[Aging of cognitive functions. Results of a longitudinal study]

This study had the two following purposes: to assess the age-related changes in the fluid and crystallized components of intelligence in subjects over age sixty five; to examine whether these age-related changes were linked to any biological, psychological and social factors. The sample was composed of 50 male subjects who were examined three times: in 1968, 1973 and 1977. At the beginning of the study, their age ranged from 60 to 79 years and they were all in good health. In the whole, their socio-economic level was high. At each wave of the study, these subjects were given the same battery of three mental tests: a vocabulary test, selected to assess crystallized intelligence; a perceptual test and a speeded digit coding test, both selected to assess fluid intelligence. Results show that the two components of intelligence have different aging trajectories over age sixty. On the vocabulary test, performances hold until an advanced age (about 75-80), then significantly decline. On the perceptual and digit coding tests, performances sharply and significantly decline with age, this decline looking approximately linear. Whatever the test used, individual differences in age-related changes in performance are found to be great. On vocabulary test, this variability is linked to two factors, independently of age: among subjects who have suffered from a cardio-arterial disease between wave 1 and wave 3, as well as in those who have not maintained an occupational activity, decline in performance is greater than in other subjects. On the two other tests, no factor was found to be significantly linked with change in performance between wave 1 and wave 3.