Neurology Central

Cognitive function: 8 years gone in a stroke

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A study investigating the impact of stroke on neurological function has recently been carried out by investigators at University of Michigan (MI, USA). The study, which aimed to determine if there is a link between stroke and the disparities in cognitive health observed amongst elderly black and white individuals, determined that incident stroke results in a decrease in global cognition equivalent to almost 8 years of aging. These results, which were not observed to differ based on race, appear in the July issue of Stroke.

The team focused on testing both memory and thinking speed in order to examine the impact of stroke and other such ‘health shocks’ on participants’ neurological faculties. Utilizing a 27-item memory and thinking speed test, they demonstrated that incident stroke resulted in a decrease in global cognition equivalent to 7.9 years of cognitive aging.

It is as yet unknown whether the greater risk of dementia observed amongst black individuals can be attributed to the differences in acute stroke compared with white individuals, the impact of stroke on cognitive function or other factors.

Data for the analysis were taken from the national population-based Health and Retirement Study linked with Medicare data (ranging from 1998 to 2012), accounting for 4908 individuals ≥65 years of age (453 black, 4455 white). This information was then utilized to examine the difference in frequency, along with variation in the impact of stroke, among black and white individuals. Within this cohort, the team identified 7.5% of black participants and 6.7% of white participants with no recent history of stroke, dementia or cognitive impairment, who were documented as having experienced an incident stroke within 12 years of their first survey in 1998.

The results demonstrated that the impact of incident stroke on cognitive function did not differ based on race, with variations in test scores that aligned with greater cognitive dysfunction in both black and white individuals following stroke.

The rate of cognitive issues among older black individuals has previously been observed at approximately double that of the non-Hispanic white population. Past studies have focused on racial differences in socioeconomic status, access to and quality of education, as well as vascular risk factors, such as smoking, diabetes and high blood pressure as causes for the greater incidence of cognitive decline.

The authors comment that a combination of factors – comprising vascular risk factors, quality of education, and genetic and biological factors – may contribute to the black–white racial variations in long-term cognitive health among the elderly population.

“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,” remarked lead author Deborah Levine (University of Michigan Medical School). “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.”

Emphasizing the major impact of stroke on cognitive deterioration, this study further reinforces the importance of stroke prevention. The possible explanation for racial disparities in cognitive health observed amongst blacks and whites, however, still remains elusive.

Sources: Levine DA, Kabeto M, Langa KM, Lisabeth LD, Rogers MAM, Galecki AT. Does stroke contribute to racial differences in cognitive decline? Stroke doi: 10.1161/STROKEAHA.114.008156 (2015) (Epub ahead of print); University of Michigan press release

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