Participants Who Left a Multiple-Wave Cohort Study Had Similar Baseline Characteristics to Participants Who Returned

The Association between Body Weight Misclassification in Adolescence and Body Fat and Waist Circumference in Adulthood: A Longitudinal Study

This study examined the longitudinal association between adolescent body weight misclassifications and body fat and waist circumference during adulthood. A sample was derived from a large Australian birth cohort study. The data analyses were restricted to 1002 participants for whom data on both measured and perceived weight at a 14-year follow-up and the actual measure of adult body fat and waist circumference at a 30-year follow-up were available. To determine misclassifications, we compared the perceived weight with the measured weight. The results were presented as means and mean differences (with a 95% confidence interval) of the body fat percentages and waist circumference levels across the weight misclassification groups, adjusting for potential covariates. For both male and female adolescents, weight underestimation was significantly associated with an increase in body fat percentages and waist circumference in adulthood as compared to those who correctly estimated their weight. In the mean difference analyses, adolescent males and females who underestimated their weight were found to have significantly higher body fat, and waist circumference means than those who correctly estimated their weight in the unadjusted and adjusted comparisons. The adolescent males who overestimated their weight had higher body fat, and waist circumference means when they reached adulthood. Increased awareness of weight misclassification and actual weight among adolescents might contribute to better control of weight gain in adulthood.

Strategies for assessing the impact of loss to follow-up on estimates of neurodevelopmental impairment in a very preterm cohort at 2 years of age

BACKGROUND

Loss to follow-up is a major challenge for very preterm (VPT) cohorts; attrition is associated with social disadvantage and parents with impaired children may participate less in research. We investigated the impact of loss to follow-up on the estimated prevalence of neurodevelopmental impairment in a VPT cohort using different methodological approaches.

METHODS

This study includes births < 32 weeks of gestational age (GA) from 4 regions in the UK and Portugal participating in a European birth cohort (N = 1737 survivors). Data on maternal characteristics, pregnancy complications, neonatal outcomes and neighborhood deprivation were collected at baseline. Neurodevelopment was assessed at 2 years of corrected age (CA) using standardized parent-report measures. We applied (1) multiple imputation (MI) and (2) inverse probability weighting (IPW) to estimate the impact of non-response on the prevalence of moderate to severe neurodevelopmental impairment and assessed violations of the missing at random (MAR) assumption using the delta method.

RESULTS

54.2% of children were followed-up. Follow-up was less likely when mothers were younger, multiparous, foreign-born, did not breastfeed and came from deprived areas. The prevalence of neurodevelopmental impairment was 18.4% (95% confidence interval (CI):15.9-21.1) and increased to 20.4% (95%CI: 17.3-23.4) and 20.0% (95%CI:16.9-23.1) for MI and IPW models, respectively. Simulating strong violations of MAR (children with impairments being 50% less likely to be followed-up) raised estimates to 23.6 (95%CI:20.1-27.1) CONCLUSIONS: In a VPT cohort with high loss to follow-up, correcting for attrition yielded modest increased estimates of neurodevelopmental impairment at 2 years CA; estimates were relatively robust to violations of the MAR assumption.

Income, Gender, and Forms of Intimate Partner Violence

Poverty and socioeconomic disadvantage place demands on intimate relationships and provide fertile ground for disagreements and conflicts. It is not known whether poverty also leads to intimate partner violence (IPV). This study investigates the association between income and forms of IPV victimization for both males and females. We also examine whether income inequalities are related to IPV and whether the gender balance of household income contributes to IPV victimization. Data are from a cohort of 2,401 young offspring (60.3% females) who participated at the 30-year follow-up of the Mater-University of Queensland Study of Pregnancy in Brisbane, Australia. Participants completed questionnaires including their income details and the Composite Abuse Scale. Within low-income families, both partners experience higher levels of IPV. Females' income is not independently related to experiencing IPV either for females or males. Females and males experience a higher rate of IPV when the husband earns a low income. When considering partners' relative income, families in which both partners earned a low income experienced higher levels of almost all forms of IPV. Income (im)balance in which females earn more or partners both have higher income was less often associated with the experience OF IPV IPV appears to be mutually experienced in the setting of the poverty. Objective economic hardship and scarcity create a context which facilitates IPV for both partners in a relationship.

Illicit drug use by mothers and their daughters in Australia: A comparison of two generations

BACKGROUND

While recent decades have witnessed an increase in the use of illicit drugs in Australia, the extent to which the types of drugs used has changed over a generation of young women has not been documented.

METHODS

Data are from a prospective birth cohort study. Mothers were recruited in early pregnancy (1981-83) and then they and their child were followed up, with mothers interviewed 27 years (2008-2011), and daughters 30 years (2010-14), after the birth. At these most recent interviews both mothers and daughters were administered the Composite International Diagnostic Interview (CIDI III). Comparisons are for mothers and daughters separated by a 25 year period. For this study, we compare levels of lifetime use of a range of illicit drugs and drug use disorders reported by mothers and their daughters (N = 998 mother/daughter pairs) with adjustment for family income, marital status, education and occupation.

RESULTS

There has been a generational increase in the use of illicit substances and prevalence of substance use disorders experienced by Australian women. Mothers' use of illicit drugs was generally restricted to cannabis. By contrast the majority of daughters report lifetime use of an illicit drug with cannabis, club drugs and stimulants the most common. Compared to the mothers, daughters used club drugs 50 times, cocaine 19 times and inhalants 20 times more often. Daughters report experiencing 12 times the rate of cocaine use disorders, 9 times the rate of stimulant disorders and 7 times the rate of cannabis use disorders compared to their mothers.

CONCLUSIONS

Mothers of the current generation of 30 year old Australian women rarely used illicit drugs and few experienced a drug use disorder. The current generation of young women report commonly using one or more illicit drugs with a substantial minority experiencing a drug use disorder. It is unlikely that the use of illicit drugs by young women in Australia will be reversed in the foreseeable future. Government policies and treatment practices need to be calibrated to the reality of the much greater contact with illicit drugs being exhibited by younger women.

'Telling our story... Creating our own history': caregivers' reasons for participating in an Australian longitudinal study of Indigenous children

BACKGROUND

Improving the wellbeing of Indigenous populations is an international priority. Robust research conducted with Aboriginal and Torres Strait Islander peoples is key to developing programs and policies to improve health and wellbeing. This paper aims to quantify the extent of participation in a national longitudinal study of Aboriginal and Torres Strait Islander (Indigenous Australian) children, and to understand the reasons why caregivers participate in the study.

METHODS

This mixed methods study uses data from Wave 6 of Footprints in Time, the Longitudinal Study of Indigenous Children. We conducted descriptive analysis of quantitative variables to characterise the sample and retention rates. We applied conventional content analysis to 160 caregivers' open-ended responses to the question, 'Why do you stay in the study?', identifying themes and overarching meta-themes.

RESULTS

The study has maintained a high retention rate, with 70.4% (n = 1239/1671) of the baseline sample participating in the study's 6th wave. We identified seven themes related to why participants stay in the study: telling our story, community benefit, satisfaction, tracking Study Child's progress, study processes, receiving study gifts, and valuing what the study stands for. These related to two meta-themes: reciprocity, and trust and connection. Caregivers reported that participation was associated with benefits for their family and community as well as for the study. They identified specific features of the Footprints in Time study design that built and maintained trust and connection between participants and the study.

CONCLUSIONS

Our findings support the assertion that Aboriginal and Torres Strait Islander people want to be involved in research when it is done 'the right way'. Footprints in Time has successfully recruited and retained the current-largest cohort of Aboriginal and Torres Strait Islander children in Australia through the use of participatory research methodologies, suggesting effective study implementation and processes. Participants indicated ongoing commitment to the study resulting from perceptions of reciprocity and development of trust in the study. Footprints in Time can serve as a successful model of Aboriginal and Torres Strait Islander health research, to promote good research practice and provides lessons for research with other Indigenous populations.

Simple descriptive missing data indicators in longitudinal studies with attrition, intermittent missing data and a high number of follow-ups

Objective

Missing data in longitudinal studies may constitute a source of bias. We suggest three simple missing data indicators for the initial phase of getting an overview of the missingness pattern in a dataset with a high number of follow-ups. Possible use of the indicators is exemplified in two datasets allowing wave nonresponse; a Norwegian dataset of 420 subjects examined at 21 occasions during 6.5 years and a Dutch dataset of 350 subjects with ten repeated measurements over a period of 35 years.

Results

The indicators Last response (the timing of last response), Retention (the number of responded follow-ups), and Dispersion (the evenness of the distribution of responses) are introduced. The proposed indicators reveal different aspects of the missing data pattern, and may give the researcher a better insight into the pattern of missingness in a study with several follow-ups, as a starting point for analyzing possible bias. Although the indicators are positively correlated to each other, potential predictors of missingness can have a different relationship with different indicators leading to a better understanding of the missing data mechanism in longitudinal studies. These indictors may be useful descriptive tools when starting to look into a longitudinal dataset with many follow-ups.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3228-6) contains supplementary material, which is available to authorized users.

Mother-adult offspring resemblance in dietary intake: a community-based cohort study in Australia

BACKGROUND

It has been widely recognized that parental dietary intake is an important and consistent factor influencing children's food intake. However, there are conflicting results with regard to the strength of the parental-child resemblance in dietary intake. Moreover, this association has rarely been investigated in young adult offspring.

OBJECTIVES

The aims of this study were to describe the dietary intake and food consumption of middle-aged women and their female and male adult offspring (aged 18-23 y) and to examine the association in dietary intake between sex-specific mother-child dyads.

DESIGN

We used cross-sectional dietary data for 2017 mother-child pairs from the 21-y follow-up of the Mater-University of Queensland Study of Pregnancy, a birth cohort study. Dietary information was obtained with the use of a 74-item food-frequency questionnaire. We assessed multivariate-adjusted mother-offspring correlations in selected nutrients and food groups and performed correlational analysis while stratifying by living arrangements.

RESULTS

Both sons and daughters had a significantly lower percentage of energy from protein than did their mothers. Sons had a significantly higher percentage of energy from fat and a lower percentage of energy from carbohydrates than did their mothers, whereas there was no difference between daughters and mothers. The mother-offspring correlations were weak (r = 0.12-0.29) for most dietary factors and tended to be slightly higher in mother-daughter dyads than in mother-son dyads. Overall, correlations appeared to be stronger in offspring still living with their parents than with their counterparts not living at home, specifically the correlations for consumption of vegetables and rice.

CONCLUSIONS

Mother-adult offspring dietary resemblance in this Australian cohort was only weak and varied by nutrients, food groups, and the offspring's sex and living arrangements. Factors other than parental dietary habits and home environment seem to have a stronger influence on the diets of young adults.

Parental pre-pregnancy BMI influences on offspring BMI and waist circumference at 21 years

OBJECTIVES

To investigate the prospective association between parental pre-pregnancy BMI and adult male and female offspring BMI and waist circumference (WC).

METHODS

Sub-sample of 2,229 parent-offspring pairs with parental pre-pregnancy BMI and offspring BMI and WC at 21 years were used from the MUSP (Mater-University of Queensland Study of Pregnancy cohort). Multivariable results were adjusted for maternal factors around pregnancy (e.g. gestational weight and smoking during pregnancy) and offspring factors in early life (e.g. birth weight) and at 14 years (e.g. sports participation and mealtime with family).

RESULTS

After adjustments for confounders, each unit increase in paternal and maternal BMI, the BMI of young adult offspring increased by 0.33kg/m² and 0.35kg/m² , and the WC increased by 0.76 cm and 0.62 cm, respectively. In the combination of parents' weight status, offspring at 21 years were six times the risk being overweight/obese (OW/OB) when both parents were OW/OB, compared to offspring of healthy weight parents.

CONCLUSIONS

Prenatal parental BMI are independently related to adult offspring BMI and WC.

IMPLICATIONS

Both prenatal paternal-maternal weight status are important determinants of offspring weight status in long-term. Further studies are warranted to investigate the underlying mechanisms.

Factors relating to participation in follow-up to the 45 and up study in Aboriginal and non-Aboriginal individuals

BACKGROUND

This study aimed to characterise the factors relating to participation in a postal follow-up study in Aboriginal and non-Aboriginal individuals, given the need to quantify potential biases from loss to follow-up and the lack of evidence regarding postal surveys among Aboriginal people.

METHODS

The first 100,000 participants from the Sax Institute's 45 and Up Study, a large scale cohort study, were posted a follow-up questionnaire gathering general demographic, health and risk factor data, emphasising Social, Economic and Environmental Factors ("The SEEF Study"). For each variable of interest, percentages of those invited who went on to participate in follow-up were tabulated separately for Aboriginal and non-Aboriginal participants and age- and sex-adjusted participation rate ratios (aPRR) were calculated.

RESULTS

Of the 692 Aboriginal and 97,178 non-Aboriginal invitees to the study, 314 Aboriginal (45 %) and 59,175 non-Aboriginal (61 %) individuals responded. While Aboriginal people were less likely to respond than non-Aboriginal people (aPRR 0.72, 95 % CI 0.66-0.78), factors related to response were similar. Follow-up study participants were more likely than non-participants to have university versus no educational qualifications (1.6, 1.3-2.0 [Aboriginal]; 1.5, 1.5-1.5 [non-Aboriginal]) and an annual income of ≥70,000 versus < $20,000 (1.6, 1.3-2.0; 1.2, 1.2-1.3 [χ (2) = 7.7; p = 0.001]). Current smokers (0.55, 0.42-0.72; 0.76, 0.74-0.77 [χ (2) = 7.14; p = 0.03]), those reporting poor self-rated health (0.68, 0.47-0.99; 0.65, 0.61-0.69), poor quality of life (0.63, 0.41-0.97; 0.61, 0.57-0.66) and very high psychological distress (0.71, 0.68-0.75 [non-Aboriginal]) were less likely than other cohort members to respond.

CONCLUSIONS

Relatively large numbers of Aboriginal and non-Aboriginal individuals participated in the first 45 and Up Study follow-up suggesting that postal surveys can be used to follow Aboriginal participants in cohort studies. Despite somewhat greater loss to follow-up in Aboriginal people (after considering socio-demographic and health characteristics), factors related to follow-up participation were similar in both groups: greater loss was observed in those experiencing disadvantage, ill-health and health risk, with implications for interpretation of future findings. Aboriginal low income earners and current regular smokers had a particularly elevated likelihood of non-participation compared to non-Aboriginal people. These findings highlight the importance of identifying and addressing barriers to participation among hard-to-reach population groups.

The association between perception of health during pregnancy and the risk of cardiovascular disease: a prospective study

There is some evidence that self-rated perceptions of health are predictive of objective health outcomes, including cardiovascular disease, and mortality. The objective of this study was to examine the prospective association between perceptions of health during pregnancy and cardiovascular risk factors of mothers 21 years after the pregnancy. Data used were from the Mater University Study of Pregnancy (MUSP), a community-based prospective birth cohort study begun in Brisbane, Australia, in 1981. Logistic regression analyses were conducted. Data were available for 3692 women. Women who perceived themselves as not having a straight forward pregnancy had twice the odds (adjusted OR 2.0, 95 % CI 1.1–3.8) of being diagnosed with heart disease 21 years after the pregnancy when compared with women with a straight forward pregnancy (event rate of 5.2 versus 2.6 %). Women who experienced complications (other than serious pregnancy complications) during their pregnancy were also at 30 % increased odds (adjusted OR 1.3, 95 % CI 1.0–1.6) of having hypertension 21 years later (event rate of 25.7 versus 20 %). As a whole, our study suggests that pregnant women who perceived that they had complications and did not have a straight forward pregnancy were likely to experience poorer cardiovascular outcomes 21 years after that pregnancy.

Do Participants With Different Patterns of Loss to Follow-Up Have Different Characteristics? A Multi-Wave Longitudinal Study

Background

To identify patterns of loss to follow-up and baseline predictors of each pattern.

Methods

The Mater-University Study of Pregnancy collected baseline information for 7718 pregnant women who attended Mater Hospital in Brisbane, Australia, from 1981 through 1983. Follow-up data for 6753 eligible participants were collected at 6 months, 5 years, 14 years, 21 years, and 27 years after giving birth. Participants were partitioned into groups of ‘Always Responders’, ‘Returners’, ‘Leavers’, ‘Intermittents’, and ‘Never Responders’. Multinomial logistic regression was used to simultaneously compare baseline characteristics of the last four groups with ‘Always Responders’.

Results

Being younger, less educated, having no partner, and living in rented housing were associated with being a ‘Returner’. Not owning housing, receiving welfare benefits, and being younger, less educated, not married, a smoker, an Aboriginal/Islander, and born in a non-English-speaking country were associated with being a ‘Leaver’, an ‘Intermittent’, or a ‘Never-responder’. Having higher mental health score and drinking before pregnancy were associated with being a ‘Leaver’ or an ‘Intermittent’. Being unemployed and not physically active were associated with being a ‘Leaver’ or ‘Never Responder’. The groups ‘Leavers’ and ‘Never Responders’ were the most different from the ‘Always Responders’. The group that was most similar to ‘Always Responders’ was the ‘Returners’.

Conclusions

Patterns of loss to follow-up should be considered in the application of missing data techniques, where researchers make assumptions about the characteristics of those subjects who do not respond to assess the type of missing data. This information can be used to prevent individuals who are at high risk of dropping out of a study from doing so.

Anxiety symptoms and the risk of diabetes mellitus in Australian women: evidence from 21-year follow-up

OBJECTIVES

This study aimed to explore the association between transitions in anxiety symptoms and the risk of diabetes in women, using longitudinal data.

STUDY DESIGN

This longitudinal study measured diabetes, and transitions in anxiety symptoms, using validated instruments.

METHODS

Data obtained by the Mater-University of Queensland Study of Pregnancy were analysed. Anxiety was measured using the Delusion Symptoms States Inventory (DSSI). To examine possible transitions over different time periods, anxiety was grouped into four categories and assessed at different phases over a 21-year period.

RESULTS

Three hundred and one women reported diabetes 21 years after the index pregnancy. Almost half of the women who reported anxiety symptoms continued to report these at a subsequent follow-up (FU) phase. About 1 in 10 women who had not reported anxiety symptoms at 5-year FU did so at the subsequent 14-year FU. In prospective analyses, we did not find significant association of diabetes with negative transition (no anxiety to anxiety at subsequent phase) or with positive history of anxiety symptom, but an increasing risk was evident. Women with persistent symptoms had a 1.85-fold greater risk of diabetes (95% CI: 1.18-2.90). The cross-sectional analysis did not produce significant results.

CONCLUSIONS

Despite some limitations, this study provides insight into the long-term association between events of anxiety and the risk of diabetes across the reproductive life of women. However, the evidence is not strong enough to support a direct effect of anxiety in causing diabetes.

Demographic and psychological predictors of panel attrition: evidence from the New Zealand attitudes and values study

This study examines attrition rates over the first four years of the New Zealand Attitudes and Values Study, a longitudinal national panel sample of New Zealand adults. We report the base rate and covariates for the following four distinct classes of respondents: explicit withdrawals, lost respondents, intermittent respondents and constant respondents. A multinomial logistic regression examined an extensive range of demographic and socio-psychological covariates (among them the Big-Six personality traits) associated with membership in these classes (N = 5,814). Results indicated that men, Māori and Asian peoples were less likely to be constant respondents. Conscientiousness and Honesty-Humility were also positively associated with membership in the constant respondent class. Notably, the effect sizes for the socio-psychological covariates of panel attrition tended to match or exceed those of standard demographic covariates. This investigation broadens the focus of research on panel attrition beyond demographics by including a comprehensive set of socio-psychological covariates. Our findings show that core psychological covariates convey important information about panel attrition, and are practically important to the management of longitudinal panel samples like the New Zealand Attitudes and Values Study.

Cohort Profile Update: The Mater-University of Queensland Study of Pregnancy (MUSP)

The Mater-University of Queensland Study of Pregnancy (MUSP) and its outcomes began in 1981 with data collected on 7223 pregnant woman-child pairs (6753 mothers, of whom 520 had 2 study children, less 50 who had multiple births). These women, and their children, were initially followed for up to 21 years. Since then there have been additional follow-ups of the mothers (27 years) and their children (30 years). There has also been a substantial increase in the breadth of topics addressed, with the collection of biological samples, the administration of structured clinical assessments of mental health and cognitive capacity, and markers of physical health such as lung function and blood pressure. MUSP was originally developed as a birth cohort study. It has become a longitudinal study of growth, development and ageing with an emphasis on the generational transmission of a wide range of factors impacting on adult health outcomes. We welcome interest in our study; for study background and publications visit [www.socialscience.uq.edu.au/musp] or contact [j.najman@uq.edu.au].

Long-term outcomes of infant behavioral dysregulation

OBJECTIVES

To determine whether maternal report of infant behavioral dysregulation at 6 months is associated with a higher prevalence of behavioral concerns at 5, 14, and 21 years of age; and to assess the extent to which maternal and social factors may affect reported child behavior outcomes.

METHODS

From the Mater-University of Queensland Study of Pregnancy cohort of 7223 live singleton babies, information on dysregulation was available for 6389 children at 6 months. Of those children, behavior data were available for 4836 at 5 years by using a modified Child Behavior Checklist, 4746 at 14 years by using a full Child Behavior Checklist and Youth Self-Report, and 3558 at 21 years by using a Young Adult Self-Report. Of the youth with dysregulation data at 6 months, 2308 completed the Composite International Diagnostic Interview at 21 years. Potential confounding and mediating factors were analyzed by using logistic regression.

RESULTS

Maternal-reported behavioral dysregulation at 6 months was associated with a significantly higher prevalence of maternal-reported behavior problems at 5 and 14 years (P < .001), but not youth self-reported problems at 14 or 21 years, or Composite International Diagnostic Interview-Diagnostic and Statistical Manual diagnoses at 21 years. The strength of association between infant dysregulation and maternal-reported behaviors was greater at 5 years than at 14 years, and was substantially reduced by adjusting for maternal, social, and infant factors, especially potentially the mediating factors of maternal anxiety and depression.

CONCLUSIONS

Infant behavioral dysregulation was a risk factor for maternal-reported behavior concerns at 5 and 14 years, although was unrelated to young adult mental health.

Who does not participate in a follow-up postal study? a survey of infertile couples treated by in vitro fertilization

Background

A good response rate has been considered as a proof of a study’s quality. Decreasing participation and its potential impact on the internal validity of the study are of growing interest. Our objective was to assess factors associated with contact and response to a postal survey in a epidemiological study of the long-term outcome of IVF couples.

Methods

The DAIFI study is a retrospective cohort including 6,507 couples who began an IVF program in 2000-2002 in one of the eight participating French IVF centers. Medical data on all 6,507 couples were obtained from IVF center databases, and information on long-term outcome was available only for participants in the postal survey (n = 2,321). Logistic regressions were used to assess firstly factors associated with contact and secondly factors associated with response to the postal questionnaire among contacted couples.

Results

Sixty-two percent of the 6,507 couples were contacted and 58% of these responded to the postal questionnaire. Contacted couples were more likely to have had a child during IVF treatment than non-contactable couples, and the same was true of respondents compared with non-respondents. Demographic and medical characteristics were both associated with probability of contact and probability of response. After adjustment, having a live birth during IVF treatment remained associated with both probabilities, and more strongly with probability of response. Having a child during IVF treatment was a major factor impacting on participation rate.

Conclusions

Non-response as well as non-contact were linked to the outcome of interest, i.e. long-term parenthood success of infertile couples. Our study illustrates that an a priori hypothesis may be too simplistic and may underestimate potential bias. In the context of growing use of analytical methods that take attrition into account (such as multiple imputation), we need to better understand the mechanisms that underlie attrition in order to choose the most appropriate method.

Predicting depressive and anxiety disorders with the YASR internalising scales (empirical and DSM-oriented)

BACKGROUND

The Achenbach problem behaviour scales (CBCL/YSR) are widely used. The DSM-oriented anxiety and depression scales have been created to improve concordance between Achenbach's internalising scales and DSM-IV depression and anxiety. To date no study has examined the concurrent utility of the young adult (YASR) internalising scales, either the empirical or newly developed DSM-oriented depressive or anxiety scales.

METHODS

A sample of 2,551 young adults, aged 18-23 years, from an Australian cohort study. The association between the empirical and DSM-oriented anxiety and depression scales were individually assessed against DSM-IV depression and anxiety diagnoses derived from structured interview. Odds ratios, ROC analyses and diagnostic efficiency tests (sensitivity, specificity, positive and negative predictive values) were used to report findings.

RESULTS

YASR empirical internalising scale predicted DSM-IV mood disorders (depression OR = 6.9, 95% CI 5.0-9.5; anxiety OR = 5.1, 95% CI 3.8-6.7) in the previous 12 months. DSM-oriented depressive or anxiety scales did not appear to improve the concordance with DSM-IV diagnosed depression or anxiety. The internalising scales were much more effective at identifying those with comorbid depression and anxiety, with ORs between 10.1 and 21.7 depending on the internalising scale used.

CONCLUSION

DSM-oriented scales perform no better than the standard internalising in identifying young adults with DSM-IV mood or anxiety disorder.

Assessing generalisability through the use of disease registers: findings from a diabetes cohort study

Objectives Knowledge of a study population's similarity to the target population allows researchers to assess the generalisability of their results. Often generalisability is assessed through a comparison of baseline characteristics between individuals who did and did not respond to an invitation to participate in a study. In this prospective population-based cohort, we broadened this assessment by comparing participants with all individuals from a chronic disease register who satisfied the study eligibility criteria but for a number of reasons, such as the absence of consent to be approached for research purposes, did not participate. Methods Data are from the Living with Diabetes Study, a population-based cohort of individuals diagnosed with diabetes mellitus, which commenced in Queensland, Australia in 2008. Individuals were sampled from a federally-funded diabetes register. We compared the characteristics of 3951 study participants with 10 488 non-participants (individuals who were invited to participate but declined) and with 129 900 non-study individuals on the register who did not participate in the study. Results Study participants were more likely than non-study registrants to be male, aged 50-69, have type 2 diabetes non-insulin requiring, be recently registered and be non-indigenous Australians. Study participants were more likely than non-participants to be aged 50-69, have type 1 diabetes and be non-indigenous Australians. Conclusions The interpretation of a study's generalisability can alter depending on which non-participating group is compared with participants. When assessing generalisability, participants should be compared with the largest possible group of non-participating individuals. When sampling from a disease register, researchers should be wary of the influence of research consent procedures on the register's coverage.

The link between sleep problems in infancy and early childhood and attention problems at 5 and 14 years: Evidence from a birth cohort study

BACKGROUND

Little research has examined the associations between early sleep problems and attention problems over several developmental periods.

AIMS

To examine whether sleep problems in infancy and early childhood are independently related to attention difficulty at 5 and 14 years, and to the continuity of attention difficulties from 5 to 14 years.

STUDY DESIGN

The study was a prospective, population-based birth cohort study.

SUBJECTS

7223 women who delivered a live, singleton child between 1981 and 1983 were recruited at the first antenatal visit. Of these, 4204 had complete information on all key measures.

OUTCOME MEASURES

Attention problems were assessed with items from the Child Behaviour Checklist (CBCL) and were classified as adolescent onset (i.e. problems at 14 but not at 5); early remitter (problems at 5, no problem at 14); and persistent (i.e. at both 5 and 14).

RESULTS

At 6 months, sleep problems 'sometimes' were associated with the early remitter group in boys. For sleep problems between 2 and 4 years of age, findings were generally similar for boys and girls with strong associations with adolescent attention. Sleep problems 'often' were independently associated with early remitter and persistent attention problems, and 'sometimes' with early remitter and adolescent onset attention problems.

CONCLUSIONS

Sleep problems in early childhood are an indicator of subsequent attention problems that may persist into adolescence. Whether these associations are causal requires further research, however their presence provides an opportunity for early intervention and monitoring.

Maternal depression and the quality of marital relationship: a 14-year prospective study

AIMS

This study aims to investigate the bidirectional association between symptoms of depression and quality of marital relationship in a population-based cohort of women.

METHODS

The bidirectional association was examined longitudinally in over 3694 women participating in the Mater-University study of Pregnancy, Brisbane, Australia, over a 14-year period. Women were interviewed 3-5 days postdelivery and again when the child was 6 months, 5 years, and 14 years of age. A transition model was developed to examine changes in exposures and risk factors over the 14 years of follow-up.

RESULTS

Nearly 40% of the women with depressive symptoms continued to report symptoms, and a similar proportion of women who reported being in a poor quality marital relationship remained in a poor quality relationship over long periods of time. Approximately 1 in 10 women who had not reported symptoms of depression or a poor relationship in the previous phase did so at the subsequent phase. The bidirectional relationships between depressive symptoms and quality of marital relationship are both consistent and strong. Negative changes in either symptoms of depression or quality of marital relationship predicted a poor outcome. The estimated population attributable risk was similar for both depressive symptoms and quality of the marital relationship.

CONCLUSIONS

The findings from this study suggest that symptoms of depression and quality of relationship are strongly associated with each other and that this association is bidirectional. Clinical intervention in poor quality marital relationships represents a logical approach to addressing symptoms of depression in women. Similarly, there needs to be a focus on family outcomes for those women with impaired mental health.

Childhood overweight status predicts diabetes at age 21 years: a follow-up study

We examined the prospective association of childhood BMI z-score and BMI categories (normal or overweight) with young adult diabetes, controlling for early life, childhood, and adolescence factors. A subsample of 2,639 young adults from the Mater-University study of pregnancy (MUSP) and its outcomes, a prospective birth cohort who were born in Brisbane, Australia and for whom we had measured height and weight at 5 years and self-reported diabetes at age 21 years. The risk of developing diabetes by age 21 years was greater among young adults who had greater BMI z-score or were overweight at age 5 years than those who had normal BMI at age 5 years. Young adults who were overweight at age 5 years had an increased odds ratio of 2.60 (95% confidence interval (CI): 1.29, 5.22, in age- and sex-adjusted model) of experiencing diabetes by age 21 years. Adjustment for potential confounders and mediators including intrauterine environmental factors, childhood dietary patterns, television watching, participation in sports and exercise, and current weight, did not substantively alter these associations. Overweight and increasing BMI z-score at childhood is an independent predictor of young adult's type 1 and type 2 diabetes. Findings of this study suggest that childhood BMI may be central to the development and rising incidence of all diabetes.

Determinants of subject visit participation in a prospective cohort study of HTLV infection

BACKGROUND

Understanding participation in a prospective study is crucial to maintaining and improving retention rates. In 1990-92, following attempted blood donation at five blood centers, we enrolled 155 HTLV-I, 387 HTLV-II and 799 HTLV seronegative persons in a long-term prospective cohort.

METHODS

Health questionnaires and physical exams were administered at enrollment and 2-year intervals through 2004. To examine factors influencing attendance at study visits of the cohort participants we calculated odds ratios (ORs) with generalized estimated equations (GEE) to analyze fixed and time-varying predictors of study visit participation.

RESULTS

There were significant independent associations between better visit attendance and female gender (OR = 1.31), graduate education (OR = 1.86) and income > $75,000 (OR = 2.68). Participants at two centers (OR = 0.47, 0.67) and of Black race/ethnicity (OR = 0.61) were less likely to continue. Higher subject reimbursement for interview was associated with better visit attendance (OR = 1.84 for $25 vs. $10). None of the health related variables (HTLV status, perceived health status and referral to specialty diagnostic exam for potential adverse health outcomes) significantly affected participation after controlling for demographic variables.

CONCLUSION

Increasing and maintaining participation by minority and lower socioeconomic status participants is an ongoing challenge in the study of chronic disease outcomes. Future studies should include methods to evaluate attrition and retention, in addition to primary study outcomes, including qualitative analysis of reasons for participation or withdrawal.

Characteristics of nonparticipants differed based on reason for nonparticipation: a study involving the chronically ill

BACKGROUND

Individuals who do and do not participate in studies often have different characteristics. The profile of nonparticipants may vary by type of nonparticipation. Few cross-sectional or longitudinal studies of chronically ill individuals identify these differences at baseline and of those that do; many do not have information on type of nonparticipation. We compared characteristics of chronically ill individuals to determine if they differ by type of nonparticipation.

METHODS

Data are from an evaluation of a chronic disease management program conducted in New South Wales, Australia during 2001 and 2002. Characteristics were compared using routinely collected hospital data. Reasons for nonparticipation were categorized as refusal, death, or untraceable.

RESULTS

Individuals who refused to participate were older, female, discharged at risk, and have heart failure. Those untraceable were younger, not married, Indigenous, and receiving care during the intervention phase but not recruited. Individuals not participating due to death were older, male, not cohabiting, discharged at risk, and have a diagnosis of cancer or heart failure.

CONCLUSION

The significant differences between untraceable, refused, and deceased individuals should be considered when designing studies and when adjusting for nonparticipation bias.