Taking a nap during daytime can not only refresh you but also lower the risk of heart attack or stroke if taken once or twice in a week, found a new study.

The impact of napping on heart health has been hotly contested since many of the published studies on the topic have failed to consider napping frequency, or focused purely on cardiovascular disease deaths, or compared regular nappers with those not opting for a mini siesta. In the study published in the Journal 'Heart', researchers looked at the association between napping frequency and average nap duration and the risk of fatal and non-fatal cardiovascular disease 'events,' such as heart attack, stroke, or heart failure, among 3462 randomly selected residents of Lausanne, Switzerland.
 

Each participant was aged between 35 and 75 when recruited between 2003 and 2006 to the CoLaus study. The first check-up took place between 2009 and 2012 when information on their sleep and nap patterns in the previous week was collected, and their health was then subsequently monitored for an average of 5 years. Over half (58 per cent, 2014) of the participants said they didn't nap during the previous week; around one in five (19 per cent, 667) said they took one to two naps; around one in 10 (12 per cent, 411) said they took three to five; while a similar proportion (11 per cent, 370) said they took six to seven.

Frequent nappers (3-7 naps a week) tended to be older, male, smokers, weigh more, and to sleep for longer at night than those who said they didn't nap during the day. And they reported more daytime sleepiness and more severe obstructive sleep apnoea--a condition in which the walls of the throat relax and narrow during sleep, interrupting normal breathing.
During the monitoring period, there were 155 fatal and non-fatal cardiovascular disease 'events'. Occasional napping, once to twice weekly, was associated with an almost halving in attack/stroke/heart failure risk (48 per cent) compared with those who didn't nap at all.

This association held true after taking account of potentially influential factors, such as age, and nighttime sleep duration, as well as other cardiovascular disease risks, such as high blood pressure/cholesterol. And it didn't change after factoring in excessive daytime sleepiness, depression, and regularly sleeping for at least 6 hours a night. Only older age (65+) and severe sleep apnoea affected it. But the 67 per cent heightened cardiovascular risk initially observed for frequent nappers virtually disappeared after taking account of potentially influential factors. And no associations with cardiovascular disease 'events' were found for nap length (from 5 minutes to 1 hour plus).