An intelligent mind in a healthy body? Predicting health by cognitive ability in a large European sample

Intelligence has been consistently demonstrated to be a predictor of health outcomes. However, the exact mechanisms are subject of debate. Environmental and behavioral risk factors have been suggested to affect the intelligence-health association, but the available literature has mostly focused on children and young adults. Here, we aimed to investigate the intelligence-health association in older adults. We analyzed data from the Study of Health and Retirement in Europe (SHARE), a representative longitudinal survey in which participants above 50 years of age (N range = 10,000-30,000+) were interviewed in seven waves from 2004 to 2017. Indicators of physical and mental health (e.g., number of symptoms; self-reported depression) were associated with cognitive function variables (mathematical reasoning, word recall, verbal fluency) which were used as proxy measures for intelligence. Behavioral and environmental risk factors (e.g., legal drug consumption, physical inactivity, work environment) were examined as potential moderator variables for the intelligence-health association. More favorable health outcomes were modestly, but consistently associated with higher cognitive ability across variables (r range = |0.13|-|0.29|). Mixed-model Poisson regression analyses showed a reduction of 11% in self-reported symptom numbers with each unit increase in mathematical reasoning. Environmental and behavioral risk factors exhibited mostly trivial moderating effects on the intelligence-health association. Our findings reveal a positive association of intelligence and health in a representative longitudinal European sample. Environmental and behavioral risk factors offered little explanatory value for this association, suggesting a different underlying mechanism such as a general fitness factor that affects both intelligence and health.