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Disability Rises Gradually for a Cohort of Older Americans

Objectives
We study changes in average disability over nearly two decades for a large epidemiological cohort of older Americans. As some people exit by mortality, do average disability levels for the living cohort rise rapidly, rise gradually, stay steady, or decline?


Method
Data are from the Study of Asset and Health Dynamics Among the Oldest Old (AHEAD) cohort for 1993-2010. Cohort members are aged 70+ in 1993 (mean = 77.5 years), and the survivors are aged 87+ in 2010 (mean = 90.2 years). Personal care disability (activities of daily living), household management disability (instrumental activities of daily living), and physical limitations are studied. We study average disability for the living cohort over time and the disability histories for decedent and survivor groups.


Results
Average disability rises gradually over time for the living cohort. Earlier decedent groups have higher average disability than later ones. Near death, disability rises sharply for all decedent groups. Longer surviving groups have less average disability, and slower disability increases, than shorter surviving groups. All results are repeated for younger cohort members (baseline age = 70-79 years), older ones (baseline age = 80+ years), women, and men.


Discussion
As a cohort ages, average disability among living members increases gradually, signaling behavioral, psychological, and biological fitness in very old persons.