general population, but also important differences. Type of accommodation and support, previous mental ill-health, urinary incontinence, not having impaired mobility, more severe intellectual disabilities, adult abuse, parental divorce in childhood and preceding life events predicted incident ill-health; however, deprivation, other childhood abuse or adversity, daytime occupation, and marital and smoking status did not.

CONCLUSIONS

This is a first step towards intervention trials, and identifying subpopulations for more proactive measures. Public health strategy and policy that is appropriate for this population should be developed.

Examining life-course influences on chronic disease: the importance of birth cohort studies from low- and middle- income countries. An overview

The objectives of this overview are to describe the past and potential contributions of birth cohorts to understanding chronic disease aetiology; advance a justification for the maintenance of birth cohorts from low- and middle-income countries (LMIC); provide an audit of birth cohorts from LMIC; and, finally, offer possible future directions for this sphere of research. While the contribution of birth cohorts from affluent societies to understanding disease aetiology has been considerable, we describe several reasons to anticipate why the results from such studies might not be directly applied to LMIC. More than any other developing country, Brazil has a tradition of establishing, maintaining and exploiting birth cohort studies. The clear need for a broader geographical representation may be precipitated by a greater collaboration worldwide in the sharing of ideas, fieldwork experience, and cross-country cohort data comparisons in order to carry out the best science in the most efficient manner. This requires the involvement of a central overseeing body--such as the World Health Organization--that has the respect of all countries and the capacity to develop strategic plans for 'global' life-course epidemiology while addressing such issues as data-sharing. For rapid progress to be made, however, there must be minimal bureaucratic entanglements.

Psychosis and adults with intellectual disabilities. Prevalence, incidence, and related factors

OBJECTIVE

To determine the point prevalence, incidence, and remission over a 2-year period of psychosis in adults with intellectual disabilities, and to investigate demographic and clinical factors hypothesised to be associated with psychosis.

METHOD

A population-based cohort of adults with intellectual disabilities (n = 1,023) was longitudinally studied. Comprehensive face-to-face mental health assessments to detect psychosis, plus review of family physician, psychiatric, and psychology case notes were undertaken at two time points, 2 years apart.

RESULTS

Point prevalence is 2.6% (95% CI = 1.8-3.8%) to 4.4% (95% CI = 3.2-5.8%), dependant upon the diagnostic criteria employed. Two-year incidence is 1.4% (95% CI = 0.6-2.6), and for first episode is 0.5% (95% CI = 0.1-1.3). Compared with the general population, the standardised incidence ratio for first episode psychosis is 10.0 (95% CI = 2.1-29.3). Full remission after 2 years is 14.3%. Visual impairment, previous long-stay hospital residence, smoking, and not having epilepsy were independently associated with psychosis, whereas other factors relevant to the general population were not.

CONCLUSIONS

The study of psychosis in persons with intellectual disabilities benefits the population with intellectual disabilities, and advances the understanding of psychosis for the general population. Mental health professionals need adequate knowledge in order to address the high rates of psychosis in this population.

The impact of inter-generational social and regional circumstances on dietary intake patterns of British adults: results from the 1946 British Birth Cohort

Objectives:

(1) To determine the extent to which an individual's childhood social circumstances and region of residence influence their dietary pattern at age 43 years and (2) to establish the extent to which an individual adopts the dietary pattern of their social and regional circumstances at age 43 years.

Design:

Longitudinal study of a social class stratified, random sample of all legitimate, singleton births in the week of 3–9 March 1946.

Settings:

England, Scotland and Wales.

Subjects:

The 3187 survey members who provided sociodemographic information at age 4 years in 1950 and sociodemographic and dietary data (48-hour dietary recall) at 43 years in 1989.

Results:

People who remained in the non-manual social class consumed significantly higher amounts of food items correlated with the factor health aware (items include high-fibre breakfast cereals, wholemeal breads, apples and bananas) than those who remained in the manual social class. Those who made the transition from manual social class in childhood to non-manual social class at age 43 years partly adopted the distinctive dietary patterns of the non-manual social classes. Consumption of items in the factors refined (items include whole-fat milk, white bread, sugar and butter) and sandwich (items include tomatoes, lettuce, onions, bacon and ham) did not differ by social class or regional mobility.

Conclusions:

This work suggests that although adult dietary patterns are developed as a result of childhood influences, these patterns can be modified as a result of social and regional transitions. Such changes in dietary patterns may influence susceptibility to disease.

Improvements in social functioning reported by a birth cohort in mid-adult life: A person-centred analysis of GHQ-28 social dysfunction items using latent class analysis

The General Health Questionnaire is widely used to measure the health status of individuals. Most studies have focused on traditional score values for one or more dimensions of psychopathology. We introduce a new analysis model that is person-centred and uses a latent structure approach to group individuals by a discrete latent variable. Data were drawn from a midlife (age 53) follow up of a national birth cohort study (n = 3035). For both men and women, three groups (latent classes) were sufficient to summarise individuals’ reports of recent changes in social functioning. The groups differed in the number and nature of the reported changes. Furthermore, they were shown to differ in terms of: (1) reported general health, (2) in mean scores on the conventional GHQ factors and (3) in several other variables external to the GHQ (happiness in job, ability to express feelings and self-confidence). Latent Class Analysis of positively worded GHQ items defined groups who differ in perceptions of recent positive changes in social functioning. These groups extend the value of individual health profiles afforded by the GHQ by using distinctions between categories in the first and second responses that are usually combined.

Validity of age at menarche self-reported in adulthood

OBJECTIVE

To test the validity of age at menarche self-reported in adulthood and examine whether socioeconomic position, education, experience of gynaecological events and psychological symptoms influence the accuracy of recall.

DESIGN

Prospective birth cohort study.

SETTING

England, Scotland and Wales.

PARTICIPANTS

1050 women from the Medical Research Council National Survey of Health and Development, with two measures of age at menarche, one recorded in adolescence and the other self-reported at age 48 years.

RESULTS

By calculating the limits of agreement, kappa statistic and Pearson's correlation coefficients (r), we found that the validity of age at menarche self-reported in middle age compared with that recorded in adolescence was moderate (kappa = 0.35, r = 0.66, n = 1050). Validity was improved by categorising age at menarche into three groups: early, normal and late (kappa = 0.43). Agreement was influenced by educational level and having had a stillbirth or miscarriage.

CONCLUSIONS

The level of validity shown in this study throws some doubt on whether it is justifiable to use age at menarche self-reported in middle age. It is likely to introduce error and bias, and researchers should be aware of these limitations and use such measures with caution.

Social circumstances and education: life course origins of social inequalities in metabolic risk in a prospective national birth cohort

OBJECTIVES

We investigated the relative importance of education and childhood and adult social class in the risk of metabolic syndrome.

METHODS

We conducted a prospective birth cohort study of 1311 men and 1318 women aged 53 years in 1999, when metabolic syndrome components were measured. Logistic regression analyses were used to calculate relative index of inequality estimates.

RESULTS

Relative to men and women at the highest education levels, men (odds ratio [OR]=2.0; 95% confidence interval [CI]=1.2, 3.2) and women (OR=2.7; 95% CI=1.5, 4.6) with the least education were at twice the risk or more of having the metabolic syndrome. Adjustment for childhood and adult social class strengthened this result among men and weakened it among women. Childhood social class was independently associated with the metabolic syndrome in women (OR=2.0; 95% CI=1.1, 3.6) but not in men (OR=1.1; 95% CI= 0.7, 1.8). Associations between adult social class and the metabolic syndrome or its components were largely accounted for by childhood socioeconomic measures.

CONCLUSIONS

Educational differences should be considered in the design of interventions aimed at reducing the burden of the metabolic syndrome in socially disadvantaged groups.

Three decades of antidepressant, anxiolytic and hypnotic use in a national population birth cohort

BACKGROUND

Psychotropic medication use is common and increasing. Use of such drugs at the individual level over long periods has not been reported.

AIMS

To describe antidepressant, anxiolytic and hypnotic drug use, and associations between such medication use and common mental disorder, over a 22-year period.

METHOD

Questions about psychotropic medication use and symptoms of common mental disorder were asked of more than 3000 members of the 1946 British birth cohort at multiple time points between ages 31 and 53 years.

RESULTS

Prevalence of any antidepressant, anxiolytic or hypnotic use increased significantly from 1977 (30.6 per 1000) to 1999 (59.1 per 1000) as the cohort aged. Less than 30% with mental disorder used antidepressants, anxiolytics or hypnotics. Previous use of antidepressant, anxiolytic or hypnotic was a strong predictor of future use during an episode of mental disorder (odds ratios 3.0-8.4); this association became weaker over time.

CONCLUSIONS

Pharmacotherapy is infrequently used by individuals with common mental disorder in Britain; this has not changed in the past three decades.

Do treated psychiatric patients become later community cases? A prospective cohort study

BACKGROUND

There have been few attempts to link two aspects of psychiatric epidemiology, severe disorder and milder 'common' mental disorder, by ascertaining whether subjects who have received psychiatric treatment for major disorders are identified later in epidemiological community surveys.

METHODS

Subjects were from a national birth cohort study and had been followed prospectively from childhood to middle age, with concurrent information on treatment from psychiatric facilities. In two successive prevalence surveys of milder disorder at 36 and 43 years, the association between earlier treatment and being a later community case was examined

RESULTS

Among 102 subjects who had been treated patients up to age 35 years, 52 (51%) were identified as definite community cases (36, 35%) or subthreshold cases (16, 16%) at either one or both later points. The proportion of community subjects who were previous psychiatric patients increased systematically from community non-cases, through subthreshold cases on one or both occasions, definite cases on one occasion, to definite cases on both occasions.

CONCLUSIONS

About half of subjects who have received treatment from psychiatric facilities remain with persistent symptoms such as to identify them as definite or subthreshold cases of milder common mental disorder some years later.

Young adult outcomes of very-low-birth-weight children

Information on the young adult outcomes of the initial survivors of neonatal intensive care has been reported from the United States, Canada, Australia, Great Britain and other European countries. The studies have varied with regard to whether they were regional or hospital-based, their birth-weight group and gestational age, rates of survival, socio-demographic background, and measures of assessment and types of outcome studied. Despite these differences the overall results reveal that neurodevelopment and growth sequelae persist to young adulthood. Very-low-birth-weight young adults have, with few exceptions, poorer educational achievement than normal-birth-weight controls, and fewer continue with post-high-school study. Rates of employment are, however, similar. There are no major differences in general health status, but the young adults demonstrate poorer physical abilities, higher mean blood pressure and poorer respiratory function. There is no evidence of major psychiatric disorder, although anxiety and depression are reported more often. The young adults report less risk-taking than control populations. They report fairly normal social lives and quality of life. When differences are noted they are usually due to neurosensory disabilities. Longer-term studies are needed to evaluate ultimate educational and occupational achievement. It will also be important to assess the effects of preterm birth, early growth failure and catch-up growth on later metabolic and cardiovascular health.

Statistical issues in life course epidemiology

There is growing recognition that the risk of many diseases in later life, such as type 2 diabetes or breast cancer, is affected by adult as well as early-life variables, including those operating prior to conception and during the prenatal period. Most of these risk factors are correlated because of common biologic and/or social pathways, while some are intrinsically ordered over time. The study of how they jointly influence later ("distal") disease outcomes is referred to as life course epidemiology. This area of research raises several issues relevant to the current debate on causal inference in epidemiology. The authors give a brief overview of the main analytical and practical problems and consider a range of modeling approaches, their differences determined by the degree with which associations present (or presumed) among the correlated explanatory variables are explicitly acknowledged. Standard multiple regression (i.e., conditional) models are compared with joint models where more than one outcome is specified. Issues arising from measurement error and missing data are addressed. Examples from two cohorts in the United Kingdom are used to illustrate alternative modeling strategies. The authors conclude that more than one analytical approach should be adopted to gain more insight into the underlying mechanisms.

Parent-child relationships and health problems in adulthood in three UK national birth cohort studies

BACKGROUND

Event-based measures suggest that emotional adversity in childhood has a long-term health impact, but less attention has been paid to chronic emotional stressors such as family conflict, harsh discipline or lack of affection. This study aimed to assess the impact of the latter on health problems and illness in adulthood.

METHODS

Logistic regression and multinomial logistic regression analyses of data collected in three UK national birth cohort studies at ages 43 and 16 years covering subjective report of relationship quality from the 'child', and number of health problems and illnesses reported in adulthood at ages 43, 33 and 26 years adjusted for social class, sex and, in 1946 and 1970 cohorts, for symptoms of mental illness.

RESULTS

Reports of abuse and neglect (1946 cohort), poor quality relationship with mother and father (1958 cohort), and a range of negative relationship descriptors (1970 cohort) predicted reports of three or more illnesses or health problems in adulthood. Results were inconsistent with respect to one or two illnesses or health problems. Adjustment for sex, social class and poor mental health attenuated the odds of poor health, but measures of relationship quality retained a significant independent effect.

CONCLUSIONS

Poor quality parent-child relationships could be a remediable risk factor for poor health in adulthood.