Siestas' healthy benefits

Medical Matters:What have Winston Churchill, Einstein, Napoleon and Leonardo da Vinci got in common? They were all siesta devotees, who regularly took an afternoon nap. They were also some of the most productive people in history. Churchill famously said: "You must sleep sometime between lunch and dinner. You will accomplish more."

The desire to have an afternoon snooze reflects our circadian rhythms. In every 24 hours, our bodily functions slow down twice: in the morning from 1am-4am and again in the afternoon at 1pm-4pm.

This biological clock controls the rhythms of body temperature and growth hormone, both of which are related to sleep.

Siestas are a feature of life in Mediterranean and Latin American countries. There are striking similarities in napping habits in siesta cultures, according to sleep expert Dr Chris Idzikowski.

"Napping takes place mainly in the afternoon between 2pm and 4pm; the length of the naps range between 1.5 and two hours; and nearly 90 per cent of napping cultures are found at latitudes between 30 degrees north and 30 degrees south - and the more tropical the climate, the greater likelihood that napping occurs," he says.

Another characteristic of those living in Mediterranean cultures is the low level of heart disease they experience compared with those of us living in northern Europe.

While this is usually attributed to a Mediterranean diet based on olive oil, fruit and vegetables, could siestas have a role in reducing mortality from coronary heart disease?

A study just published in the Archives of Internal Medicine suggests that napping may indeed be good for your heart.

Androniki Naska and colleagues, from the University of Athens Medical School in Greece, followed over 23,000 men and women aged 20-86 for six years to see if taking a siesta reduced the risk of death from heart disease.

When they were recruited, none of the patients had any history of heart disease. In addition, the researchers assessed their level of physical activity and dietary habits over the previous year, so that these factors, which themselves influence heart disease risk, were controlled.

Over the six-year period, 133 participants died from heart disease. The researchers found that people who took naps, of any frequency or duration, had a 34 per cent lower risk of dying from heart disease than those who did not. Those who took regular siestas of 30 minutes or more at least three times per week had a 37 per cent lower risk of heart-related death.

But most striking of all was the benefit seen in working men.

The researchers found that those who had a siesta had a 64 per cent lower risk of death from heart disease during the study than working men who did not have a siesta.

However, because there were only six deaths among working women they were unable to assess the benefits or otherwise of napping for female workers.

"We interpret our findings as indicating that among healthy adults, siesta, possibly on account of stress-releasing consequences, may reduce coronary mortality," the authors said.

The fact that the association was stronger in working men, who face job-related stress, than the non-working men supports this hypothesis, they concluded.

Certainly, there is evidence that stress has both short-term and long-term negative effects on the incidence of, and mortality from, coronary heart disease.

So are there other health benefits from taking a nap? One Japanese study found that a post-lunch 15-minute nap improved alertness and logical reasoning in a group of students who had been restricted to four hours' sleep the night before. Those denied an afternoon sleep did poorly in a test of cognitive function, while students who napped were at their best in mid-afternoon.

How much should we sleep during a siesta? The optimum time is probably around 30-40 minutes, while even 10 minutes' shut-eye seems to help. But ultra short sleeps are not without their problems. The most important is sleep inertia - a period of impaired performance that lasts five-20 minutes after waking up. So a siesta may not suit those working in jobs that require an alert mind immediately after waking up.

James Mass, professor of psychology at Cornell University in New York, claims that for every hour of sleep lost at night, we lose one IQ point the following day. He recommends power napping during the day to increase alertness and reduce stress.

In the United States, one major accounting firm has installed napping rooms in the workplace while other companies run courses in the art of the 15-minute siesta.

Now that we have evidence of its health benefits, readers may wish to consider approaching their human resources manager to approve siesta time during the working day.

Not alone will this improve your health and your work life balance, the clinching factor in your argument is the improvement in your productivity that will surely result from a regular afternoon nap.

Dr Muiris Houston is pleased to hear from readers at mhouston@irish-times.ie but regrets he cannot answer individual medical queries.