White men who habitually sleep nine or more hours a night have 71 per cent greater odds of having a stroke, a study has found.
But black men do not face a lower risk for sleeping too long, and even appear to be offered protection by sleeping less than six hours a night.
Researchers followed more than 16,000 people aged 45 and over for an average of six years, during which 460 of them suffered a stroke.
Their study found white men, but not women, were at greater risk if they were long sleepers compared to those who got an average night’s sleep.
The results – which found a difference in stroke rates between white and black men – suggest sleep also affects people of different races differently.
Sleeping too long may be a warning sign of a health problem for white men, researchers believe.
They added it may just be part of an unhealthy sedentary lifestyle which makes men more vulnerable to strokes.
Dr Virginia Howard, co-author of the study from the University of Alabama at Birmingham, said: ‘More research is needed to determine the mechanisms behind these relationships.
‘In the meantime, this emphasises how important it is to better monitor and control cardiovascular risk factors in middle-aged to older people who have long sleep periods.’
While we are often told to get more shut-eye, a British study this year reported that nine hours of sleep raises the risk of early death by 14 per cent.
The latest study, whose participants had an average age of 64, asked people how long they slept during week days and weekends.
The results put long-sleeping white men who got nine or more hours a night at a 71 per cent higher risk of a stroke than male white average sleepers.
White women did not affect their risk of stroke, regardless of how long they slept, which more research needs to be done to understand.
The authors, writing in the journal Neurology, said ‘long sleep duration may be contributing to an overall sedentary lifestyle through greater time spent in bed and less energy expenditure’.
But it may also be a sign of health problems in healthy adults, or cause inflammation, which may contribute to a stroke.
The study found that black men who slept less than six hours per night were about 80 per cent less likely to later have a stroke when compared to black men who were average sleepers.
This protection for short sleepers was not present for black women, white men or white women.
In their analysis, researchers adjusted for other factors that could affect stroke risk, such as smoking status, diabetes and heart disease.
Dr Howard said: ‘These results suggest that short and long sleep duration may have different consequences for people depending on race and sex.’