Childhood mental ability and smoking cessation in adulthood: prospective observational study linking the Scottish Mental Survey 1932 and the Midspan studies

The shared genetic architecture of smoking behaviours and psychiatric disorders: evidence from a population-based longitudinal study in England

BACKGROUND

Considering the co-morbidity of major psychiatric disorders and intelligence with smoking, to increase our understanding of why some people take up smoking or continue to smoke, while others stop smoking without progressing to nicotine dependence, we investigated the genetic propensities to psychiatric disorders and intelligence as determinants of smoking initiation, heaviness of smoking and smoking cessation in older adults from the general population.

RESULTS

Having utilised data from the English Longitudinal Study of Ageing (ELSA), our results showed that one standard deviation increase in MDD-PGS was associated with increased odds of being a moderate-heavy smoker (odds ratio [OR] = 1.11, SE = 0.04, 95%CI = 1.00-1.24, p = 0.028). There were no other significant associations between SZ-PGS, BD-PGS, or IQ-PGS and smoking initiation, heaviness of smoking and smoking cessation in older adults from the general population in the UK.

CONCLUSIONS

Smoking is a behaviour that does not appear to share common genetic ground with schizophrenia, bipolar disorders, and intelligence in older adults, which may suggest that it is more likely to be modifiable by smoking cessation interventions. Once started to smoke, older adults with a higher polygenic predisposition to major depressive disorders are more likely to be moderate to heavy smokers, implying that these adults may require targeted smoking cessation services.

Studying stimuli and smoking behaviors among self-identified gifted smokers and strategies for customizing cessation support

INTRODUCTION

The aim of the study was to examine smoking habits and triggers among self-identified gifted (inner experiences and awareness qualitatively different from the norm in terms of asynchronous development, advanced cognitive abilities, and heightened intensity) adults in order to customize smoking cessation support.

METHODS

A total of 123 participants were enrolled through Facility-Based and Snowball Sampling. Quantitative analysis focused on the relationship between overexcitabilities, nicotine dependence, motivation to quit, and smoking triggers, using the following questionnaires: the Overexcitability Questionnaire (OEQ-II) an indicator of areas of overexcitability, a heightened response and lowered threshold to stimuli; the Fagerström Test for Nicotine Dependence; a Cessation Motivation Questionnaire; and a Smoking Triggers Questionnaire. Qualitative analysis drew on six semi-structured interviews. Participant experiences of the relationship between smoking behaviors and experiences of multiple areas of overexcitability were analyzed using process coding.

RESULTS

The quantitative data indicate that self-identified gifted smokers who rate themselves as having 3–5 ‘High’ or ‘High Average’ overexcitabilities (OEs), are less likely to smoke in response to pattern, social, and addiction focused triggers than those self-reporting as having 0–2 OEs (Fisher’s exact test, p<0.1). In the interviews, we observed a high level of complexity in stimulation and smoking behavior, with all interviewees explicitly connecting their smoking habits with experiences of overexcitability. Two interviewees had given up smoking prior to the research and of the four who still smoked, three quit within a few days of the interview.

CONCLUSIONS

We found that psychometric testing and interviews designed to increase self-knowledge about the relationship between overexcitabilities and triggers for smoking have the potential to improve outcomes for smoking cessation among the gifted.

Adolescent cognitive function and incident early-onset type 2 diabetes

BACKGROUND

Cognitive function among apparently healthy adolescents has been associated with cardiovascular morbidity and mortality. We examined the relationship between global and subdomain cognitive scores in adolescence and early-onset type 2 diabetes (T2D) in men and women.

METHODS

A nationwide, population-based study of 971,677 Israeli born adolescents (56% men; mean age 17.4 years) who were medically examined and their cognitive performance was assessed before compulsory military service during 1992-2010. Data included global and subdomain cognitive Z-scores (problem-solving, verbal abstraction and categorization, verbal comprehension, and mathematical abilities). Data were linked to the Israeli National Diabetes Registry. The relations between global and subdomain scores and incident T2D was determined using Cox proportional hazard models and logistic regression models. Analyses were conducted separately for men and women.

FINDINGS

During 16,095,122 person-years, 3,570 individuals developed T2D. After adjustment, those in the low compared to the high quintile of global cognitive Z-score had the highest risk for T2D; HR 2.46, (95% CI 2.10-2.88) for men and 2.33 (95% CI 1.88-2.89) for women. A one-unit lower global cognitive Z-score was associated with 1.41 (95% CI 1.34-1.48) and 1.46 (95% CI 1.36-1.56) increased risks for men and women, respectively. The relationship was noted for the cognitive subdomains scores as well as for the global cognitive score, with no heterogeneity across cognitive subdomains.

INTERPRETATION

This large nationally representative cohort suggests relationship between global, as well as subdomain cognitive scores in late adolescence, and incident early onset T2D in both sexes, which was independent of socioeconomic status.

High IQ in Early Adulthood Is Associated with Parkinson's Disease

Background:

High education level and high occupational complexity have been implicated as risk factors for Parkinson’s disease (PD).

Objective:

The objective was to determine whether cognitive capacity, measured as IQ, in early adulthood is associated with the subsequent development of PD.

Method:

Data on IQ were retrieved from the Swedish Military Service Conscription Registry, comprising Swedish males who enlisted for military service in the period 1968–1993 (N = 1,319,235). After exclusion, 1,189,134 subjects in total were included in the present study. Individuals who later developed PD (N = 1,724) were identified using the Swedish National Patient Register and the Swedish Cause of Death Register.

Results:

High education level was associated with PD. High IQ was associated with PD (p < 0.0001), both when analyzed as a continuous variable and when divided into three categories. The hazard ratio for the high IQ category compared to the low IQ category was 1.35 (95% confidence interval 1.17–1.55). Strong test results on the subtests, measuring verbal, logic, visuospatial and technical abilities, were also associated with PD. In a subgroup, smoking was inversely associated with PD, as well as with IQ.

Conclusions:

This study identifies high IQ to be a risk factor for PD.

Intelligence, health and death

The field of cognitive epidemiology studies the prospective associations between cognitive abilities and health outcomes. We review research in this field over the past decade and describe how our understanding of the association between intelligence and all-cause mortality has consolidated with the appearance of new, population-scale data. To try to understand the association better, we discuss how intelligence relates to specific causes of death, diseases/diagnoses and biomarkers of health through the adult life course. We examine the extent to which mortality and health associations with intelligence might be attributable to people's differences in education, other indicators of socioeconomic status, health literacy and adult environments and behaviours. Finally, we discuss whether genetic data provide new tools to understand parts of the intelligence-health associations. Social epidemiologists, differential psychologists and behavioural and statistical geneticists, among others, contribute to cognitive epidemiology; advances will occur by building on a common cross-disciplinary knowledge base.

Do Financial Literacy and Financial Education Influence Smoking Behavior in the United States?

Smoking is still a serious economic, health, and social problem despite various efforts to curb its prevalence. We examined the influence of financial literacy and financial education on the smoking behavior in the United States in terms of the use of rational decision-making abilities to reduce irrational behavior. We hypothesized that financial literacy and financial education, as proxies for rational decision making, would reduce the likelihood of smoking. We used data from the Preference Parameters Study (PPS) of Osaka University conducted in the United States in 2010 and applied probit regression models to test our hypothesis on a sample of 3831 individuals. We found that financially literate people are less likely to be smokers, though we found no clear role of financial education in reducing the likelihood of smoking. Further, respondents' gender, age, unemployment status, and risky health behaviors such as drinking and gambling, have a significantly positive association with smoking, while marital status, university degree, family size, household income, household assets, physical exercise, and level of happiness have a significantly negative association. Our findings suggest that financial literacy, as an instrument encouraging rational decision making, could be a tool to help reduce smoking in the United States.

Decision making processes underlying avoidance of mandatory child vaccination in Croatia - a qualitative study

Despite extensive research evidencing child vaccination is safe and effective, we are witnessing a trend of increasing vaccine hesitancy which is listed among the top ten global health threats. Although some countries incorporate mandatory vaccination programs, no particularly efficient strategies for addressing vaccine avoidance have so far been identified. Within this study we investigated perceptions and reasoning of vaccine hesitant parents from Croatia where child vaccination is mandatory. The aims were to reveal different strategies by which they avoid mandatory vaccination schedules and hypothetical situations in which they would reconsider vaccinating, as well as to identify features of related decision-making. We conducted 25 semi-structured interviews with vaccine hesitant parents and analyzed the data using the framework of thematic analyses. The identified themes were related to the parents’ decision-making process, reflection as well as justification of their decision, avoidance behavior of mandatory vaccination schedules and related consequences, dealing with outcomes of the decision and reconsidering vaccinating. The results support and extend previous findings regarding vaccine reasoning, linking hesitancy with the experientially intuitive thinking style and social intuitionist model of moral reasoning. The findings provide important insights into vaccination avoidance and potential for reconsideration, as well as dealing with related risks. Furthermore, we offer a general framework as well as practical guidelines that may help the development of strategies aimed at increasing vaccination rates.

Genetic Contributions to Health Literacy

Higher health literacy is associated with higher cognitive function and better health. Despite its wide use in medical research, no study has investigated the genetic contributions to health literacy. Using 5783 English Longitudinal Study of Ageing (ELSA) participants (mean age = 65.49, SD = 9.55) who had genotyping data and had completed a health literacy test at wave 2 (2004-2005), we carried out a genome-wide association study (GWAS) of health literacy. We estimated the proportion of variance in health literacy explained by all common single nucleotide polymorphisms (SNPs). Polygenic profile scores were calculated using summary statistics from GWAS of 21 cognitive and health measures. Logistic regression was used to test whether polygenic scores for cognitive and health-related traits were associated with having adequate, compared to limited, health literacy. No SNPs achieved genome-wide significance for association with health literacy. The proportion of variance in health literacy accounted for by common SNPs was 8.5% (SE = 7.2%). Greater odds of having adequate health literacy were associated with a 1 standard deviation higher polygenic score for general cognitive ability [OR = 1.34, 95% CI (1.26, 1.42)], verbal-numerical reasoning [OR = 1.30, 95% CI (1.23, 1.39)], and years of schooling [OR = 1.29, 95% CI (1.21, 1.36)]. Reduced odds of having adequate health literacy were associated with higher polygenic profiles for poorer self-rated health [OR = 0.92, 95% CI (0.87, 0.98)] and schizophrenia [OR = 0.91, 95% CI (0.85, 0.96)). The well-documented associations between health literacy, cognitive function and health may partly be due to shared genetic etiology. Larger studies are required to obtain accurate estimates of SNP-based heritability and to discover specific health literacy-associated genetic variants.

Health literacy, cognitive ability and smoking: a cross-sectional analysis of the English Longitudinal Study of Ageing

OBJECTIVES

We used logistic regression to investigate whether health literacy and cognitive ability independently predicted whether participants have ever smoked and, in ever smokers, whether participants still smoked nowadays.

DESIGN

Cross-sectional study.

SETTING

This study used data from Wave 2 (2004-05) of the English Longitudinal Study of Ageing, which is a cohort study of adults who live in England and who, at baseline, were aged 50 years and older.

PARTICIPANTS

8734 (mean age=65.31 years, SD=10.18) English Longitudinal Study of Ageing participants who answered questions about their current and past smoking status, and completed cognitive ability and health literacy tests at Wave 2.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome measures were whether participants reported ever smoking at Wave 2 and whether ever smokers reported still smoking at Wave 2.

RESULTS

In models adjusting for age, sex, age left full-time education and occupational social class, limited health literacy (OR=1.096, 95% CI 0.988 to 1.216) and higher general cognitive ability (OR=1.000, 95% CI 0.945 to 1.057) were not associated with reporting ever smoking. In ever smokers, limited compared with adequate health literacy was associated with greater odds of being a current smoker (OR=1.194, 95% CI 1.034 to 1.378) and a 1 SD higher general cognitive ability score was associated with reduced odds of being a current smoker (OR=0.878, 95% CI 0.810 to 0.951), when adjusting for age, sex, age left full-time education and occupational social class.

CONCLUSIONS

When adjusting for education and occupation variables, this study found that health literacy and cognitive ability were independently associated with whether ever smokers continued to smoke nowadays, but not with whether participants had ever smoked.

The interplay between cognitive ability, alcohol consumption, and health characteristics

BACKGROUND

Higher cognitive ability is associated with favourable health characteristics. The relation between ability and alcohol consumption, and their interplay with other health characteristics, is unclear. We aimed to assess the relationship between cognitive ability and alcohol consumption and to assess whether alcohol consumption relates differently to health characteristics across strata of ability.

METHODS

For 63 120 Norwegian males, data on cognitive ability in early adulthood were linked to midlife data on alcohol consumption frequency (times per month, 0-30) and other health characteristics, including cardiovascular risk factors and mental distress. Relations were assessed using linear regression and reported as unstandardised beta coefficients [95% confidence interval (CI)].

RESULTS

The mean ± s.d. frequency of total alcohol consumption in the sample was 4.0 ± 3.8 times per month. In the low, medium, and high group of ability, the frequencies were 3.0 ± 3.3, 3.7 ± 3.5, and 4.7 ± 4.1, respectively. In the full sample, alcohol consumption was associated with physical activity, heart rate, fat mass, smoking, and mental distress. Most notably, each additional day of consumption was associated with a 0.54% (0.44-0.64) and 0.14% (0.09-0.18) increase in the probability of current smoking and mental distress, respectively. In each strata of ability (low, medium, high), estimates were 0.87% (0.57-1.17), 0.48% (0.31-0.66) and 0.49% (0.36-0.62) for current smoking, and 0.44% (0.28-0.60), 0.10% (0.02-0.18), and 0.09% (0.03-0.15) for mental distress, respectively.

CONCLUSIONS

Participants with low cognitive ability drink less frequently, but in this group, more frequent alcohol consumption is more strongly associated with adverse health characteristics.

Intelligence in youth and health behaviours in middle age

OBJECTIVE

We investigated the association between intelligence in youth and a range of health-related behaviours in middle age.

METHOD

Participants were the 5347 men and women who responded to the National Longitudinal Survey of Youth 1979 (NLSY-79) 2012 survey. IQ was recorded with the Armed Forces Qualification Test (AFQT) when participants were aged 15 to 23 years of age. Self-reports on exercise (moderate activity, vigorous activity, and strength training), dietary, smoking, drinking, and oral health behaviours were recorded when participants were in middle age (mean age = 51.7 years). A series of regression analyses tested for an association between IQ in youth and the different health related behaviours in middle age, while adjusting for childhood socio-economic status (SES) and adult SES.

RESULTS

Higher IQ in youth was significantly associated with the following behaviours that are beneficial to health: being more likely to be able to do moderate cardiovascular activity (Odds Ratio, 95% CI) (1.72, 1.35 to 2.20, p < .001) and strength training (1.61, 1.37 to 1.90, p < .001); being less likely to have had a sugary drink in the previous week (0.75, 0.71 to 0.80, p < .001); a lower likelihood of drinking alcohol heavily (0.67, 0.61 to 0.74, p < .001); being less likely to smoke (0.60, 0.56 to 0.65, p < .001); being more likely to floss (1.47, 1.35 to 1.59, p < .001); and being more likely to say they "often" read the nutritional information (1.20, 1.09 to 1.31, p < .001) and ingredients (1.24, 1.12 to 1.36, p < .001) on food packaging compared to always reading them. Higher IQ was also linked with dietary behaviours that may or may not be linked with poorer health outcomes (i.e. being more likely to have skipped a meal (1.10, 1.03 to 1.17, p = .005) and snacked between meals (1.37, 1.26 to 1.50, p < .001) in the previous week). An inverted u-shaped association was also found between IQ and the number of meals skipped per week. Higher IQ was also linked with behaviours that are known to be linked with poorer health (i.e. a higher likelihood of drinking alcohol compared to being abstinent from drinking alcohol (1.58, 1.47 to 1.69, p < .001)). A u-shaped association was found between IQ and the amount of alcohol consumed per week and an inverted u-shaped association was found between IQ and the number of cigarettes smoked a day. Across all outcomes, adjusting for childhood SES tended to attenuate the estimated effect size only slightly. Adjusting for adult SES led to more marked attenuation but statistical significance was maintained in most cases.

CONCLUSION

In the present study, a higher IQ in adolescence was associated with a number of healthier behaviours in middle age. In contrast to these results, a few associations were also identified between higher intelligence and behaviours that may or may not be linked with poor health (i.e. skipping meals and snacking between meals) and with behaviours that are known to be linked with poor health (i.e. drinking alcohol and the number of cigarettes smoked). To explore mechanisms of association, future studies could test for a range of health behaviours as potential mediators between IQ and morbidity or mortality in later life.

Cognitive performance in late adolescence and long-term risk of early heart failure in Swedish men

Aims

Heart failure (HF) incidence appears to increase among younger individuals, raising questions of how risk factors affect the younger population. We investigated the association of cognitive performance in late adolescence with long‐term risk of early HF.

Methods and results

We followed a cohort of Swedish men enrolled in mandatory military conscription in 1968–2005 (n = 1 225 300; mean age 18.3 years) until 2014 for HF hospitalization, using data from the Swedish National Inpatient Registry. Cognitive performance (IQ) was measured through a combination of tests, separately evaluating logical, verbal, visuospatial, and technical abilities. The results were standardized, weighted, and presented as stanines of IQ. The association between IQ and risk of HF was estimated using Cox proportional hazards models. In follow‐up, there were 7633 cases of a first HF hospitalization (mean age at diagnosis 50.1 years). We found an inverse relationship between global IQ and risk of HF hospitalization. Using the highest IQ stanine as reference, the adjusted hazard ratio for the lowest IQ with risk of HF was 3.11 (95% confidence interval 2.60–3.71), corresponding to a hazard ratio of 1.32 (95% CI 1.28–1.35) per standard deviation decrease of IQ. This association proved persistent across predefined categories of HF with respect to pre‐existing or concomitant co‐morbidities; it was less apparent among obese conscripts (P for interaction =0.0004).

Conclusion

In this study of young men, IQ was strongly associated with increased risk of early HF. The medical profession needs to be aware of this finding so as to not defer diagnosis.

Healthy cognitive ageing in the Lothian Birth Cohort studies: marginal gains not magic bullet

In the face of shifting demographics and an increase in human longevity, it is important to examine carefully what is known about cognitive ageing, and to identify and promote possibly malleable lifestyle and health-related factors that might mitigate age-associated cognitive decline. The Lothian Birth Cohorts of 1921 (LBC1921, n = 550) and 1936 (LBC1936, n = 1091) are longitudinal studies of cognitive and brain ageing based in Scotland. Childhood IQ data are available for these participants, who were recruited in later life and then followed up regularly. This overview summarises some of the main LBC findings to date, illustrating the possible genetic and environmental contributions to cognitive function (level and change) and brain imaging biomarkers in later life. Key associations include genetic variation, health and fitness, psychosocial and lifestyle factors, and aspects of the brain's structure. It addresses some key methodological issues such as confounding by early-life intelligence and social factors and emphasises areas requiring further investigation. Overall, the findings that have emerged from the LBC studies highlight that there are multiple correlates of cognitive ability level in later life, many of which have small effects, that there are as yet few reliable predictors of cognitive change, and that not all of the correlates have independent additive associations. The concept of marginal gains, whereby there might be a cumulative effect of small incremental improvements across a wide range of lifestyle and health-related factors, may offer a useful way to think about and promote a multivariate recipe for healthy cognitive and brain ageing.

Early life cognitive function and health behaviours in late childhood: testing the neuroselection hypothesis

Background

Higher cognitive function in childhood is associated with healthier behaviours and a reduced risk of chronic disease in adulthood, but it is unclear whether this selection of healthier behaviours occurs in childhood or later in life. The present study investigated how cognitive function at age 3–7 years was associated with health behaviours at age 11.

Methods

Verbal, non-verbal and spatial abilities were assessed using the British Ability Scales at ages 3–7. At age 11, children reported how often they engaged in sport/physical activity, sedentary behaviours (eg, reading and games console usage), cigarette smoking and alcohol consumption. Logistic regression was used to estimate odds of engaging in health behaviours at age 11 according to early life cognition.

Results

A 1 SD increase in early childhood verbal ability was associated with reduced odds of attempting smoking in boys and girls (OR 0.69 (95% CI 0.57 to 0.84)) and reduced odds of computer gaming in girls (OR 0.79 (95% CI 0.72 to 0.86)) by age 11. Early childhood verbal ability was also associated with reduced odds of regular participation in sport/active games (boys: OR 0.91 (95% CI 0.84 to 0.99); girls: OR 0.81 (95% CI 0.74 to 0.88)) and increased odds of reading for enjoyment (boys: OR 1.47 (95% CI 1.35 to 1.60); girls: OR 1.48 (95% CI 1.36 to 1.62)) at age 11. Early childhood non-verbal ability was associated with reduced odds of alcohol consumption in boys and girls (OR 0.92 (95% CI 0.85 to 0.99)) and reduced odds of online messaging in boys (OR 0.89 (95% CI 0.81 to 0.98)) at age 11. Early childhood spatial ability was associated with reduced odds of participating in sport/active games in boys at age 11 (OR 0.88 (95% CI 0.82 to 0.95).

Conclusion

Neuroselection may occur during early childhood resulting in some, but not all, healthier behaviours by age 11.

Childhood IQ and survival to 79: Follow-up of 94% of the Scottish Mental Survey 1947

OBJECTIVE

To extend previous literature that suggests higher IQ in youth is associated with living longer. Previous studies have been unable to assess reliably whether the effect differs across sexes and ages of death, and whether the effect is graded across different levels of IQ.

METHODS

We test IQ-survival associations in 94% of the near-entire population born in Scotland in 1936 who took an IQ test at age 11 (n = 70,805) and were traced in a 68-year follow-up.

RESULTS

Higher IQ at age 11 years was associated with a lower risk of death (HR = 0.80, 95% CI = 0.79, 0.81). The decline in risk across categories of IQ scores was graded across the full range with the effect slightly stronger in women (HR = 0.79, 95% CI = 0.77, 0.80) than in men (HR = 0.82, 95% CI = 0.81, 0.84). Higher IQ had a significantly stronger association with death before and including age 65 (HR = 0.76, 95% CI = 0.74, 0.77) than in those participants who died at an older age (HR = 0.79, 95% CI = 0.78, 0.80).

CONCLUSIONS

Higher childhood IQ is associated with lower risk of all-cause mortality in both men and women. This is the only near-entire population study to date that examines the association between childhood IQ and mortality across most of the human life course.

Childhood intelligence in relation to major causes of death in 68 year follow-up: prospective population study

Objectives To examine the association between intelligence measured in childhood and leading causes of death in men and women over the life course.Design Prospective cohort study based on a whole population of participants born in Scotland in 1936 and linked to mortality data across 68 years of follow-up.Setting Scotland.Participants 33 536 men and 32 229 women who were participants in the Scottish Mental Survey of 1947 (SMS1947) and who could be linked to cause of death data up to December 2015.Main outcome measures Cause specific mortality, including from coronary heart disease, stroke, specific cancer types, respiratory disease, digestive disease, external causes, and dementia.Results Childhood intelligence was inversely associated with all major causes of death. The age and sex adjusted hazard ratios (and 95% confidence intervals) per 1 SD (about 15 points) advantage in intelligence test score were strongest for respiratory disease (0.72, 0.70 to 0.74), coronary heart disease (0.75, 0.73 to 0.77), and stroke (0.76, 0.73 to 0.79). Other notable associations (all P<0.001) were observed for deaths from injury (0.81, 0.75 to 0.86), smoking related cancers (0.82, 0.80 to 0.84), digestive disease (0.82, 0.79 to 0.86), and dementia (0.84, 0.78 to 0.90). Weak associations were apparent for suicide (0.87, 0.74 to 1.02) and deaths from cancer not related to smoking (0.96, 0.93 to 1.00), and their confidence intervals included unity. There was a suggestion that childhood intelligence was somewhat more strongly related to coronary heart disease, smoking related cancers, respiratory disease, and dementia in women than men (P value for interactions <0.001, 0.02, <0.001, and 0.02, respectively).Childhood intelligence was related to selected cancer presentations, including lung (0.75, 0.72 to 0.77), stomach (0.77, 0.69 to 0.85), bladder (0.81, 0.71 to 0.91), oesophageal (0.85, 0.78 to 0.94), liver (0.85, 0.74 to 0.97), colorectal (0.89, 0.83 to 0.95), and haematopoietic (0.91, 0.83 to 0.98). Sensitivity analyses on a representative subsample of the cohort observed only small attenuation of the estimated effect of intelligence (by 10-26%) after adjustment for potential confounders, including three indicators of childhood socioeconomic status. In a replication sample from Scotland, in a similar birth year cohort and follow-up period, smoking and adult socioeconomic status partially attenuated (by 16-58%) the association of intelligence with outcome rates.Conclusions In a whole national population year of birth cohort followed over the life course from age 11 to age 79, higher scores on a well validated childhood intelligence test were associated with lower risk of mortality ascribed to coronary heart disease and stroke, cancers related to smoking (particularly lung and stomach), respiratory diseases, digestive diseases, injury, and dementia.

Childhood cognitive ability and smoking initiation, relapse and cessation throughout adulthood: evidence from two British cohort studies

AIMS

To test the relationship between early cognitive ability and major changes in smoking habits across adulthood, and test whether educational attainment mediates these associations.

DESIGN

Prospective observational study to examine the link between cognitive ability and smoking initiation, relapse and cessation at multiple time-points throughout adulthood in a pooled analysis of two cohorts.

SETTING

Great Britain 1981-2013.

PARTICIPANTS

A total of 16 653 participants from two British cohorts; 7191 from the 1970 British Cohort Study (BCS) and 9462 from the 1958 National Child Development Study (NCDS). Participants were 52.9% female and 27.3% were smokers, 24.8% were ex-smokers and 47.9% reported never smoking.

MEASUREMENTS

Cognitive ability was assessed at age 10 years in the BCS and 11 years in the NCDS. Outcomes were smoking initiation, relapse and cessation derived from changes in smoking status observed across five time-points between ages 26-42 in the BCS and six time-points between ages 23-55 in the NCDS. Educational attainment was examined as a mediating variable. Controls were age, gender, social class, self-control, psychological distress, parental smoking and a study indicator (BCS/NCDS).

FINDINGS

In adjusted regression models, a 1 standard deviation increase in cognitive ability predicted a 0.5 percentage point (95% CI = -0.9 to -0.1) reduced probability of smoking and a 2.9 percentage point (95% CI = 2.1-3.7) higher probability of smoking cessation throughout adulthood, but did not change the likelihood of smoking relapse significantly. Differences in educational attainment explained approximately half the association between childhood cognitive ability and smoking initiation/cessation.

CONCLUSIONS

Lower cognitive ability, measured in childhood before smoking is initiated, appears to predict a higher likelihood of taking up smoking and a lower likelihood of quitting in adulthood. Educational attainment appears to mediate this effect: children with higher cognitive ability tend to become more highly educated adults which, in turn, predicts lower rates of smoking initiation and increased rates of smoking cessation.

GWAS meta-analysis reveals novel loci and genetic correlates for general cognitive function: a report from the COGENT consortium

The complex nature of human cognition has resulted in cognitive genomics lagging behind many other fields in terms of gene discovery using genome-wide association study (GWAS) methods. In an attempt to overcome these barriers, the current study utilized GWAS meta-analysis to examine the association of common genetic variation (~8M single-nucleotide polymorphisms (SNP) with minor allele frequency ⩾1%) to general cognitive function in a sample of 35 298 healthy individuals of European ancestry across 24 cohorts in the Cognitive Genomics Consortium (COGENT). In addition, we utilized individual SNP lookups and polygenic score analyses to identify genetic overlap with other relevant neurobehavioral phenotypes. Our primary GWAS meta-analysis identified two novel SNP loci (top SNPs: rs76114856 in the CENPO gene on chromosome 2 and rs6669072 near LOC105378853 on chromosome 1) associated with cognitive performance at the genome-wide significance level (P<5 × 10^-8). Gene-based analysis identified an additional three Bonferroni-corrected significant loci at chromosomes 17q21.31, 17p13.1 and 1p13.3. Altogether, common variation across the genome resulted in a conservatively estimated SNP heritability of 21.5% (s.e.=0.01%) for general cognitive function. Integration with prior GWAS of cognitive performance and educational attainment yielded several additional significant loci. Finally, we found robust polygenic correlations between cognitive performance and educational attainment, several psychiatric disorders, birth length/weight and smoking behavior, as well as a novel genetic association to the personality trait of openness. These data provide new insight into the genetics of neurocognitive function with relevance to understanding the pathophysiology of neuropsychiatric illness.

Childhood academic ability in relation to cigarette, alcohol and cannabis use from adolescence into early adulthood: Longitudinal Study of Young People in England (LSYPE)

OBJECTIVES

Our aim was to determine the association between childhood academic ability and the onset and persistence of tobacco, alcohol and cannabis use across adolescence in a representative sample of English schools pupils. Previous research has produced conflicting findings.

DESIGN

Data from 7 years of the Longitudinal Study of Young People in England (LSYPE), 2004-2010 (age 13/14-19/20).

SETTING

Self-completion questionnaires during home visits, face-to-face interviews and web-based questionnaires.

PARTICIPANTS

Data from 6059 participants (3093 females) with information on academic ability around age 11 and health behaviours from age 13/14 to 16/17 (early adolescence) and from age 18/19 to 19/20 (late adolescence).

OUTCOME MEASURES

Regularity of cigarette smoking, alcohol drinking and cannabis use from early to late adolescence.

RESULTS

In multinomial logistic regression models adjusting for a range of covariates, the high (vs low) academic ability reduced the risk of persistent cigarette smoking (RR=0.62; CI 95% 0.48 to 0.81) in early adolescence. High (vs low) academic ability increased the risk of occasional (RR=1.25; CI 95% 1.04 to 1.51) and persistent (RR=1.83; CI 95% 1.50 to 2.23) regular alcohol drinking in early adolescence and persistent (RR=2.28; CI 95% 1.84 to 2.82) but not occasional regular alcohol drinking in late adolescence. High (vs low) academic ability was also positively associated with occasional (RR=1.50; CI 95% 1.22 to 1.83) and persistent (RR=1.91; CI 95% 1.57 to 2.34) cannabis use in late adolescence.

CONCLUSIONS

In a sample of over 6000 young people in England, high childhood academic at age 11 is associated with a reduced risk of cigarette smoking but an increased risk of drinking alcohol regularly and cannabis use. These associations persist into early adulthood, providing evidence against the hypothesis that high academic ability is associated with temporary 'experimentation' with substance use.

Young adulthood cognitive ability predicts statin adherence in middle-aged men after first myocardial infarction: A Swedish National Registry study

Background

Cognitive ability (CA) is positively related to later health, health literacy, health behaviours and longevity. Accordingly, a lower CA is expected to be associated with poorer adherence to medication. We investigated the long-term role of CA in adherence to prescribed statins in male patients after a first myocardial infarction (MI).

Methods

CA was estimated at 18–20 years of age from Military Conscript Register data for first MI male patients (≤60 years) and was related to the one- and two-year post-MI statin adherence on average 30 years later. Background and clinical data were retrieved through register linkage with the unselected national quality register SWEDEHEART for acute coronary events (Register of Information and Knowledge about Swedish Heart Intensive Care Admissions) and secondary prevention (Secondary Prevention after Heart Intensive Care Admission). Previous and present statin prescription data were obtained from the Prescribed Drug Register and adherence was calculated as ≥80% of prescribed dispensations assuming standard dosage. Logistic regression was used to estimate crude and adjusted associations. The primary analyses used 2613 complete cases and imputing incomplete cases rendered a sample of 4061 cases for use in secondary (replicated) analyses.

Results

One standard deviation increase in CA was positively associated with both one-year (OR 1.15 (CI 1.01–1.31), P < 0.05) and two-year (OR 1.14 (CI 1.02–1.27), P < 0.05) adherence to prescribed statins. Only smoking attenuated the CA–adherence association after adjustment for a range of > 20 covariates. Imputed and complete case analyses yielded very similar results.

Conclusions

CA estimated on average 30 years earlier in young adulthood is a risk indicator for statin adherence in first MI male patients aged ≤60 years. Future research should include older and female patients and more socioeconomic variables.

Reaction Time Explains IQ's Association with Death

Lower IQ is associated with earlier death, but the cause of the relationship is unknown. In the present study, psychometric intelligence and reaction times were both significantly related to all-cause mortality in a representative sample of 898 people aged 56 years who were followed up with respect to survival until age 70. The association between IQ and mortality remained significant after adjusting for education, occupational social class, and smoking, all of which have been hypothesized as confounding variables. The effect of IQ on mortality was not significant after adjusting for reaction time, suggesting that reduced efficiency of information processing might link lower mental ability and earlier death. This new field of cognitive epidemiology provides arguably the strongest evidence for the importance of psychological factors in physical health and human survival. Finding the mechanisms that relate psychometric intelligence to mortality might help in formulating effective interventions to reduce inequalities in health.

Intelligence Predicts Health and Longevity, but Why?

Large epidemiological studies of almost an entire population in Scotland have found that intelligence (as measured by an IQ-type test) in childhood predicts substantial differences in adult morbidity and mortality, including deaths from cancers and cardiovascular diseases. These relations remain significant after controlling for socioeconomic variables. One possible, partial explanation of these results is that intelligence enhances individuals' care of their own health because it represents learning, reasoning, and problem-solving skills useful in preventing chronic disease and accidental injury and in adhering to complex treatment regimens.

Adolescent Self-Organization and Adult Smoking and Drinking over Fifty Years of Follow-Up: The British 1946 Birth Cohort

Variations in markers of adolescent self-organization predict a range of economic and health-related outcomes in general population studies. Using a population-based birth cohort study we investigated associations between adolescent self-organization and two common factors over adulthood influencing health, smoking and alcohol consumption. The MRC National Survey of Health and Development (the British 1946 birth cohort) was used to test associations between a dimensional measure of adolescent self-organization derived from teacher ratings, and summary longitudinal measures of smoking and alcohol consumption over the ensuing five decades. Multinomial regression models were adjusted for sex, adolescent emotional and conduct problems, occupational social class of origin, childhood cognition, educational attainment and adult occupational social class. With all covariates adjusted, higher adolescent self-organization was associated with fewer smoking pack years, although not with quitting; there was no association with alcohol consumption across adulthood (none or heavy compared with light to moderate). Adolescent self-organization appears to be protective against smoking, but not against heavy alcohol consumption. Interpretation of this differential effect should be embedded in an understanding of the social and sociodemographic context in which these health behaviours occur over time.

After 50 years and 200 papers, what can the Midspan cohort studies tell us about our mortality?

OBJECTIVE

To distil the main findings from published papers on mortality in three cohorts involving over 27,000 adults, recruited in Scotland between 1965 and 1976 and followed up ever since.

METHOD

We read and summarized 48 peer-reviewed papers about all-cause and cause-specific mortality in these cohorts, published between 1978 and 2013.

RESULTS

Mortality rates were substantially higher among cigarette smokers in all social classes and both genders. Exposure to second-hand smoke was also damaging. Exposure to higher levels of black smoke pollution was associated with higher mortality. After smoking, diminished lung function was the risk factor most strongly related to higher mortality, even among never-smokers. On average, female mortality rates were much lower than male but the same risk factors were predictors of mortality. Mortality rates were highest among men whose paternal, own first and most recent jobs were manual. Specific causes of death were associated with different life stages. Upward and downward social mobility conferred intermediate mortality rates. Low childhood cognitive ability was strongly associated with low social class in adulthood and higher mortality before age 65 years. There was no evidence that daily stress contributed to higher mortality among people in lower social positions. Men in manual occupations with fathers in manual occupations, who smoked and drank >14 units of alcohol a week had cardiovascular disease mortality rates 4.5 times higher than non-manual men with non-manual fathers, who neither smoked nor drank >14 units. Men who were obese and drank >14 units of alcohol per day had a mortality rate due to liver disease 19 times that of normal or underweight non-drinkers. Among women who never smoked, mortality rates were highest in severely obese women in the lowest occupational classes.

CONCLUSION

These studies highlight the cumulative effect of adverse exposures throughout life, the complex interplay between social circumstances, culture and individual capabilities, and the damaging effects of smoking, air pollution, alcohol and obesity.

Intelligence and Disability Pension in Swedish Men and Women Followed from Childhood to Late Middle Age

OBJECTIVE

To investigate the association between intelligence and disability pension due to mental, musculoskeletal, cardiovascular, and substance-use disorders among men and women, and to assess the role of childhood social factors and adulthood work characteristics.

METHODS

Two random samples of men and women born 1948 and 1953 (n = 10 563 and 9 434), and tested for general intelligence at age 13, were followed in registers for disability pension until 2009. Physical and psychological strains in adulthood were assessed using job exposure matrices. Associations were examined using Cox proportional hazard regression models, with increases in rates reported as hazard ratios (HRs) with 95% confidence intervals (95%CI) per decrease in stanine intelligence.

RESULTS

In both men and women increased risks were found for disability pension due to all causes, musculoskeletal disorder, mental disorder other than substance use, and cardiovascular disease as intelligence decreased. Increased risk was also found for substance use disorder in men. In multivariate models, HRs were attenuated after controlling for pre-school plans in adolescence, and low job control and high physical strain in adulthood. In the fully adjusted model, increased HRs remained for all causes (male HR 1.11, 95%CI 1.07-1.15, female HR 1.06, 95%CI 1.02-1.09) and musculoskeletal disorder (male HR 1.16, 95%CI 1.09-1.24, female HR 1.08, 95%CI 1.03-1.14) during 1986 to 2009.

CONCLUSION

Relatively low childhood intelligence is associated with increased risk of disability pension due to musculoskeletal disorder in both men and women, even after adjustment for risk factors for disability pension measured over the life course.

Childhood cognitive ability moderates later-life manifestation of type 2 diabetes genetic risk

Objective: The study investigated whether childhood cognitive ability moderates Type 2 diabetes polygenic risk manifestation in older age. Method: In 940 relatively healthy people (mean age 69.55 ± 0.85), we tested whether self-reported diabetes and hemoglobin HbA1c (HbA1c) levels were predicted by diabetes polygenic risk, cognitive ability measured about 60 years earlier, and their interaction. Polygenic risk scores aggregated the small effects of up to nearly 121,000 single-nucleotide polymorphisms (SNPs). Participants’ cognitive ability was measured at age 11. Results: Both polygenic risk and low childhood cognitive ability significantly predicted diabetes diagnosis. Polygenic risk interacted with cognitive ability (p = .02), predicting HbA1c levels more strongly in people with below-median cognitive ability (effect r = .21) than in people with above-median cognitive ability (effect r = .10). The interaction term was not significant for self-reported diabetes (p = .34), although the genetic risk-diabetes association showed a tendency of being stronger among those with below-median cognitive ability. Conclusions: Higher premorbid cognitive ability may provide some environmental protection against the manifestation of Type 2 diabetes genetic risk. This information may improve early identification of diabetes risk and inform intervention development.

Does high intelligence improve prognosis? The association of intelligence with recurrence and mortality among Swedish men with coronary heart disease

BACKGROUND

Lower intelligence early in life is associated with increased risks for coronary heart disease (CHD) and mortality. Intelligence level might affect compliance to treatment but its prognostic importance in patients with CHD is unknown.

METHODS

A cohort of 1923 Swedish men with a measure of intelligence from mandatory military conscription in 1969-1970 at age 18-20, who were diagnosed with CHD 1991-2007, were followed to the end of 2008.

PRIMARY OUTCOME

recurrent CHD event. Secondary outcome: case fatality from the first event, cardiovascular and all-cause mortality. National registers provided information on CHD events, comorbidity, mortality and socioeconomic factors.

RESULTS

The fully adjusted HRs for recurrent CHD for medium and low intelligence, compared with high intelligence, were 0.98, (95% CIs 0.83 to 1.16) and 1.09 (0.89 to 1.34), respectively. The risks were increased for cardiovascular and all-cause mortality with lower intelligence, but were attenuated in the fully adjusted models (fully adjusted HRs for cardiovascular mortality 1.92 (0.94 to 3.94) and 1.98 (0.89 to 4.37), respectively; for all-cause mortality 1.63 (1.00 to 2.65) and 1.62 (0.94 to 2.78), respectively). There was no increased risk for case-fatality at the first event (fully adjusted ORs 1.06 (0.73 to 1.55) and 0.97 (0.62 to 1.50), respectively).

CONCLUSIONS

Although we found lower intelligence to be associated with increased mortality in middle-aged men with CHD, there was no evidence for its possible effect on recurrence in CHD.

Occupational complexity and lifetime cognitive abilities

Objective:

To examine associations between complexity of main lifetime occupation and cognitive performance in later life.

Methods:

Occupational complexity ratings for data, people, and things were collected from the Dictionary of Occupational Titles for 1,066 individuals (men = 534, women = 532) in the Lothian Birth Cohort 1936. IQ data were available from mean age 11 years. Cognitive ability data across the domains of general ability, processing speed, and memory were available at mean age 70 years.

Results:

General linear model analyses indicated that complexity of work with people and data were associated with better cognitive performance at age 70, after including age 11 IQ, years of education, and social deprivation.

Conclusions:

The current findings are supportive of the differential preservation hypotheses that more stimulating environments preserve cognitive ability in later life, although the continued effects into old age are still debated. Studies that have early-life cognitive ability measures are rare, and the current study offers interesting prospects for future research that may further the understanding of successful aging.

Do dietary patterns influence cognitive function in old age?

BACKGROUND

Evidence from observational studies to date suggests that healthy dietary patterns are associated with better cognitive performance in later life. We examined the extent to which childhood intelligence quotient (IQ) and socioeconomic status account for this association.

METHODS

Analyses were carried out on 882 participants in the Lothian Birth Cohort 1936 Study. Four dietary patterns were extracted using principal components analysis of a food frequency questionnaire, namely "Mediterranean-style," "health aware," "traditional," and "sweet foods." Cognitive function was assessed at the age of 70 years, including general (g) cognitive ability, processing speed, memory, and verbal ability.

RESULTS

Before adjustment for childhood IQ and socioeconomic status, the "Mediterranean-style" dietary pattern was associated with significantly better cognitive performance (effect size as partial eta-square (ηp(2)) range = 0.005 to 0.055), and the "traditional" dietary pattern was associated with poorer performance on all cognitive domains measured in old age (ηp(2) = 0.009 to 0.103). After adjustment for childhood IQ (measured at the age of 11 years) and socioeconomic status, statistical significance was lost for most associations, with the exception of verbal ability and the "Mediterranean-style" pattern (National Adult Reading Test (NART) ηp(2) = 0.006 and Wechsler Test of Adult Reading (WTAR) ηp(2) = 0.013), and the "traditional" pattern (NART ηp(2) = 0.035 and WTAR ηp(2) = 0.027).

CONCLUSIONS

Our results suggest a pattern of reverse causation or confounding; a higher childhood cognitive ability (and adult socioeconomic status) predicts adherence to a "healthy" diet and better cognitive performance in old age. Our models show no direct link between diet and cognitive performance in old age; instead they are related via the lifelong-stable trait of intelligence.

Cognitive ability in early adulthood as a predictor of habitual drug use during later military service and civilian life: the Vietnam Experience Study

BACKGROUND

Recent reports have linked cognitive ability (IQ) with alcohol dependency, but the relationship with illegal drug use is not well understood.

METHODS

Participants were 14,362 male US Vietnam veterans with IQ test results at entry into military service in 1965-1971 (mean age 22.58) who participated in a telephone interview in 1985-1986. A structured diagnostic telephone interview was used to ascertain habitual drug use during military service (for once a week, ≥ 3 months) and in civilian life (in the past 12 months, ≥ once a week), combat exposure, and post-traumatic stress disorder according to established Diagnostic and Statistical Manual of Mental disorders criteria (version III).

RESULTS

In unadjusted analysis, men with high IQ scores were less likely to be habitual users of cannabis (OR=0.89, 95% CI=0.86, 0.93), cocaine (OR=0.69, 95% CI=0.61, 0.78), heroin (OR=0.80, 95% CI=0.73, 0.88), amphetamines (OR=0.90, 95% CI=0.83, 0.98), barbiturates (OR=0.79, 95% CI=0.72, 0.86) and LSD (OR=0.91, 95% CI=0.82, 0.99) during military service and civilian life. These associations were markedly attenuated after adjustment for socioeconomic status in early and later civilian life.

CONCLUSION

In this cohort, socioeconomic position might lie on the pathway linking earlier IQ and later habitual drug use but might also act as a surrogate for IQ. This suggests interventions to prevent drug use could attempt to improve early life IQ and opportunities for employment.

Smoking, childhood IQ, and cognitive function in old age

OBJECTIVES

To examine the association between smoking history and cognitive function in old age, and whether it remains after controlling for childhood cognitive ability (IQ) and adult socioeconomic status (SES).

METHODS

In the Lothian Birth Cohort 1936 Study, 1080 men and women, who previously participated in a nationwide IQ-type test in childhood, were followed up at age 70. The associations between smoking history and age 70 IQ, general cognitive ability (g), processing speed, memory, and verbal ability were assessed.

RESULTS

Lower childhood IQ was associated with a higher risk of becoming a smoker and continuing to smoke in late life, and with reduced lung function (FEV1) in late life. Current smokers scored significantly lower than ex-smokers and never smokers on tests of age 70 IQ, general cognitive ability, and processing speed, but not memory or verbal ability. After controlling for childhood IQ and SES, current smoking at age 70 (but not pack years of smoking) was associated with impairments in general cognitive ability and processing speed.

CONCLUSION

Smoking in old age makes a small, independent contribution to cognitive performance in old age.

Pre- and postnatal drivers of childhood intelligence: evidence from Singapore

This study seeks to investigate what influences intelligence in early childhood. The Singapore Cohort Study of the Risk Factors of Myopia (SCORM) is used to assess determinants of childhood IQ and changes in IQ. This longitudinal data set, collected in 1999, includes a wealth of demographic, socioeconomic and prenatal characteristics. The richness of the data allows various econometric approaches to be employed, including the use of ordered and multinomial logit analysis. Mother's education is found to be a consistent and key determinant of childhood IQ. Father's education and school quality are found to be key drivers for increasing IQ levels above the average sample movement.

Intelligence quotient (IQ) in adolescence and later risk of alcohol-related hospital admissions and deaths--37-year follow-up of Swedish conscripts

AIMS

To investigate the relationship between intelligence measured at ages 18-19 and later alcohol-related hospital admission and mortality among men, while controlling for possible confounders.

DESIGN

Cohort study.

SETTING AND PARTICIPANTS

A total of 49,321 Swedish men who were conscripted for military training in 1969-70 and followed until 2007.

MEASUREMENTS

Intelligence quotient (IQ) measured at conscription is the exposure, while alcohol-related hospital admission and death are the two outcomes. Adjustments for following variables were made: early life circumstances [childhood socio-economic position (SEP), father's drinking], mental health, social adjustment and behavioural factors measured at age 18 (psychiatric diagnosis, contact with police and child care, low emotional control, daily smoking, risky use of alcohol) and adult social position (attained education, SEP and income at age 40).

FINDINGS

IQ had an inverse and graded association with later alcohol-related problems. For alcohol-related hospital admissions the crude hazard ratio (HR) was 1.29 (95% CI = 1.26-1.31) and for alcohol-related mortality it was 1.21 (95% CI = 1.17-1.24) for every one point decrease on the nine-point IQ scale. Adjustment for risk factors measured at age 18 attenuated the association somewhat for both outcomes. After adjustment for social position as adult, the HR was considerably lower resulting in a HR of 1.06 (95% CI = 1.02-1.10) for alcohol-related hospital admissions and 1.01 (95% CI = 0.95-1.08) for alcohol-related mortality.

CONCLUSIONS

In Swedish men there is an association between IQ in early adulthood and later alcohol-related hospital admission and death. Social position as adult could be an important contributory factor.

Adolescent IQ and survival in the Wisconsin longitudinal study

OBJECTIVE

This study attempts to explain the ubiquitous positive correlation between cognitive ability (IQ) and survival.

METHODS

A sample of 10,317 Wisconsin high school graduates of 1957 was followed until 2009, from ages 18 to 68 years. Mortality was analyzed using a Weibull survival model that includes gender, social background, Henmon-Nelson IQ, and rank in high school class.

RESULTS

Rank in high school class, a cumulative measure of responsible performance during high school, entirely mediates the relationship between adolescent IQ and survival. Its effect on survival is 3 times greater than that of IQ, and it accounts for about 10% of the female advantage in survival.

DISCUSSION

Cognitive functioning may improve survival by promoting responsible and timely patterns of behavior that are firmly in place by late adolescence. Prior research suggests that conscientiousness, one of the "Big Five" personality characteristics, plays a key role in this relationship.

Genetics of the association between intelligence and nicotine dependence: a study of male Swedish twins

AIMS

Previous studies have found inverse associations between intelligence quotient (IQ) and cigarette smoking, but the causal pathways linking IQ with smoking status and nicotine dependence (ND) are not well understood. The aim of this study was to explore the associations between IQ and ND using a genetically informative twin design to detect whether any association is because of shared genetic or environmental factors.

DESIGN

A population-based twin cohort with IQ measured in adolescence and ND later in life, analysed by classical twin modeling based on linear structural equations.

SETTING

Swedish national registry data.

PARTICIPANTS

A total of 5040 male twins born 1951-84.

MEASUREMENTS

IQ was measured at military conscription at a mean age of 18 years. ND was self-reported at the ages of 22-57 years using the Fagerström Test for ND scale (FTND). Both cigarette smoking and Swedish snus use were analysed.

FINDINGS

Both IQ and ND showed moderate heritability (0.58 and 0.39, respectively). The heritability of ND was similar for cigarette smoking and snus use. The phenotypic correlation between IQ and ND was weak: -0.11 (-0.16, -0.06) for total ND. Bivariate analysis revealed that this correlation was mainly because of genetic factors, but still the genetic correlation between IQ and ND from cigarette smoking was only -0.24.

CONCLUSIONS

Nicotine dependence, as measured by the Fagerström Test for Nicotine Dependence, shows moderate heritability in both smokers and snus users but is only weakly associated with intelligence quotient; common genetic factors underlying nicotine dependence and intelligence quotient probably account for little of the observed association between smoking and intelligence quotient.

Associations between self-assessed masticatory ability and higher brain function among the elderly

Among the elderly, the quality of higher brain function is a contributing factor in performing activities of daily living. The aim of the study is to elucidate, epidemiologically, associations between mastication and higher brain function. A total of 208 community-dwelling elderly persons, aged 70-74 years, were enrolled. Self-assessed masticatory ability (masticatory ability) was classified into one of three categories: ability to chew all kinds of food, ability to chew only slightly hard food, or ability to chew only soft or pureed food. Brain function was assessed by four neuropsychological tests: Raven's Colored Progressive Matrices (RCPM) test, the Verbal Paired Associates 1 (VerPA) task and the Visual Paired Associates 1 task (from the Wechsler Memory Scale Revised Edition), and the Block Design subtest (from the Wechsler Adult Intelligence Scales-Third Edition). Correlations between masticatory ability and each test were examined using Spearman rank correlation coefficients. Multinominal logistic regression models were conducted with the neuropsychological tests as the dependent variables and masticatory ability as the principal independent variable to adjust for age, gender, educational background, social activity, drinking/smoking habits, chronic medical conditions and dental status. Significant correlations were found between the RCPM test, the VerPA task, the Block Design test and masticatory ability. In multinominal logistic regression models, poor masticatory ability was significantly and independently related to the categories under the mean-s.d. points compared with those of the mean ± s.d. ranges for RCPM test and the VerPA task. Significant associations may exist between mastication and higher brain function among the elderly.

Childhood IQ and all-cause mortality before and after age 65: Prospective observational study linking the Scottish Mental Survey 1932 and the Midspan studies

OBJECTIVES

The objective was to investigate how childhood IQ related to all-cause mortality before and after age 65.

DESIGN

The Midspan prospective cohort studies, followed-up for mortality for 25 years, were linked to individuals' childhood IQ from the Scottish Mental Survey 1932.

METHODS

The Midspan studies collected data on risk factors for cardiorespiratory disease from a questionnaire and at a screening examination, and were conducted on adults in Scotland in the 1970s. An age 11 IQ from the Scottish Mental Survey 1932, a cognitive ability test conducted on 1921-born children attending schools in Scotland, was found for 938 Midspan participants. The relationship between childhood IQ and mortality risk, adjusting for adulthood socio-economic confounders, was analysed. The effect of adjustment for childhood IQ on the relationship between established risk factors (blood pressure, smoking, height and respiratory function) and mortality was also investigated.

RESULTS

For deaths occurring up to age 65, there was a 36% increased risk per standard deviation decrease (15 points) in childhood IQ which was reduced to 29% after adjusting for social class and deprivation category. There was no statistically significant relationship between childhood IQ and deaths occurring after the age of 65. Adjustment for childhood IQ attenuated the risk factor-mortality relationship in deaths occurring up to age 65, but had no effect in deaths occurring after age 65.

CONCLUSIONS

Childhood IQ was significantly related to deaths occurring up to age 65, but not to deaths occurring after age 65.

Childhood IQ and social factors on smoking behaviour, lung function and smoking-related outcomes in adulthood: Linking the Scottish Mental Survey 1932 and the Midspan studies

OBJECTIVE

To investigate the associations of childhood IQ and adult social factors, and smoking behaviour, lung function (forced expiratory volume in one second; FEV(1)), and smoking-related outcomes in adulthood.

DESIGN

Retrospective cohort study.

METHOD

Participants were from the Midspan prospective studies conducted on Scottish adults in the 1970s. The sample consisted of 938 Midspan participants born in 1921 who were successfully matched with their cognitive ability test results on the Scottish Mental Survey 1932.

RESULTS

Structural equation modelling showed that age 11 IQ was not directly associated with smoking consumption, but that IQ and adult social class had indirect effects on smoking consumption via deprivation category. The influence of IQ on FEV(1) was partly indirect via social class. Gender influenced smoking consumption and also IQ and social class. There was a 21% higher risk of having a smoking-related hospital admission, cancer, or death during 25 years of follow-up for each standard deviation disadvantage in IQ. Adjustment for adult social class, deprivation category, and smoking reduced the association to 10%.

CONCLUSION

Childhood IQ was associated with social factors which influenced lung function in adulthood, but was not associated directly with smoking consumption. In future studies, it is important to consider other pathways which may account for variance in the link between childhood IQ and health in later life.

Intelligence in relation to obesity: a systematic review and meta-analysis

We performed a systematic review describing obesity/intelligent quotient (IQ) association, particularly childhood IQ in relation to adulthood obesity. After screening 883 citations from five electronic databases, we included 26 studies, most of medium quality. The weighted mean difference (WMD) of the full IQ (FIQ)/obesity association in the pre-school children was -15.1 (P > 0.05). Compared with controls, the WMD of FIQ and performance IQ of obese children were -2.8 and -10.0, respectively (P < 0.05), and the WMD of verbal IQ was -7.01 (P > 0.05). With increasing obesity, the FIQ in pre-school children declined, with a significant difference for severely obese children and FIQ. In pubertal children, a slightly different effect of FIQ and obesity emerged. Two studies reported an inverse FIQ/obesity association in adults, but it was non-significant after adjusting for educational attainment. Four papers found that childhood FIQ was inversely associated with adult body mass index, but after adjusting for education, became null. Overall there was an inverse FIQ/obesity association, except in pre-school children. However, after adjusting for educational attainment, FIQ/obesity association was not significantly different. A lower FIQ in childhood was associated with obesity in later adulthood perhaps with educational level mediating the persistence of obesity in later life.

Executive function and survival in the context of chronic illness

BACKGROUND

Individual differences in executive function (EF) have been shown to predict risk factors for chronic illness. It is not currently known whether EFs also predict survival time following a diagnosis of a chronic illness.

PURPOSE

The objective of this investigation was to examine the association between individual differences in EF and survival time among individuals suffering from one or more chronic illness.

METHODS

A sample of 162 community-dwelling older adults who suffered from a chronic illness at baseline underwent thorough medical and neurological examinations to ensure freedom from actual or probable dementia. Participants completed cognitive testing and were subsequently followed for 10 years; survival was assessed as survival time over the follow-up interval.

RESULTS

Findings indicated that individual differences in EF predicted survival time, and this association held when adjustments were made for demographic variables (age, sex), education, and body mass index.

CONCLUSION

Individual differences in EF may be important determinants of survival in the context of chronic illness.