Background People with higher intelligence in early life have a lower subsequent risk of coronary heart disease events, but the explanation for these observations is unclear.
Aims To examine whether intelligence in early adulthood is associated with risk of subclinical atherosclerosis in mid-life, as indicated by the ankle brachial index (ABI), and investigate its potential mediating role in the association between intelligence and mortality.
Methods Participants were 4286 male US veterans whose intelligence was measured on enlistment into military service at a mean age of 20.4 years and whose ABI was measured by Doppler as part of a detailed medical examination at a mean age of 38.3 years.
Results Higher intelligence in early adulthood was associated with a higher ABI in mid-life. For an SD increase in intelligence, after adjusting for age, ABI (×10) rose by 0.05 (0.02, 0.07), and the OR (95% CI) for having a low ABI (≤0.90) was 0.84 (0.72 to 0.98). Further adjustment for smoking, serum cholesterol, triglycerides and glucose concentrations, blood pressure, erythrocyte sedimentation rate, body mass index, alcohol intake, education and measures of socioeconomic position had little or no attenuating effect on these associations. Lower ABI was associated with increased mortality from all causes and cardiovascular disease but it did not account for the associations between IQ and mortality from these causes.
Conclusions Men of lower intelligence may be more susceptible to atherogenesis, though this mechanism does not appear to explain their increased risk of earlier death.
- cognitive problems
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Funding The Centre for Cognitive Ageing and Cognitive Epidemiology is funded by the Biotechnology Sciences Research Council, the Engineering and Physical Sciences Research Council, the Economic and Social Research Council, the Medical Research Council and the University of Edinburgh as part of the cross-council Lifelong Health and Wellbeing initiative. The Medical Research Council Social and Public Health Sciences Unit receives funding from the Medical Research Council and the Chief Scientist Office at the Scottish Government Health Directorates. GDB is a Wellcome Trust Fellow (WBS U.130.00.006.00012.01).
Competing interests None declared.
Ethics approval Ethical approval for the study protocol was given by the US Office for Technology Assessment, the Department of Health and Human Sciences Advisory Committee, the Agent Orange Working Group Science Panel and a review panel from the US Centers for Disease Control.
Provenance and peer review Not commissioned; externally peer reviewed.