This risk doubles for older people who persistently sleep longer than average.
A study at the University of Cambridge followed just under 10,000 people aged 42-18 years of age over a period of nine and a half years.
Almost seven in 10 people said they slept between six and eight hours a day.
One in 10 reported sleeping for over eight hours a day.
The study found that those sleeping longer than eight hours were at a 46pc greater risk than average of stroke.
Those who slept less than six hours were also at risk but this figure was 18pc.
People who persistently slept longer than eight hours were at double the risk of stroke compared to those with a persistent average sleep.
“It’s apparent both from our own participants and the wealth of international data that there’s a link between sleeping longer than average and a greater risk of stroke,” said Yue Leng of the University. “
“What is far less clear, however, is the direction of this link, whether longer sleep is a symptom, an early marker or a cause of cardiovascular problems.”
Lack of sleep has been linked with factors such as disrupted metabolism and raised levels of the ‘stress hormone’ cortisol, all of which may lead to higher blood pressure and increased stroke risk.
However, the current study suggests that the association between longer sleep duration and higher risk of stroke was independent of normal risk factors for cardiovascular disease.
Professor Kay-Tee Khaw, senior author on the study, added: “We need to understand the reasons behind the link between sleep and stroke risk. “What is happening in the body that causes this link?
“With further research, we may find that excessive sleep proves to be an early indicator of increased stroke risk, particularly among older people.”
The study is published in the journal Neurology.