Let’s continue on the topic of napping.

We left off discussing some of the negative aspects of napping.  We were reviewing the concept of sleep inertia and how if a nap is too long, a person might have a reduction in performance and worsened mood soon after waking.  Obviously this usually is counterproductive to the reasons why we take a nap in the first place, so it is best to limit naps to less than 30 minutes.  Sleeping longer than this can cause a person to wake up in the deeper stages of non-REM sleep, which will make sleep inertia worse.  Alternatively, if you have the time, you can sleep for 90-120 minutes, which is the approximately the amount of time it takes to complete a cycle of non-REM and REM sleep and may also allow one to wake up more invigorated.

Another concern about daytime naps is that they could lessen the quality of sleep on the night following the nap.  While this theory may be based on real world observation, researchers have not really been able to find evidence to support this premise.  In fact, in one study of healthy adults aged 55-85 given a two hour nap opportunity, not only was there no worsening of sleep on the night following the nap (so they basically increased their total sleep time by 2 hours), but there was improved physical and mental performance in the nap group after the nap and even on the following day.

About a year ago a large study out of Greece was published and was widely reported in the media.  It is known that in areas where the siesta is a common practice, there tends to be a lower frequency of coronary heart disease (CHD).  Previous studies had shown conflicting results as to whether or not the siesta could be given credit for some of the lower heart disease risk, or was perhaps a marker of increased risk of heart disease.  Why would the siesta be a potential cause of heart disease?  There are two reasons: firstly, people who sleep in the afternoon tend to have lower levels of physical activity, which of course is a marker of increased CHD risk.  Additionally, people with serious health conditions including stroke, CHD, and diabetes tend to take daily naps- while also being at increased risk of CHD. 

This well designed study helped to put many of these questions to rest (so to speak).  The authors actually found that in men who were still working the risk of death from CHD was significantly lower.  The likely reason for this is that an afternoon siesta in healthy individual can act as a “stress-releasing” habit.  It is well known that stress can have both short and long term adverse effect on heart health.  In the unemployed (or retired) male population there was little evidence of this benefit, possibly due to lower levels of physical activity and worse general health status.  (There were too few heart-related events in women to make any conclusions).