The Siesta The siesta is a, traditional, common practice among many healthy people worldwide although its prevalence is strongly associated with hot, tropical regions between 30° N and S of the equator. In these regions there is some evidence of a genetic predisposition to taking a siesta. The siesta would seem to be an evolutionary adaptation i.e. it is too hot during the heat of the midday sun to be able to act without the need of considerable effort to remain cool, therefore it was easier to find a cool place to sleep thus conserving, what could be very limited, resources. As Noel Coward remarked, in hot climates only ‘mad dogs and Englishmen go out in the midday sun’. This propensity to sleep after midday in hot countries expresses itself as the siesta and in colder climes as the ‘post lunch dip’, a natural drop in cognitive performance, (which does not actually need you to eat food for it to to occur). There is little evidence concerning the taking of a siesta and nocturnal sleep quality. However it seems that subjective perception of nocturnal sleep is undiminished in those that take a siesta. There is evidence that siesta can increase daytime alertness and counteract the effects of sleep deprivation and thus can have a beneficial positive effect on daily work performance. There are mixed messages about the medical benefits of the siesta, for instance there are a few studies that have linked siesta with an increased risk of myocardial infarction. Whilst on the other hand there are other studies which showed a protective action of siesta against coronary artery disease. The difference may be explained by the fact that in some societies a siesta is part of a sedentary lifestyle which is also associated with other risk factors e.g. obesity, diabetes, hypertension which are linked to an increased risk of heart disease, whereas in less sedentary societies the siesta may represent an important stress-coping mechanism that provides protection against coronary artery disease. Therefore if you live in a country that traditionally has a siesta then there is probably little reason for you to stop doing it, but the introduction of the siesta in to more northerly climes really is not going to work, in winter time it will be dark when you wake up and so a mid-afternoon 20 minute ‘power nap’ is probably more appropriate.