The next health trend might come out of nursery school instead of the gym: A study of nearly 24,000 people found that those who regularly took midday naps were nearly 40% less likely to die from heart disease than non-nappers.

Researchers suggest that siestas might protect the heart by lowering levels of stress hormones.

Dimitrios Trichopoulos at Harvard School of Public Health in Boston, Massachusetts, US, and colleagues recruited about 24,000 volunteers between the ages of 20 and 86, in Greece, who had no history of heart disease, stroke or cancer. The researchers collected information about the participants' napping habits and followed them for six years, on average.

After controlling for risk factors such as diet and physical activity, Trichopoulos's team found that people who took at least three naps per week lasting 30 minutes or longer had a 37% reduced risk of death from heart disease than their non-napping counterparts.

Stress hormones

Those subjects who occasionally took short naps lasting less than half an hour had a 12% lower risk than people who never napped.

"If the finding holds true, that's an amazing discovery," comments Rajiv Dhand, a researcher at the University of Missouri - Columbia in Missouri, US, who was not involved in the study. The results suggest that taking naps might be just as important to protecting the heart as other measures, he says, including eating right and taking cholesterol-lowering drugs.

The apparent protective effect of these siestas was more pronounced among working individuals than retirees. The researchers suggest that the naps might boost heart health by keeping levels of stress hormone in check.

They add that this potential stress-busting effect might be most pronounced in people burdened by heavy workloads. Previous studies have linked high levels of stress hormones to increased inflammation in the body and damaged blood vessels.

Earlier work has also indicated that taking naps can improve learning and productivity.