Getting too much sleep may be bad for your heart, a new study suggests.
The amount of time a person sleeps has been linked to their risk of cardiovascular disease and premature death.
The research, published in the European Heart Journal, examined data on 116,000 people aged between 35 and 70 from 21 different countries.
After an average follow-up period of nearly eight years, researchers recorded 4381 deaths and 4365 "major cardiovascular events".
People who slept longer than eight hours had a higher risk of dying or developing diseases of the heart or blood vessels in the brain compared to those who slept for between six and eight hours.
"Sleep is essential to human health, and people spend about a third of their hours sleeping. It is increasingly regarded as an important lifestyle behaviour that can affect cardiovascular disease (CVD) and death," the team of international researchers wrote.
Compared to people who slept six to eight hours, those who slept a total of eight to nine hours a day had a 5 per cent increased risk; people sleeping between nine and 10 hours a day had an increased risk of 17 per cent and those sleeping more than 10 hours a day carried a 41 per cent increased risk of cardiovascular disease or death.
The researchers also found a 9 per cent increased risk for people who slept a total of six or fewer hours, but this finding was not statistically significant.
"Our study shows that the optimal duration of estimated sleep is six to eight hours per day for adults," said lead author Chuangshi Wang, a PhD student at McMaster and Peking Union Medical College, Chinese Academy of Medical Sciences, China.
Co- author Professor Salim Yusuf, from McMaster University, Ontario, Canada, added: "The general public should ensure that they get about six to eight hours of sleep a day.
"On the other hand, if you sleep too much regularly, say more than nine hours a day, then you may want to visit a doctor to check your overall health.
"For doctors, including questions about the duration of sleep and daytime naps in the clinical histories of your patients may be helpful in identifying people at high risk of heart and blood vessel problems or death."