Early-life IQ is a recognized predictor of overall health in late life. Building on this evidence, the present study examined the association between IQ in adolescence and performance-based measures of physical function in old age and tested potential mediators of this association.
Participants (N = 5,750) were from the Wisconsin Longitudinal Study. Measures of IQ and socioeconomic status were obtained in 1957 at about age 18, and measures of peak expiratory flow (PEF), grip strength, chair stand, and gait speed were collected in 2011 at about age 72. Potential mediators (education, adult cognition, disease burden, smoking, physical activity) were obtained in 2003-2005.
Linear regression analysis indicated that higher adolescent IQ was associated with stronger PEF, stronger grip strength, better chair stand performance, faster gait speed, higher physical function composite score, and fewer deficits across domains in old age, controlling for demographic factors. Logistic regression further indicated that higher IQ in adolescence was related to a lower likelihood of PEF less than 80% of predicted value (OR = 0.83, 95%CI = 0.79, 0.88, p <.001), weaker grip strength (OR = 0.88, 95%CI = 0.80-0.97, p=.008), weaker lower limb strength (OR = 0.82, 95%CI = 0.72, 0.93, p = .002) and slow gait speed (OR = 0.81, 95%CI = 0.76, 0.87, p <.001). These associations were mediated by adult cognition and education.
. Higher IQ in adolescence is associated with better physical function in older adulthood.