A new research has indicated that sleeping over 8 hours a day associated with greater risk of stroke.
The study conducted at University of Cambridge showed that the risk of stroke doubles for older people who persistently sleep longer than average.
Researchers from the Department of Public Health and Primary Care at the University of Cambridge followed just under 10,000 people aged 42-81 years of age from the European Prospective Investigation into Cancer (EPIC)-Norfolk cohort over 9.5 years.
During 1998-2000 and then again four years later, they asked the cohort how many hours on average they slept in a day and whether they generally slept well.
Almost seven out of ten participants reported sleeping between six and eight hours a day, whilst one in ten reported sleeping for over eight hours a day. Participants who slept for less than six hours or more than eight hours were more likely to be older, women and less active.
Over the almost ten year period of the study, 346 participants suffered a stroke, either non-fatal or fatal stroke. After adjusting for various factors including age and sex, the researchers found that people who slept longer than eight hours a day were at a 46 percent greater risk of stroke than average.
People who slept less than six hours a day were at an 18% increased risk, but the small number of people falling in this category meant the association was not statistically significant.
Yue Leng, PhD candidate at the University of Cambridge, said that it was apparent both from their own participants and the wealth of international data that there was a link between sleeping longer than average and a greater risk of stroke and what was far less clear, however, was the direction of this link, whether longer sleep is a symptom, an early marker or a cause of cardiovascular problems.
Professor Kay-Tee Khaw, senior author on the study, added that they need to understand the reasons behind the link between sleep and stroke risk.
The study is published in the journal Neurology.