Many believe that lying down to take a nap is a harmless activity. But now scientists show that dozing for more than an hour can be risky.
“Daytime napping is common around the world and generally considered a healthy habit,” said study author Dr. Zhe Pan of Guangzhou Medical University, China. “A common belief is that napping improves performance and counteracts the negative effects of 'sleep debt'. Our study challenges these widely held opinions.”
Previous research on the link between daytime naps and death or cardiovascular disease has shown conflicting results. In addition, it did not take into account the duration of nighttime sleep.
This study summarizes the available evidence to assess the relationship between napping and the risks of all-cause death and cardiovascular disease. A total of 313,651 participants from more than 20 studies were included in the analysis. About 39% of the participants took a nap.
The analysis found that long naps (more than 60 minutes) were associated with a 30% greater risk of all-cause death and 34% greater risk of cardiovascular disease compared to not napping. When nighttime sleep was taken into account, long naps were only associated with an increased risk of death in those who slept more than six hours a night.
Overall, naps of any length were associated with a 19% increased risk of death. The association was more pronounced in women, who had a 22% greater chance of death with napping compared to no-napping, and older participants, whose risk increased by 17% with napping.
Short naps (less than 60 minutes) were not risky for developing cardiovascular disease. dr. Pan said:"The results suggest that shorter naps (particularly those of less than 30 to 45 minutes) may improve heart health in people who don't get enough sleep at night."
The reasons why napping affects the body are still uncertain, said Dr. Pan, but some research has suggested that long snooze is linked to higher levels of inflammation, which is risky for heart health and longevity. Other research has linked napping to high blood pressure, diabetes and poor overall physical health.
He concluded:“If you want to have a siesta, our study shows that it is safest to have it under an hour. For those of us who are not in the habit of sleeping during the day, there is no convincing evidence to begin with.”
