Aggregate changes in severe cognitive impairment among older Americans: 1993 and 1998
Freedman,Vicki A.; Aykan,Hakan; Martin,Linda G.
Journal of Gerontology 56B(2): S100-S111
Publication date: 2001
This study explored whether improvements in cognitivefunctioning occurred during the 1990s among older Americansand investigated several possible explanations for such changes.
Using the 1993 Asset and Health Dynamics of the OldestOld study (N = 7,443) and 1998 Health and Retirement Survey(N = 7,624), this study examined aggregate changes in the proportionof the noninstitutionalized population aged 70 and older withsevere cognitive impairment. Impairment was measured for self-respondentsusing a modified version of the Telephone Interview CognitiveScreen; for proxy respondents, ratings of memory and judgmentwere used. Logistic regression was used to investigate potentialexplanations for aggregate changes.
The percentage of older Americans with severe cognitiveimpairment declined from 6.1% in 1993 to 3.6% in 1998 (p <.001). The decline was statistically significant among self-respondentsbut not among those with proxy interviews. Improvements between1993 and 1998 were not explained by shifts in demographic andsocioeconomic factors or by changes in the prevalence of stroke,vision, or hearing impairments.
As a group, older persons, especially those wellinto their 80s, appear to have better cognitive functioningtoday than they did in the early 1990s.