Taking a nap in the middle of the day has many benefits. I have posted here about some of those benefits and about some of the famous people who napped. Now we also have specific evidence that it has significant health benefits, thanks to a recent study by the European Society for Cardiology.
The study showed that naps can significantly reduce blood pressure levels. High blood pressure, otherwise known as hypertension, is widespread in the West, especially for older people. It's known as 'the silent killer' because it produces no obvious symptoms of itself; and yet it is a major risk factor for strokes and heart attacks.
"Noon sleep seems to have beneficial effects,"said the author of the new study, cardiologist Dr Manolis Kallistratos.
"Midday naps seem to lower blood pressure levels and may probably also decrease the number of required antihypertensive medications."
By the way, you'll note that he used the words 'noon' and 'midday'. That seems very specific; but it's possible that something was lost in translation and he simply meant 'in the middle of the day'. Previous writers on sleep science (admittedly not cardiologists) believed that the optimum time for a nap varies according to what benefits you want to get out of it, and what time you got up. But I suspect they were not qualified to comment on this very specific health aspect.
Dr Kallistratos said:
"two influential British Prime Ministers were supporters of the midday nap. Winston Churchill said that we must sleep sometime between lunch and dinner, while Margaret Thatcher didn't want to be disturbed at around 3:00 pm. According to our study, they were right."
(Baroness Thatcher famously slept only three or four hours at night; I hadn't previously realised that she liked to nap in the afternoon.)
The study assessed the effect of naps on blood pressure (BP) levels in 386 middle-aged patients (200 men and 186 women with an average age of 61.4), all with hypertension. Choosing a group who were all already hypertensive is by no means unrepresentative: to see how widespread hypertension is among middle-aged and older people, at least in the West, this 2012 article is instructive. It was written by a Guardian journalist, who'd had healthily low blood pressure until his early 40s, but then found himself hypertensive at age 47, with a BP of 150/95 mmHg, which was described to him as being
"well above the risk threshold".
Back to Dr Kallistratos's study. After adjusting for other factors that could influence BP such as age, gender, BMI, smoking status, salt, alcohol, exercise and coffee, the researchers found that midday sleepers had 5% lower average 24 hour ambulatory systolic BP (that's equivalent to a drop of 6 mmHg in the first of those two numbers by which BP is always expressed) compared to patients who did not nap. Their average systolic BP readings were 4% lower when they were awake (5 mmHg) and 6% lower while they slept at night (7 mmHg) than non-nappers.
Dr Kallistratos said:
"Although the mean BP decrease seems low, it has to be mentioned that reductions as small as 2 mmHg in systolic blood pressure can reduce the risk of cardiovascular events by up to 10%."
My inference is that the significant reductions in BP that he observed could reduce the risk of heart attacks and strokes by well in excess of 10%. That's remarkable.
Longer naps better than shorter ones?
The study's authors also said that the duration of midday sleep had a significant effect on the extent of BP reductions. Yes, patients who slept for 60 minutes midday had lower blood pressure readings (averaged over 24 hours) than patients who did not nap; but longer sleeps were even more beneficial.
What exactly was meant by 'longer' was not specified in the report. However, speaking as a convinced and regular napper, I would be happy to participate in further research.
Want to know more?
My earlier post Napping: the celebrity fans, the benefits, the practicalities, on my Huffington Post archive.