Objectives: low cognitive ability is associated with subsequent functional disability. Whether this association extends across adult life has been little studied. The aim of this study was to examine the association between intellectual ability in young adulthood and physical functioning during a 10-year follow-up in older age.
Methods: three hundred and sixty persons of the Helsinki Birth Cohort Study (HBCS) male members, born between 1934 and 1944 and residing in Finland in 1971, took part in The Finnish Defence Forces Basic Intellectual Ability Test during the first 2 weeks of their military service training between 1952 and 1972. Their physical functioning was assessed twice using the Short Form 36 (SF-36) questionnaire at average ages of 61 and 71 years. A longitudinal path model linking Intellectual Ability Test score to the physical functioning assessments was used to explore the effect of intellectual ability in young adulthood on physical functioning in older age.
Results: after adjustments for age at measurement, childhood socioeconomic status and adult BMI (kg/m2), better intellectual ability total and arithmetic and verbal reasoning subtest scores in young adulthood predicted better physical functioning at age 61 years (P values <0.021). Intellectual ability total and arithmetic and verbal reasoning subtest scores in young adulthood had indirect effects on physical functioning at age 71 years (P values <0.022) through better physical functioning at age 61 years. Adjustment for main chronic diseases did not change the results materially.
Conclusion: better early-life intellectual ability helps in maintaining better physical functioning in older age.