CAMBRIDGE – The National Sleep Foundation among thousands of medical doctors worldwide have already recommended a minimum of 8 hours sleep for normal adults, but a new study published by researchers from the University of Cambridge now suggests that sleeping for more than 8 hours increases your chances for developing stroke by 46%; and incidentally, sleeping anything less than 8 hours also predisposes you to risks of stroke by 15%.


Contrary to the National Sleep Foundation’s recommendation of an average of 7-9 hours of sleep per night for adults aged 18-64 years, the University of Cambridge researchers present a different concept. According to them, they monitored close to 10,000 adults over a 10-year period, and found that 346 developed stroke within this period. Taking their age and gender into account, the researchers found that amount of sleep affected their chances of having strokes.

They found that people that sleep for over 8 hours have an increased risk for having stroke, and those that sleep for lesser than 6 hours also have tendency for having stroke. From those surveyed, 7 out of 10 reported they slept between 6-8 hours every day, and 10% said they slept for over 8 hours every day.

While the researchers have a difficult proving why too much sleep can lead to stroke, poor sleep has often been blamed for health risks and disorders because of its potential for raising cortisol levels, leading to higher blood pressure and complications that tend to stroke.

According to Dr. Alberto Ramos of the University of Miami’s Miller School of Medicine, and James Gangwisch of Columbia University, “Long sleep duration could therefore be a harbinger of stoke through its association with potent cardiovascular risk factors. Lengthening sleep duration could portend strokes and serve as an early warning sign, suggesting the need for further diagnostic testing or for taking precautionary measures.”

However, Dr. Madina Kara, a research manager at the Stroke Association, notes that the study did not prove poor sleep can cause stroke, saying, “The known risk factors (for stroke) include high blood pressure, smoking and lack of exercise. Eating healthily, getting active and quitting smoking can make a big difference in reducing your risk of stroke.”

Yue Leng, a PhD candidate at the University of Cambridge, pointed out that “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. 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.”

Experts still maintain that it is still better to maintain an average of 8 hours of sleep per night to prevent any risks to cardiovascular health.

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