According to a new study from researchers at the University of Michigan Health System, having a stroke will age your cognitive function by nearly eight years, underscoring the importance of stroke prevention.
As if often the case in science, discoveries come by accident. In this case, researchers were chasing down a hypothesis regarding whether or not the frequency and impact of strokes differed between black and white individuals and if that contributed to the noted racial disparity in cognitive decline data.
The study, “Does Stroke Contribute to Racial Differences in Cognitive Decline?,” will be published in the July issue of Stroke. It looked at 4908 black and white participants over the age of 65 with data taken from the nationally representative Health and Retirement Study with linked Medicare data (1998–2010). Researchers conducted what is known as a longitudinal study.
Translation: A longitudinal study is an observational (does not interact with research subjects) research method in which researchers will gather relevant data for the same group of people over a long period of time, years or even decades.
Controlling for initial cognitive function and demographics, the researchers explained that “[they] identified 34 of 453 (7.5%) blacks and 300 of 4455 (6.7%) whites with incident stroke over a mean (SD) of 4.1 (1.9) years of follow-up (P=0.53). Blacks had greater cognitive decline than whites (adjusted difference in modified version of the Telephone Interview for Cognitive Status score, 1.47 points; 95% confidence interval, 1.21 to 1.73 points). With further adjustment for cumulative incidence of stroke, the black–white difference in cognitive decline persisted.”
In other words, the team focused on a small group of black and white individuals with no history of stroke (or other cognitive issue), but who suffered a documented stroke within 12 years of their first survey and cognitive test in 1998. While the data showed black individuals showing more cognitive decline as expected, it was not associated with incidence of stroke.
They continue on to say that “incident stroke was associated with a decrease in global cognition (1.21 points; P<0.001) corresponding to ≈7.9 years of cognitive aging. The effect of incident stroke on cognition did not statistically differ by race (P=0.52).” Basically, for both black and white individuals, a stroke aged their cognitive function by essentially eight years. A 50 year-old person who experienced a stroke would then show the cognitive function of a 58 year-old.
Lead author, Deborah Levine, M.D., MPH, explained how their results came about in a statement through the university. “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, 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.”