Napping Once Or Twice A Week Might Be Good For Your Heart Health – But Scientists Are Not Sure Why

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In what might just be the best news of the week (admittedly, it's only Tuesday), napping has been linked to a reduced risk of heart attack and stroke by scientists at the University Hospital of Lausanne in Switzerland.

According to a paper published in the journal Heart, study participants who indulged in a siesta once or twice a week were 48 percent less likely to have a heart attack, stroke or experience heart failure over a five-year-period compared to those that did not nap at all. But we shouldn't jump to too many conclusions just yet – as the researchers themselves have been quick to point out, the results reveal an interesting correlation but do not show a cause and effect. There may be a third, confounding factor in the works.

Previous studies examining napping's effect on heart health have generated a mixed bag of results. One Greek study linked siesta to lower coronary mortality. Another, also Greek, to a lower risk of coronary heart disease. Others have found no significant link at all, while still more suggest that it can, in fact, increase the risk of cardiovascular disease and various cardiac events.

And so, to try and clarify the health impacts of napping by addressing certain discrepancies in previous studies (e.g. considering napping frequency), researchers compared napping frequency, average nap duration, and the risk of cardiovascular disease events (fatal and non-fatal) over a five-year period. The experiment involved 3,462 healthy participants – all randomly selected residents from Lausanne – aged 35 to 75. 

The number of naps taken the previous week varied from none at all (58 percent) to six to seven (11 percent). A little under one in five (19 percent) took one to two naps. Another 12 percent took three to five. Over the course of the research, there were 155 cardiovascular events.

The researchers found the ideal napping rate appears to be one to two times a week. Participants who fell into that category saw their risk of experiencing a cardiovascular disease event decrease 48 percent – even when factors such as age, night-time sleep duration, and health aspects (e.g. high blood pressure) were taken into consideration. The length of the nap did not seem to matter. The only factors that did seem to have an effect were age (65+) and severe sleep apnoea. 

"While the exact physiological pathways linking daytime napping to [cardiovascular disease] risk is not clear, [this research] contributes to the ongoing debate on the health implications of napping, and suggests that it might not only be the duration, but also the frequency that matters," Yue Leng and Kristine Yaffe from the University of Calfornia at San Francisco said in a linked editorial.

And while there was originally a 67 percent increased risk of a cardiovascular disease event in the frequent napper contingent, this pretty much disappeared to nil when other factors (such as age, educational status, BMI, and various health conditions) were taken into consideration.

Although interesting, the study doesn't necessarily provide the conclusive proof you might need to lobby your employer for a nap room. As the researchers point out, there may be third factors at play. There is also the problem that the study relies on self-reporting, which is not always the most accurate and fool-proof method.

Naveed Sattar, a professor of metabolic medicine at the University of Glasgow who was not involved in the study, said the results were "somewhat interesting" but added the differential risks may be more reflective of the infrequent nappers healthier lifestyles or organized lives than the napping itself.  

"I don’t think one can work out from this work whether “intentional” napping on one or two days per week improves heart health so no one should take from this that napping is a way to lessen their heart attack risk – to prove that would require proper trials," Sattar said in a statement.

"For now, far better to aim for regular good night’s sleeps and to follow usual lifestyle advice of good diets and decent activity levels."

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