Reaction time and incident cancer: 25 years of follow-up of study members in the UK Health and Lifestyle Survey.

OBJECTIVES: To investigate the association of reaction time with cancer incidence. METHODS: 6900 individuals aged 18 to 94 years who participated in the UK Health and Lifestyle Survey in 1984/1985 and were followed for a cancer registration for 25 years. RESULTS: Disease surveillance gave rise to 1015 cancer events from all sites. In general, there was essentially no clear pattern of association for either simple or choice reaction time with cancer of all sites combined, nor specific malignancies. However, selected associations were found for lung cancer, colorectal cancer and skin cancer. CONCLUSIONS: In the present study, reaction time and its components were not generally related to cancer risk.

IQ in childhood and atherosclerosis in middle-age: 40 Year follow-up of the Newcastle Thousand Families Cohort Study.

OBJECTIVE: Carotid intima-media thickness (IMT) is a known precursor to coronary heart disease (CHD) and other relevant health outcomes such as stroke and cognitive impairment. In addition, higher childhood intelligence has been associated with lower risk of coronary heart disease events in later life, although the mechanisms of effect are unclear. We therefore examined the association between childhood intelligence and atherosclerosis using carotid IMT as a marker of the atherosclerotic process. APPROACH: Participants were 412 members of the Newcastle Thousand Families Study, a prospective cohort study of all 1142 births in the city of Newcastle in May and June 1947, who took an IQ test and English and arithmetic tests at age 11 years. Study members participated in a medical examination and lifestyle assessment at age 49-51 years during which IMT was measured using ultrasound techniques. RESULTS: Individuals with higher childhood IQ score had a lower mean IMT in middle-age. A standard deviation higher score in childhood overall IQ was associated with a 0.053 mm (95% CI -0.102, -0.004) lower IMT in men and a 0.039 mm (95% CI -0.080, -0.002) lower IMT in women. Similar levels of association were found for the English and arithmetic tests. After adjustment for a range of covariates including education, the size of effect was undiminished in men but increased in women. CONCLUSIONS: In the present study, higher childhood IQ scores were associated with a lower degree of atherosclerosis by middle-age.

Neuroticism combined with slower and more variable reaction time: synergistic risk factors for 7-year cognitive decline in females.

OBJECTIVE: Among adults, slower and more variable reaction times are associated with worse cognitive function and increased mortality risk. Therefore, it is important to elucidate risk factors for reaction time change over the life course. Method. Data from the Health and Lifestyle Survey (HALS) were used to examine predictors of 7-year decline in reaction time (N = 4,260). Regression-derived factor scores were used to summarize general change across 4 reaction time variables: simple mean, 4-choice mean, simple variability, and 4-choice variability (53.52% of variance). RESULTS: Age (B = .02, p < .001) and HALS1 baseline reaction time (B = -.10, p = .001) were significant risk factors for males (N = 1,899). In addition to these variables, in females (N = 2,361), neuroticism was significant and interacted synergistically with baseline reaction time (B = .06, p = .04). Adjustment for physiological variables explained the interaction with neuroticism, suggesting that candidate mechanisms had been identified. Discussion. A priority for future research is to replicate interactions between personality and reaction time in other samples and find specific mechanisms. Stratification of population data on cognitive health by personality and reaction time could improve strategies for identifying those at greater risk of cognitive decline.

Does retirement influence cognitive performance? The Whitehall II Study.

BACKGROUND: Occupational work involves many factors capable of protecting cognition. The 'disuse' hypothesis suggests that removal of such factors at retirement may increase the risk of cognitive decline. OBJECTIVE: To examine whether retirement is significantly associated with cognitive change after adjusting for preretirement cognitive function, personal, social, health and lifestyle factors, work characteristics and leisure activity. METHODS: participants were from the Whitehall II study, a prospective study of London-based Civil Servants. Short-term memory, the AH4 Part 1 (a test of inductive reasoning), verbal fluency and the Mill Hill Vocabulary Scale were collected at ages 38-60 years, and again, on average 5 years later, at 42-67 years, providing pre- and postretirement cognitive functioning assessments for 2031 participants (470 retired and 1561 working). Linear regression was used to test the association between retirement and cognitive performance adjusted for preretirement cognition. RESULTS: Mean cognitive test scores increased between the two assessments. However, after adjusting for age, sex, education, occupational social class, Mill Hill score, work characteristics, leisure activities, and indicators of physical and mental health, those retired showed a trend towards smaller test score increases over 5 years than those still working, although this only reached 5% significance in one test (AH4; ß=-0.7, 95% CI -1.2 to -0.09) and did not show a dose-response effect with respect to length of time in retirement. CONCLUSIONS: This trend is consistent with the disuse hypothesis but requires independent replication before it can be accepted as supportive in this respect.

Intelligence in youth and all-cause-mortality: systematic review with meta-analysis.

BACKGROUND: A number of prospective cohort studies have examined the association between intelligence in childhood or youth and life expectancy in adulthood; however, the effect size of this association is yet to be quantified and previous reviews require updating. METHODS: The systematic review included an electronic search of EMBASE, MEDLINE and PSYCHINFO databases. This yielded 16 unrelated studies that met inclusion criteria, comprising 22,453 deaths among 1,107,022 participants. Heterogeneity was assessed, and fixed effects models were applied to the aggregate data. Publication bias was evaluated, and sensitivity analyses were conducted. RESULTS: A 1-standard deviation (SD) advantage in cognitive test scores was associated with a 24% (95% confidence interval 23-25) lower risk of death, during a 17- to 69-year follow-up. There was little evidence of publication bias (Egger's intercept = 0.10, P = 0.81), and the intelligence-mortality association was similar for men and women. Adjustment for childhood socio-economic status (SES) in the nine studies containing these data had almost no impact on this relationship, suggesting that this is not a confounder of the intelligence-mortality association. Controlling for adult SES in five studies and for education in six studies attenuated the intelligence-mortality hazard ratios by 34 and 54%, respectively. CONCLUSIONS: Future investigations should address the extent to which attenuation of the intelligence-mortality link by adult SES indicators is due to mediation, over-adjustment and/or confounding. The explanation(s) for association between higher early-life intelligence and lower risk of adult mortality require further elucidation.

Direct and indirect pathways connecting cognitive ability with cardiovascular disease risk: socioeconomic status and multiple health behaviors.

OBJECTIVE: To model and test direct and indirect pathways connecting general cognitive ability (g) with cardiovascular disease risk factors, via socioeconomic status (SES) and multiple health behaviors. METHODS: A sample comprising participants in the Health and Lifestyle Survey, a prospective cohort study of a representative sample of U.K. adults in 1984/5 (n = 4939, 2426 males). RESULTS: Two mediating latent variables were proposed that connected a latent cognitive trait (named g) with a latent trait of cardiovascular disease (CVD) risk: multiple health behaviors (defined by smoking, physical inactivity, and weekly saturated fat intake) and SES (defined by educational attainment, occupational social class, and income). In males and females, SES mediated the association between g and CVD risk, but the mediation was moderated by years of age. A direct effect from g to CVD risk was also significant, but this was restricted to older males. Multiple health behaviors offered no explanatory power, because they were not influenced by g. CONCLUSIONS: SES may connect g with CVD risk in males, but not systematically across the life course. Moderated mediation is a novel way to illustrate that direct and indirect pathways can vary as a function of age. Explanations that emphasize g or SES are not mutually exclusive; there are direct and indirect contributions to CVD risk from each source, and these vary across the life course.

IQ in late adolescence/early adulthood, risk factors in middle age, and later cancer mortality in men: the Vietnam Experience Study.

OBJECTIVES: (i) examine the relation, if any, of pre-morbid IQ scores at 20 years of age with the risk of later cancer mortality; and (ii) explore the role, if any, of potential mediating factors (e.g. smoking, obesity), assessed in middle age, in explaining the IQ-cancer relation. METHODS: Cohort study of 14, 491 male, Vietnam-era, former US army personnel with IQ test scores at around 20 years of age (1965-71), who participated in a risk factor survey at around age 38 years of age (1985-6), who were then followed up for mortality experience for 15 years. RESULTS: There were 176 cancer deaths during mortality surveillance. We found an inverse association of IQ with later mortality from all cancers combined (age-adjusted HR(per one SD decrease in IQ); 95% confidence interval: 1.27; 1.10, 1.46) and smoking-related malignancies (1.37; 1.14, 1.64). There was some attenuation following control for mediating variables, particularly smoking and income, but the gradients generally held at conventional levels of statistical significance. CONCLUSIONS: Higher scores on pre-morbid IQ tests are associated with lower risk of later cancer morality. The strength of the relation was partially mediated by established risk factors.