Sleeping too much or too little linked with increased heart attack risk

New research has found that getting the right amount of sleep may help reduce your risk of a heart attack, even if you have a genetic predisposition to heart disease.

Carried out by researchers at the University of Colorado Boulder along with co-authors at the Massachusetts General Hospital, USA, and the University of Manchester, UK, the new study looked at 461,347 individuals age 40 to 69 who had never had a heart attack and who were taking part in UK Biobank, a large long-term study which includes genomic data on more than half a million UK residents.

The researchers analysed the participants' self-reported sleep habits and medical records and also looked at their genetic information to determine whether those who were genetically predisposed to short sleep were also more likely to have heart attacks.

To make their analysis they used a method called Mendelian randomization, which involves studying genetic variants to see whether certain factors are associated with a higher or lower risk of disease. As it gives more reliable results, any associations found are more likely to suggest a direct relationship.

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Participants were then followed for seven years.

The findings, published on Monday in the Journal of the American College of Cardiology, showed that during the study, those who slept less than six hours were 20 per cent more likely to have a heart attack compared to those who slept six to nine hours per night.

In addition, those who slept more than nine hours each night were 34 per cent more likely to suffer a heart attack.

The more people fell outside this six-to-nine hour range, the more their risk increased. For example, those who slept five hours per night had a 52 per cent higher risk of heart attack than those who slept seven to eight, while those who slept ten hours per night were twice as likely to have one.

The findings also held true after taking into account 30 potentially influencing factors such as body composition, physical activity, socioeconomic status and mental health.

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When the researchers looked only at people with a genetic predisposition to heart disease, they found that sleeping between six and nine hours nightly cut their risk of having a heart attack by 18 per cent.

"This provides some of the strongest proof yet that sleep duration is a key factor when it comes to heart health, and this holds true for everyone," said senior author Celine Vetter.

"It's kind of a hopeful message, that regardless of what your inherited risk for heart attack is, sleeping a healthy amount may cut that risk just like eating a healthy diet, not smoking, and other lifestyle approaches can," added lead author Iyas Daghlas.

"Just as working out and eating healthy can reduce your risk of heart disease, sleep can too," said Vetter.