A growing body of evidence indicates that rates of dementia may be declining, in part because older adults’ cognitive abilities, such as learning and memory functions, are better than those of older adults in the past. But most data have come from almost entirely White cohorts living in high-income countries, calling into question the universality of the trend.
Now, a study of a majority-Black cohort, led by a Boston University School of Public Health (BUSPH) researcher, finds no clear upward trend in cognitive abilities among older adults.
Published in a special supplement to the Journal of Gerontology, the study found trends in cognitive performance differed by race and cognitive function. Although the highest scores in cognitive performance rose in each consecutive round of the study, the lowest scores dropped precipitously. Black participants also scored consistently lower than their White counterparts.
“Our findings suggest that the previously observed upswings in cognitive abilities in older age might not be shared by all groups,” says lead author Dr. Jennifer Weuve, associate professor of epidemiology at BUSPH.
The study used data from the Chicago Health and Aging Project (CHAP), which has followed a total of 10,802 individuals 65 years old or older living on the south side of Chicago since 1993. The cohort is 60 percent Black and 40 percent White by self-identification, meaning it has the greatest number of Black participants — often by an order of magnitude — than any previous comparison of cognitive decline and dementia in Black and White older adults.
The researchers found a modest decline in mean global cognitive scores over the 18-year period. They found a steeper drop in perceptual speed than in episodic memory, with a more pronounced difference in the rate of decline of the two measures among White participants than Black participants.
The disparity between Black and White participants’ mean scores narrowed over the first five of the three-year cycles, from 1993 to 2009, but widened again between 2009 and 2012, especially in the perceptual speed score.