Men who sleep for a long time may be in far greater danger of having a stroke, according to a study.
It found white men who habitually spend more than nine hours a night asleep have a 70 % higher risk.
However, this effect was not found among black men or women of either race who had a long night’s sleep. The US researchers said further studies were needed to explain the differences.
They followed more than 16,000 people with an average age 64 for around six years, during which 460 of them suffered a stroke. They also found black men who slept less than six hours a night were 80 % less likely to later have a stroke compared with black men who were average sleepers.
This protection for short sleepers was not present for white men and women of both races.
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.’
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’. It may also be a sign of other health problems or cause inflammation that could contribute to a stroke.
Dr Howard said: ‘The results suggest short and long sleep duration may have different consequences depending on race and sex.’ Dr Megan Petrov, who led the study, said: ‘There is evidence suggesting men and women get different average amounts of sleep for various behavioural, cultural, and environmental reasons.
‘Those differences in sleep amount, combined with physiological differences between men and women such as in hormone levels, may increase risk for stroke.’