Researchers examined data from nearly 117,00 adults, aged 35 to 70, in 21 countries who were followed for an average of nearly eight years, CNN reported.
Rates of heart disease (such as stroke or heart failure) and death were 7.8 per 1,000 among those who slept the recommended six to eight hours per night, compared with 8.4 per 1,000 among those who slept eight to nine hours, 10.4 per 1,000 among those who slept nine to 10 hours, and 14.8 per 1,000 among those who slept more than 10 hours a night.
That translates into a 5 percent, 17 percent and 41 percent increased risk, respectively, CNNreported.
The rate among people who slept six or less hours a night was 9.4 per 1,000, or 9 percent higher than those who got the recommended amount of sleep, but this was statistically insignificant, according to Chuangshi Wang, McMaster and Peking Union Medical College, China, and colleagues.
They said the increased risk of heart disease and death in people who sleep more than the recommended amount may be because they have underlying health problems that cause them to sleep longer.
The authors of the study published Dec. 5 in the European Heart Journal also found that daytime napping was associated with an increased risk of heart disease and death among those who slept more than six hours a night, but not among those who got less sleep.
"Even though the findings were very interesting they don't prove cause and effect," Julie Ward, a senior cardiac nurse at the British Heart Foundation, who was not involved in the study, told CNN>.
"It's not that long sleep causes death or ill health," but that poor health causes an increase in sleep, Francesco Cappuccio, professor of cardiovascular medicine and epidemiology, Warwick University, U.K., told CNN. He was not involved in the study.