Napping twice a week may reduce the risk of stroke, new studies suggest.

Research by Swiss scientists suggests a daytime nap taken once or twice a week may lower the risk of having a heart attack/stroke, but no such association emerged for either greater frequency or duration of naps.

The study used participants aged between 35 and 75, recruited between 2003 and 2006 to the CoLaus study, which has been looking at the factors behind the development of cardiovascular disease.

Participants’ 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.

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 did not 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.

It did not 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. No associations with cardiovascular disease ‘events’ were found for nap length (from 5 minutes to 1 hour plus).

This is an observational study, and as such, cannot establish cause, added to which the information on nap and sleep patterns relied on personal recall.

However, nap frequency may help to explain the differing conclusions reached by researchers about the impact of napping on heart health, suggest the study authors.

The study is accessible here, as is a linked editorial on the science of napping.