In a study investigating the different levels of cognitive decline between black and white people, stroke could not explain the disparity, and instead showed the same impact across races – to result in a loss of cognitive function equivalent to the brain aging by an average of 8 years.
In both the black and white patients studied, having had a stroke meant that their score on a 27-item test of memory and thinking speed had dropped as much as it would have if they had aged 7.9 years overnight.
The results come from an analysis of data from over 4,900 black and white seniors aged over 65 years, published in the journal Stroke.
The research team comes from the University of Michigan U-M Medical School and School of Public Health in Ann Arbor, and it worked with the VA Center for Clinical Management Research in the same city.
Lead author of the study is Dr. Deborah Levine, assistant professor at U-M Medical School, who says:
“As we search for the key drivers of the known disparities in cognitive decline between blacks and whites, we focus here on the role of ‘health shocks’ such as stroke.”
“Although we found that stroke does not explain the difference,” she adds, “these results show the amount of cognitive aging that stroke brings on, and therefore the importance of stroke prevention to reduce the risk of cognitive decline.”
The analysis used detailed surveys and tests of memory and thinking speed over multiple years. It was a large, national study of older Americans that also used Medicare data.
The researchers narrowed down to those participants with no history of stroke, dementia or other cognitive issues recently, but instead within 12 years of their first survey and cognitive test done for the research in 1998 – representing 7.5% of black study participants and 6.7% of white.
The measure of a stroke’s effect on brain power was achieved by measuring changes in cognitive test scores over time from 1998 to 2012.
Both black people and white fared significantly worse on these tests after their stroke compared with performance before stroke.
The researchers say that racial differences on overall levels of cognitive decline remain in need of explanation but that “one thing is clear: strokes have serious consequences for brain function.”
Therefore, they add, people of all racial and ethnic backgrounds can benefit from taking steps to reduce their risk of a stroke.
Such stroke preventive steps include:
- Controlling blood pressure and cholesterol
- Stopping or avoiding smoking
- Controlling blood sugar in diabetes
- Maintaining physical activity.
Although the size of the stroke effect on cognitive decline was the same among blacks and whites in this study, past research has shown that, generally, the rates of cognitive problems in older non-Hispanic white people are half those of older black people.
The results suggest that stroke can be ruled out as accounting for “the mysterious differences in memory and cognition that grow along racial lines as people age.”
While this study looked for any stroke racial differences, and found none, other studies on the race disparities in cognitive decline have focused on socioeconomic status, education and vascular risk factors for stroke such as diabetes, high blood pressure and smoking.
The authors explain that, as well as genetic and biological factors, the number of years a person has vascular risk factors and the quality of their education may play a role in racial differences in long-term cognitive performance. However, these factors may explain some but not all of the racial differences.