National University College of Medicine in South Korea warns that sleeping more than 10 hours a night might be worse.

The purpose of the report, published in BMC Public Health (2018; 18 [720]), was to update existing data on links between sleep duration and metabolic syndrome. To accomplish this, researchers analyzed sleep habits and the incidence of metabolic syndrome in 133,608 Koreans aged 40–69. The findings further support the recommendation that, for optimal health, human beings should aim for 6–8 hours of shuteye per night. Sleeping too little or too much can have deleterious effects. Here’s what the study found.

When compared with study participants who slept a standard 6–8 hours, men who slept <6 hours were more likely to have metabolic syndrome and a larger waist circumference. Women who slept <6 hours likewise tended to have a bigger waist size but fared better in relation to metabolic syndrome. Sleeping 10 hours or more was associated with metabolic syndrome and elevated triglycerides in men. Women who slept this long were more likely to have metabolic syndrome, a larger waist size, elevated triglycerides, low HDL cholesterol and elevated fasting glucose.

The study was published in BMC Public Health.