Nap, Just Not for Too Long

Napping isn’t a bad thing…as long as it’s not for more than 30 minutes, at least according to the latest research presented at the American College of Cardiology’s 64th annual Scientific Session in Chicago, Illinois. Researchers from the University of Tokyo discovered that naps of 40 minutes or longer significantly increase your risk of metabolic disease.

How Metabolic Disease and Napping Relate 

Cat-nap on a sofa. An elegant brunette woman napping on a sofa in a loft, curling her hands under her chin. Urban chic ambiance.

Metabolic disease is characterized by the following symptoms:

  • High blood pressure
  • Excess fat around the belly and waist
  • High blood sugar

…all of which significantly increase a person’s risk for developing cardiovascular disease.

In 2015, researchers demonstrated a link between 60-minute naps and an 82% increase in heart disease and a 27% greater risk of death from all causes. People who napped longer than 60 minutes were 46% more likely to develop diabetes, and people who reported feeling overly tired during the day had a 56% higher risk for diabetes. Naps of less than 30 minutes, however, moderated this disease risk.

For this latest study, Japanese researchers conducted a meta-analysis of 21 studies comprised of 307,237 people from Asia and the West. Types of questions answered included:

  • Do you have a problem with sleepiness during the day?
  • Do you take a daytime nap?
  • Do you sleep during the day?

They compared the responses with the volunteers’ history of metabolic syndrome, type 2 diabetes, and obesity. Results indicated that people who napped for less than 40 minutes were at no higher risk for metabolic syndrome, but when people napped for more than 40 minutes, the probability of developing metabolic syndrome increased exponentially.

Napping for 1.5 hours was equivalent to a 50% higher risk for metabolic syndrome, while napping for less than 30 minutes decreased that risk.

Dr. Tomohide Yamada, PhD, a diabetologist at the University of Tokyo in Japan, explains: “Sleep is an important component of our healthy lifestyle, as well as diet and exercise. 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.”

When it comes to napping, experts recommend following the guidance of the National Sleep Foundation—20 to 30 minute naps seem to be the sweet spot.