Napping for 40 minutes or longer during the day, along with daytime sleepiness, may be associated with an elevated risk of developing metabolic syndrome, according to research published March 23 which will be presented at ACC.16 in Chicago.

The study, led by Tomohide Yamada, MD, PhD, et al., analyzed data from 21 observational studies involving 307,237 Asian and Western subjects who self-reported their daytime tiredness and napping habits. Researchers compared the participants’ responses to their history of metabolic syndrome, type-2 diabetes and obesity.

The analysis revealed that subjects who napped for more than 40 minutes during the day showed a sharp increase in the risk of metabolic syndrome. Napping for 90 minutes appeared to increase the risk by as much as 50 percent, as did excessive daytime tiredness. The study also showed a slight decrease in risk of metabolic syndrome when participants napped for less than 30 minutes. Previous work by Yamada and his team showed that napping for longer than one hour corresponded to a 50 percent increase in type-2 diabetes.

The authors note that as the data was dependent on self-reporting by participants, the study’s findings may not be representative of the world population. However, the results indicate a need for further study into how sleep habits influence metabolic syndrome and cardiovascular disease, especially considering that nap length appears to influence risk both upward and downward.

Moving forward, future research should focus on “clarifying the relationship between naps and metabolic disease,” with the hope of offering a new strategy of treatment, says Yamada.

“Excessive weight and its associated increased risk for sleep apnea might be a potential mechanistic pathway to explain these results,” adds Kim A. Eagle, MD, MACC, editor-in-chief of ACC.org.

Keywords: Cardiovascular Diseases, Diabetes Mellitus, Type 2, Habits, Metabolic Syndrome, Obesity, Self Report, Sleep, Sleep Stages, ACC Annual Scientific Session

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