Background Studies with single baseline measurements of cognitive function consistently reveal inverse relationships with mortality risk. The relation of change in functioning, particularly from early in the life course, which may offer additional insights into causality, has not, to the best of our knowledge, been tested.
Aims To examine the association of change in cognition between late adolescence and middle age with cause-specific mortality using data from a prospective cohort study.
Methods The analytical sample consisted of 4289 former US male military personnel who were administered the Army General Technical Test in early adulthood (mean age 20.4 years) and again in middle age (mean age 38.3 years).
Results A 15-year period of mortality surveillance subsequent to the second phase of cognitive testing gave rise to 237 deaths. Following adjustment for age, a 10-unit increase in cognitive function was related to a reduced risk of death from all causes (HR 0.84; 95% CI 0.75 to 0.93) and cardiovascular disease (HR 0.78; 95% CI 0.64 to 0.95) but not from all cancers (HR 1.14; 95% CI 0.88 to 1.47) nor injury (HR 1.02; 95% CI 0.81 to 1.29). Adjustment for markers of socioeconomic status in middle age resulted in marked attenuation in the magnitude of these associations and statistical significance at conventional levels was lost in all analyses.
Conclusions In the present study, the apparent link between increased cognition and mortality was mediated by socioeconomic status.
- cognitive function
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Contributors GDB developed the idea for these analyses and agreed an analytical plan with MJS. MJS conducted all data analyses and prepared the tables of results. GDB wrote the first version of the manuscript on which all authors commented.
Funding Mortality surveillance of study members in the Vietnam Experience Study was funded by the National Center for Environmental Health in Atlanta, USA. MJS is supported by the British Heart Foundation, and GDB by the UK Medical Research Council (MR/P023444/1) and the US National Institute on Aging (1R56AG052519-01; 1R01AG052519-01A1).
Competing interests None declared.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data may be requested from a third party - the US Centers for Disease Control and Prevention - and are not publicly available.