May 13, 2008 Those with at least a high school education spend more of their older years without cognitive loss -- including the effects of Alzheimer's, Parkinson's and dementia -- but die sooner after the loss becomes apparent, reveals a new study.
"These findings are consistent with the idea that those with more education may process tasks more efficiently or use other compensatory mechanisms that delay cognitive impairment or delay our ability to detect impairment," explained USC Davis School of Gerontology professor Eileen Crimmins, corresponding author of the study.
Using a nationally representative survey, Crimmins and her co-authors tracked more than 7,000 people over the age of 70 for seven years. They found that a 70-year old person with at least 12 years of education can expect:
- To live 14.1 more years without cognitive impairment, two-and-a-half years more than 70-year olds with fewer than 12 years of education.
- To spend 1 year of remaining life with impairment, about 7 months less than a person with fewer years of education.
"One implication of these findings is that as education increases in the population, the length of time spent with cognitive impairment should be reduced," Crimmins said.
However, those with more education appeared to exhibit more severe cognitive impairment -- which may include memory loss, loss of language or disorientation -- and to be in worse health, the researchers found.
"Surprisingly, the risk of dying among those with cognitive impairment is generally higher for the more educated than for the low education group, even though the possibility of becoming cognitively impaired is lower for the higher education group," Crimmins said.
For example, 80-year olds with at least a high school education have a 23 percent chance of dying within a year after severe mental loss -- about 6 percentage points more likely than less-educated 80-year olds with impairment and four times more likely than 80-year olds who are mentally sound.
Still, the researchers found that there is some chance of recovery from severe cognitive loss in large populations. Overall, about 11 percent of the mentally impaired will recover, according to the study.
The researchers hypothesize that those with treatable conditions such as depression and those recovering from strokes or cancer treatments are more likely to regain mental abilities. Specifically, they find that stroke is almost twice as prevalent among the highly educated who recover than among those who remain impaired.
"The length of life with cognitive impairment will increase as total life expectancy increases, unless the age at onset of cognitive impairment is delayed, perhaps by addressing modifiable risk factors," Crimmins said. "Cognitive impairment is a major health problem in old age and an area of growing concern for population health."
The research was supported by the National Institute of Aging, the Institute for Longevity and Aging and the Robert Wood Johnson Foundation's Health & Society Scholars Program.
Agnès Lièvre (Institut National d'Etudes Démographiques, France), who was a postdoctoral student at USC, is the lead author of the study. Dawn Alley (University of Pennsylvania), who received her Ph.D. from USC, was also an author of the study.
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- A. Lievre, D. Alley, E. M. Crimmins. Educational Differentials in Life Expectancy With Cognitive Impairment Among the Elderly in the United States. Journal of Aging and Health, 2008; 20 (4): 456 DOI: 10.1177/0898264308315857
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