ATHENS, Greece -- Greek men and women who took a midday nap at least occasionally had a 12% lower risk of coronary mortality, according to a study here, and those who napped for at least three times per week did three times as well.
ATHENS, Greece, Feb. 12 -- A midday snooze may be just the ticket for reducing risk of death from coronary heart disease, reported researchers here.
Among more than 23,000 Greek men and women, those who napped at least occasionally had a 12% lower risk of coronary mortality, and those who napped for more than 30 minutes at least three times per week had a 37% lower risk of death, reported Androniki Naska, Ph.D., of the University of Athens Medical School, and colleagues.
Working men, who are presumably under stress, got more of a benefit from 40 winks than men of leisure, the investigators wrote in the Feb.12 issue of the Archives of Internal Medicine.
The Mediterranean custom of sleeping away the hottest part of the day has long been cited as a possible explanation for the lower incidence of heart disease in the region, along with the low-fat, high fiber Mediterranean diet and red wine.
"Two case-control studies in Greece provided weak evidence in support of this hypothesis, and triggered another considerably larger case-control study in Costa Rica, as well as a number of inherently superior cohort investigations of this issue," Dr. Naska and colleague wrote.
Those studies, some of which used daytime sleepiness as a surrogate for napping, did not find that more midday sleep was conducive to heart health. In fact, the researchers in the Costa Rica study found evidence that daily siestas are associated with increased risk for myocardial infarctions.
But the earlier studies did not adequately assess the potentially protective role that siestas might play, the Greek investigators asserted.
They conducted a population-based cohort study using data from the Greek cohort in the European Prospective Investigation into Cancer and Nutrition (EPIC) study. The participants were enrolled from 1994 through 1999, and follow-up occurred through the end of 2005.
The Greek cohort had 23,681 men and women who at enrollment had no history of coronary heart disease, stroke, or cancer. At baseline, participants reported whether they took midday naps, and if so, the average duration (in five-minute increments) of their naps, as well as the weekly frequency.
The authors classified participants as never nappers, systematic nappers (at least three times per week with an average nap duration of at 30 minutes per nap, and occasional nappers (either once or twice per week, frequently on weekends, or short midday naps with average duration of less than 30 minutes, irrespective of the weekly frequency).
Study participants also reported their work-related and leisure-time participation in physical activities. Each activity was measured in multiples of resting metabolic rate.
The authors created Cox regression models using time to coronary death, with deaths from other causes censoring events.
They found that compared with never-nappers and after controlling for potential confounders such as age, smoking status, and body mass index, men and women who took a siesta of any frequency or duration had a coronary mortality ratio of 0.66 (95% confidence interval 0.45-0.97).
The mortality ratio for occasional nappers was 12% lower than that of the perpetually wakeful group (0.88; 95% CI, 0.48-1.60), while systematic nappers had a 37% lower coronary mortality (mortality ratio 0.63; 95% CI, 0.42-0.93).
"Among men, the inverse association was stronger when the analysis was restricted to those who were currently working at enrollment, whereas among women, a similar analysis was not possible because of the small number of deaths," the authors noted.
The findings suggest that among healthy working men, siestas may help to alleviate stress, they suggested.
They noted that their results may be limited by the relatively small number of fatal coronary events (85 among men, and 48 among women), and by the relatively short follow-up.