In a new study, scientists have found that stroke claims eight years worth of your brain function.

For the study, data from more than 4,900 black and white seniors over the age of 65 was analysed by a team from the University of Michigan and the VA Center for Clinical Management Research.

They zeroed in on the 7.5 percent of black study participants, and the 6.7 percent 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 the participants' changes in cognitive test scores over time from 1998 to 2012, the researchers could see that 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 that the rates of cognitive problems in older blacks are generally twice that of non-Hispanic whites. So, the new results mean that stroke doesn't account for the mysterious differences in memory and cognition that grow along racial lines as people age.

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

Lead author and assistant professor, Deborah Levine, said that although they 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.

The results are due to be published in the July issue of Stroke.