A University of Michigan study of nearly 5,000 people found that experiencing a stroke alters memory and thinking speed as if the person had aged eight years overnight.
Researchers were looking for an explanation for cognitive decline in older black people being about twice that of non-Hispanic white people, however in the case of strokes the decline is the same.
"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," said UM Medical School assistant professor Deborah Levine, M.D., in a press 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."
For the study, 4,900 participants over the age of 65 took surveys, memory tests and cognitive tests from 1998 to 2012, and researchers measured the rate of change in test scores.
Researchers focused on the 7.5 percent of black participants and 6.7 percent of white participants who had no recent history of stroke but who had a stroke within 12 years of the first test in 1998. Test scores showed significant cognitive decline after stroke, and the effect was equal among black and white participants -- equivalent to aging 7.9 years.
Other research has shown that a range of factors can affect the decline in cognitive ability of people overall, noting that years a person has vascular risk factors, and the quality of his or her education, as well as genetic and biological factors can all contribute to overall decline in brain function. Stroke, however, has a demonstrable, equivalent detrimental effect on the brain for all people, researchers said.