People who get less than six hours sleep a night are at greater risk of suffering a stroke, a new study suggests.

US researchers monitored more than 5000 people aged between 45 and 65 for three years. Those who got less than six hours shut-eye were most likely to experience symptoms such as numbness or weakness down one side of their body, dizziness, loss of vision or a sudden inability to express themselves verbally or in writing.

Co-author Virginia Howard, a professor of epidemiology, said many people have these symptoms and don't recognise them as a precursor to having a stroke.

"Sleeping habits can exacerbate the potential for these symptoms, which are internationally recognised as putting people at extraordinary risk of subsequent stroke," Prof Howard said.

Participants were divided into five groups according to how many hours a night they slept. They were asked to report their symptoms every six months.


The impact of sleep deprivation was significant, even taking in to account age, weight and other known risks such as high blood pressure, said scientists at the University of Alabama.

A study of hundreds of thousands of people by Warwick University last year also linked lack of sleep to increased incidence of both strokes and heart disease.

But the latest research focuses on the early symptoms of stroke, which are often ignored.

Prof Howard's team will continue monitoring the participants for several more years.

"It will be very interesting to see what the stroke rate is, and whether early detection may have helped," she said.