Trends in scores on tests of cognitive ability in the elderly US population, 1993-2000

Objective. This study investigates cohort differences in cognitive functioning among Americans aged 70 or older in 1993, 1995, 1998, and 2000. Methods. The study draws on self-respondent data from four waves of the Asset and Health Dynamics Among the Oldest Old Study and the Health and Retirement Study surveys collected between 1993 and 2000. Cognitive performance scores for each of four components (immediate recall, delayed recall, serial 7s, and mental status) and their sum are compared across cohorts, unadjusted and with adjustments for survey design features and demographic characteristics. Results. Unadjusted scores suggest cohort improvements in several components of cognitive functioning between 1993 and 1998, and little change between 1998 and 2000. However, these improvements largely disappear after confounding features of the survey design (changes in age distribution of the sample across waves and prior exposure to the cognitive tests) and changes in the demographic composition of the sample (race, ethnicity, and gender) are adjusted for. Discussion. There appears to have been little improvement of cognitive functioning across recent cohorts of older Americans. However, the study points out the complexities of using panel data to study cohort differences, particularly when the measures of interest are likely influenced by prior wave participation. Future studies based on other data sources are needed.