London, Feb 26 (IANS): In yet another instance of how too much of a good thing can be bad for you, new research shows that people who sleep more than eight hours a night face increased risk of stroke.

Long sleepers -- those who sleep more than eight hours a night -- are 46 percent more likely to have a stroke than people who sleep six to eight hours a night, which is considered an average amount of sleep, the findings showed.

"We do not know yet whether long sleep is a cause, consequence or early marker of ill health," said study author Yue Leng from the University of Cambridge in Britain.

The study involved 9,692 people with an average age of 62 who had never had a stroke. They were asked about their sleeping habits once and then again about four years later. The participants were followed for an average of 9.5 years. During that time, 346 people had a stroke.

Of the 986 people, who slept more than eight hours a night, 52 had a stroke, compared to 211 of the 6,684 people who slept an average amount. People who shifted over time from sleeping less than six hours a night to sleeping more than eight hours a night were nearly four times as likely to have a stroke as people, who consistently slept an average amount.

The relationship between long sleep and stroke stayed the same after researchers accounted for factors such as high cholesterol, high blood pressure, body mass index and physical activity.

The study appeared in the journal Neurology.