There is no link between cognitive decline and socio-economic status in people aged 70 and older, a new study has found.
However, the study, led by researchers at the University of California-Los Angeles (UCLA), has shown that seniors who have never been married, and widowers, seem to perform more poorly as they age,.
Published in the American Journal of Epidemiology, the study of older Americans 70-plus years of age (mean age 75) found that rates of cognitive decline over a nine-year period were similar across socio-economic and racial and ethnic groups.
The findings made by experts from the David Geffen School of Medicine at UCLA and the UCLA School of Public Health indicate that disparities in cognitive functioning among older Americans of different groups are almost entirely due to differences in the cognitive peaks they reached earlier in life, not to differences in rates of decline.
"It has been known that cognitive performance at any given age appears to depend on demographic characteristics; the more educated, for instance, perform better," said lead investigator Dr. Arun Karlamangla, associate professor of medicine in the division of geriatrics at the Geffen School of Medicine.
"But though there are differences in the level of performance you start with in your late 60s, this study's surprise is that the rate of decline in your 70s is the same for every group," he added.
The study was based on data from 6,476 adults born prior to 1924 culled from the Study of Assets and Health Dynamics Among the Oldest Old (AHEAD).
The researchers tested the subjects five times between 1993 and 2002 on various memory and cognition items, including word recall, the "serial sevens" subtraction test, orientation to time, attention, language and knowledge of current affairs.
Though they found evidence of a link between socio-economic status (SES) and cognition, it was only at baseline - that is, the first test.
The researchers observed that the participants with high SES performed better on the first assessment than those with middle SES, who in turn performed better than individuals with low SES.
They said that such differences could be linked to the effects of education, such as learned test-taking strategies, and the possible direct effects of education on brain structure.
They did find some demographic variation in rates of cognitive decline, with older participants declining faster than younger ones, and widows and widowers and those who never married declining faster than married individuals.
"The most consistent predictors of faster declines in cognitive functioning were being old and being single," the researchers wrote.
The team noted that there were some potential limitations to the study. Though few associations between socio-economic status and the rate of cognitive decline were found in the AHEAD total cognition score, an association might emerge in other cognition domains not examined in the study.
According to them, there was a greater drop-off during the follow-up period among participants with low socio-economic status and among low-functioning individuals, possibly skewing results.
Furthermore, differences between groups in physical health were not controlled during the National Institute on Aging-funded study.