Washington D.C.: A new study has linked long naps and daytime sleepiness to greater risk of metabolic syndrome.
Specifically, napping for 40 minutes or longer was associated with a steep increase in the risk of developing metabolic syndrome, a collection of health conditions such as high blood pressure, high cholesterol, excess fat around the waist and high blood sugar that all increase a person's risk for heart disease.
Being overtired during the day was also associated with an increased risk of metabolic syndrome.
"Taking naps is widely prevalent around the world," said lead author Tomohide Yamada from the University of Tokyo, adding "So, clarifying the relationship between naps and metabolic disease might offer a new strategy of treatment, especially as metabolic disease has been increasing steadily all over the world."
This meta-analysis evaluated data from 21 observational studies involving 307,237 Asian and Western subjects and builds on previous work by Yamada and his colleagues that tied lengthy naps and daytime sleepiness to a greater prevalence of heart disease and type-2 diabetes. This study is the group's largest analysis to date of data collected from a number of countries.
The results showed a J-shaped relationship between time spent napping and metabolic syndrome risk. Subjects who napped for less than 40 minutes did not show any increased risk for metabolic syndrome, but beyond 40 minutes, risk sharply rose. Napping for 90 minutes appeared to increase metabolic syndrome risk by as much as 50 percent, as did being excessively tired during the day. Interestingly, there was a slight dip or decrease in the risk of metabolic syndrome among those napping less than 30 minutes.
"Sleep is an important component of our healthy lifestyle, as well as diet and exercise," Yamada said. "Short naps might have a beneficial effect on our health, but we don't yet know the strength of that effect or the mechanism by which it works."
The study is scheduled for presentation at the American College of Cardiology's 65th Annual Scientific Session....