Cognitive functioning in centenarians: a coordinated analysis of results from three countries.

Cognitive functions among centenarians in Japan, Sweden, and the United States are described. Three areas are explored. First, definitions and prevalence of dementia are compared between Japan and SWEDEN: Second, levels of cognitive performances between centenarians and younger age groups are presented. Third, interindividual variations in cognitive performances in centenarians and younger persons are compared in Sweden and the United STATES: The Swedish and Japanese studies show a variation in prevalence of dementia between 40% and 63% with a relatively higher prevalence among women. Part of the variance is probably due to differences in sampling and criteria of dementia. Along with the lower cognitive performance in centenarians, compared with younger age groups, the Swedish and U.S. results show a wider range of performance among centenarians for those semantic or experientially related abilities that tend to be maintained over the adult life span. In contrast, a smaller range of performance is found for centenarians on those fluid or process-related abilities that have shown a downward age-related trajectory of performance. Lower variability is probably due to centenarians reaching the lower performance limit. The conclusions agree with the assumption of a general increase in cognitive differentiation with increasing age, primarily in measures of crystallized intelligence. The conclusions point to the general robustness of results across countries, as well as to the relative importance of cognition for longevity.