Aggregate Changes in Severe Cognitive Impairment Among Older Americans: 1993 and 1998

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Abstract
Objectives. This study explored whether improvements in cognitive functioning 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 examined aggregate changes in the proportion of the noninstitutionalized population aged 70 and older with severe cognitive impairment. Impairment was measured for self-respondents using a modified version of the Telephone Interview Cognitive Screen; for proxy respondents, ratings of memory and judgment were used. Logistic regression was used to investigate potential explanations 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 statistically significant among self-respondents but not among those with proxy interviews. Improvements between 1993 and 1998 were not explained by shifts 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 early 1990s.

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