Catherine M. Calvin

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 (Eggers 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.

Auditory frequency discrimination in adult developmental dyslexics

Developmental dyslexics reportedly discriminate auditory frequency poorly. A recent study found no such deficit. Unlike its predecessors, however, it employed multiple exposures per trial to the standard stimulus. To investigate whether this affects frequency discrimination in dyslexics, a traditional twointerval same-different paradigm (2I_1A_X) and a variant with six A-stimuli per trial (2I_6A_X) were used here. Frequency varied around 500 Hz; interstimulus interval (ISI) ranged between 0 and 1,000 msec. Under 2I_1A_X, dyslexics always had larger just noticeable differences (JNDs) than did controls. Dyslexic and control JNDs were equal at shorter ISIs under 2I_6A_X, but dyslexics became worse than controls at longer ISIs. Signal detection analysis suggests that both sensory variance and trace variance are larger in dyslexics than in controls.

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.

Cognitive ability in early adulthood is associated with systemic inflammation in middle age: The Vietnam experience study

We examined the prospective association between cognitive ability in early adulthood and erythrocyte sedimentation rate, a marker of inflammation, in middle age. Participants were 4256 male Vietnam era US veterans. Data on cognitive ability, assessed by the Army General Technical Test, ethnicity, and place of service were extracted from enlistment files. Smoking behaviour, alcohol consumption, basic socio-demographics, and whether participants suffered from a physician diagnosed chronic disease were determined by telephone interview in middle-age in 1985. Erythrocyte sedimentation rate, cholesterol, blood pressure, height, and weight were measured at a 3-day medical examination in 1986. In linear regression models that adjusted for age and then additionally for circumstantial, socio-demographic, lifestyle, and health factors, poor cognitive ability in early adulthood was associated with greater erythrocyte sedimentation rate in middle age, β=-.09. Thus, it would appear that not only does systemic inflammation influence cognition, but also that poor cognitive ability earlier in life is associated with inflammation in middle-age.

Childhood Intelligence and Midlife Inflammatory and Hemostatic Biomarkers: The National Child Development Study (1958) Cohort

OBJECTIVE In a prospective cohort study the authors examined associations between childhood intelligence at age 11 and inflammatory and hemostatic biomarkers in middle age. METHOD Participants were 9,377 men and women born in the United Kingdom in March 1958, and whose blood plasma samples at age 45 years were analyzed for levels of C-reactive protein (CRP), D-dimer, fibrinogen, tissue plasminogen activator (t-PA) antigen, and von Willebrand factor (VWF). Sex-adjusted linear regression models tested cognition-blood biomarker associations, with and without adjustment for potential confounding by parental socioeconomic status and potential mediation by cardiovascular disease (CVD) risk factors at midlife. Cognitive tests taken at age 50 enabled the inflammation-cognition association to be tested for reverse causation, by adjusting for age 11 intelligence. RESULTS Higher childhood intelligence test scores were significantly associated (p < .001) with lower adult levels of CRP (beta coefficient = -0.068), t-PA antigen (β = -0.014), D-dimer (β = -0.011), fibrinogen (β = -0.011), and VWF antigen (β = -0.008). Early life factors including parental socioeconomic status accounted for 24%-44% of these associations, whereas further adjustment for adult CVD risk factors largely attenuated the effects (82%-100%). The significant inverse associations between age 45 biomarker levels and age 50 cognition could be accounted for to a substantial degree by childhood intelligence (50%-100% attenuation). CONCLUSIONS Childhood intelligence is predictive of inflammatory and hemostatic biomarker status at middle age, which may be largely explained by health behaviors. This highlights the need to consider possible bidirectional associations between cognition and inflammation (and hemostasis) in lifecourse models of CVD-related health.

Childhood Body Weight in Relation to Morbidity From Cardiovascular Disease and Cancer in Older Adulthood: 67-Year Follow-up of Participants in the 1947 Scottish Mental Survey

Although it has been well documented that elevated body weight in middle- and older-aged populations is associated with multiple morbidities, the influence of childhood body weight on health endpoints other than coronary heart disease is not well understood. Accordingly, using a subsample of 4,620 participants (2,288 women) from the Scottish Mental Survey of 1947, we examined the association between body mass index measured at 11 years of age and future risk of 9 independent health endpoints as ascertained from national hospital admissions and cancer registers until 2014 (up to age 77 years). Although there was some evidence of a relationship between elevated childhood body mass index and higher rates of peripheral vascular disease (per each 1-standard deviation increase in body mass index, hazard ratio = 1.21, 95% confidence interval: 1.07, 1.37) and smoking-related cancers (per each 1-standard deviation increase in body mass index, hazard ratio = 1.09, 95% confidence interval: 1.01, 1.17), there was no apparent association with coronary heart disease, stroke (including ischemic stroke), heart failure, or carcinomas of the colorectum, stomach, lung, prostate, or breast. In conclusion, a relationship between childhood body weight and later morbidity was largely lacking in the present study.

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.

Education, employment and school religious denomination in Scotland in the 1950s

Newly available survey data allow the investigation of the educational and employment opportunities open to Roman Catholics in Scotland in the mid-20th century. Previous research has shown that Catholic disadvantage in education and the labour market in the early 20th century had weakened or vanished by the end of the century, and that the main change in that respect had come with the advent of comprehensive secondary schooling in the 1960s. However, the extension of Catholic secondary schooling started in the 1920s. The data used here allow an investigation of whether the Catholic disadvantage was mitigated by these earlier reforms, and thus allow an assessment of whether a selective school system was able to overcome an important dimension of social disadvantage. The data come from a cohort study of a representative sample of people born in 1936 (first surveyed in 1947 and followed up annually to 1963). Evidence is available on social background, on cognitive ability measured at age 11, on secondary school courses, on educational achievement after leaving school, and on social-class status at age 27. The conclusions are that the continued social disadvantage of Catholics was not due to any aspect of the school education which they had received.

Childhood Body Weight in Relation to Cause-Specific Mortality: 67 Year Follow-up of Participants in the 1947 Scottish Mental Survey.

AbstractThe association between childhood body weight and adult health has been little-examined, and findings are inconsistent.In a representative sample of the Scottish nation (the Scottish Mental Survey of 1947), we examined the association between body mass index measured at 11 years of age and future cause-specific mortality by age 77 years. In this cohort study, a maximum of 67 years of follow-up of 3839 study members gave rise to 1568 deaths (758 from cardiovascular disease, 610 from any malignancy). After adjustment for covariates, there was some evidence of a relation between elevated childhood body mass index and rates of mortality ascribed to all-causes (hazard ratio per 1 SD increase in body mass index; 95% confidence interval: 1.09; 1.03, 1.14), cardiovascular disease (1.09; 1.01, 1.17), all cancers combined (1.12; 1.03, 1.21), smoking-related cancers (1.13; 1.03, 1.25), and breast cancer in women (1.27; 1.04, 1.56).In conclusion, we provide further observational evidence for the need for weight control measures in youth.