Having a stroke ages a person’s brain function by almost eight years — robbing them of memory and thinking speed as measured on cognitive tests, according to a new study.

OT_News-01In both black and white patients, having had a stroke meant their scores on a 27-item test of memory and thinking speed had dropped as much as it would have if the patients had aged 7.9 years overnight.

The study was conducted by a team from the University of Michigan’s schools of medicine and public health and the VA Center for Clinical Management Research, all in Ann Arbor. The results were published online May 21 and will appear in the July issue of the journal Stroke.

For the study, investigators analyzed data from more than 4,900 black and white people older than 65 years. To collect the data, researchers married two sources of information: detailed surveys and tests of memory and thinking speed during multiple years from participants in a large, national study of older Americans, and Medicare data from the same individuals.

They focused on the 7.5% of black study participants and the 6.7% of white participants who had no recent history of stroke, dementia or other cognitive issues, but who suffered a documented stroke within 12 years of their first survey and cognitive test in 1998.

By measuring participants’ changes in cognitive test scores during the time period from 1998 to 2012, the researchers found both blacks and whites did significantly worse on the test after their stroke than they had before.

Although the size of the effect was the same among blacks and whites, past research has shown the rates of cognitive problems in older blacks are generally twice that of non-Hispanic whites. So the new results mean stroke doesn’t account for the mysterious differences in memory and cognition that grow along racial lines as people age, according to the investigators.

The researchers said the findings underscore the importance of stroke prevention.

“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,” lead author Deborah Levine, MD, MPH, U-M Medical School assistant professor, said in a news release. “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.”

Past research on disparities in cognitive decline has focused on racial differences in socioeconomic status, education and vascular risk factors such as diabetes, high blood pressure and smoking that can all contribute to stroke risk. These factors might explain some but not all of the racial differences in cognitive decline.

Levine and her colleagues note certain factors — such as how many years a person has vascular risk factors, the quality of his or her education, and genetic and biological factors — might play a role in racial differences in long-term cognitive performance.

The study was funded by grants from the National Institutes of Health.

The study’s co-authors include Mohammed Kabeto, MS; Kenneth Langa, MD, PhD; and Mary A.M. Rogers, PhD, of the U-M Medical School’s Division of General Medicine; and Lynda Lisabeth, PhD, and Andrzej Galecki, MD, PhD, of the U-M School of Public Health.

Langa holds a joint position at the U-M Institute for Social Research, which runs the Health and Retirement Survey, the large national longitudinal study from which the data were drawn. Levine and Langa are members of the VA CCMR, based at the VA Ann Arbor Healthcare System. Levine and Lisabeth also hold positions in the Medical School Department of Neurology. Levine, Langa, Lisabeth and Rogers are members of the U-M Institute for Healthcare Policy and Innovation.

Study abstract: http://stroke.ahajournals.org/content/early/2015/05/20/STROKEAHA.114.008156.abstract