Aggregate changes in severe cognitive impairment among older Americans: 1993 and 1998

Objectives. This study explored whether improvements in cognitive functioni ng occurred during the 1990s among older Americans and investigated several possible explanations for such changes. Methods. Using the 1993 Asset and Health Dynamics of the Oldest Old study ( N = 7,443) and 1998 Health and Retirement Survey (N = 7.624). this study ex amined aggregate changes in the proportion of the noninstitutionalized popu lation aged 70 and older with severe cognitive impairment. impairment was m easured for self-respondents using a modified version of the Telephone Inte rview Cognitive Screen: for proxy respondents, ratings of memory and judgme nt were used. Logistic regression was used to investigate potential explana tions for aggregate changes. Results. The percentage of older Americans with severe cognitive impairment declined from 6.1% in 1993 to 3.6% in 1998 (p < .001). The decline was sta tistically significant among self-respondents bur nor among those with prox y interviews. Improvements between 1993 and 1998 were not explained by shif ts in demographic and socioeconomic factors or by changes in the prevalence of stroke, vision, or hearing impairments. Discussion. As a group, older persons, especially those well into their 80s , appear to have better cognitive functioning today than they did in the ea rly 1990s.