Are individual differences in rates of aging greater at older ages?

Although differences among people are frequently assumed to increase with age, cross-sectional comparisons of measures of brain structure and measures of cognitive functioning often reveal similar magnitudes of between-person variability across most of adulthood. The phenomenon of nearly constant variability despite systematically lower means with increased age suggests that individual differences in rates of aging may be relatively small, particularly compared with the individual differences apparent at any age. The current study examined between-person variability in cross-sectional means and in short-term longitudinal changes in 5 cognitive abilities at different ages in adulthood. The variability in both level and change in cognitive performance was found to be similar among healthy adults from 25 to 75 years of age in all 5 cognitive abilities. Furthermore, the correlations between scores at the first and second occasions were very high, and nearly the same magnitude at all ages. The results indicate that between-person differences in short-term cognitive changes are not inevitably greater among healthy older adults than among young adults.