Objective: To examine the association between cognitive ability in childhood and mid-life cognitive decline in the normal population.
Design: Longitudinal, population based, birth cohort study.
Participants: 2058 men and women born in 1946.
Main study measures: Ability in childhood measured by AH4 and test of verbal comprehension at age 15 years. Ability in adulthood measured by the national adult reading test (NART) at age 53 years. Outcome measures were decline in memory (word list learning) and speed and concentration (timed visual search) from age 43 to 53 years.
Results: Ability in childhood was significantly and negatively associated with decline in memory (beta = 0.09, P = 0.005, for men; 0.10, P < 0.001, for women) and search speed (beta = 0.13, P < 0.001, for men; 0.08, P = 0.01, for women), independent of educational attainment, occupational social class, and a range of health indicators. The adult reading test was also significantly and negatively associated with decline in these outcomes (for memory beta = 0.21, P < 0.001, for men; 0.17, P < 0.001, for women; and for search speed beta = -0.05 for men; 0.10, P = 0.008 for women) independent of educational attainment, social class, and childhood ability.
Conclusions: Ability in childhood can protect against cognitive decline in mid-life and beyond. Results for the adult reading test indicate that the protective effect of ability may also be acquired in adulthood.