

By Sam Downing|

How to tell if you're not getting the right amount


Those conditions are high waist circumference, which suggests excess fat stored around the abdomen; high blood pressure; high blood triglycerides (aka fat); high blood glucose (sugar); and low HDL "good" cholesterol. If you have three or more, you're deemed to have metabolic syndrome.

There are a number of factors that influence your likelihood of developing metabolic syndrome, including what you eat, how much you weigh and how much physical activity you do. In a new study published in BMC Public Health, Korean researchers sought to understand what effect sleep also has.

They determined that fewer than six hours of sleep a night and more than 10 is linked to metabolic syndrome and the conditions that fuel it, and that the effects vary by sex.

"We observed a potential gender difference between sleep duration and metabolic syndrome, with an association between metabolic syndrome and long sleep in women and metabolic syndrome and short sleep in men," said Claire E. Kim, a researcher from Seoul National University College of Medicine and lead author of the study, in a statement.

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The team pored over data collected over 10 years from more than 130,000 men and women from Korea, where about a third of adults have metabolic syndrome — about the same percentage as Australia.

Men who habitually slept fewer than six hours every 24 hours proved more likely to have metabolic syndrome and higher waist circumferences, while women who slept for that duration were more likely to have higher waist circumferences.

Men who slept more than 10 hours were more likely to have metabolic syndrome and high blood triglycerides. Women who slept more than 10 hours were more likely to have metabolic syndrome, higher waist circumferences, high blood triglycerides and blood sugar, and low HDL cholesterol.

On average, adults are recommended to aim for seven to nine hours of sleep per night. According to the data, sleeping too little was about 10 times more common (affecting around 12 percent of study participants) than sleeping too much.


The study only observed a link between self-reported sleep duration and metabolic syndrome and its components — not that sleep directly causes either.

It's not yet clear why sleep duration might be linked to metabolic syndrome, although the paper suggested a couple of biological explanations: too little sleep may upset the hunger hormones ghrelin and leptin, spurring you to eat more; impair glycemic control, increasing the odds of high blood pressure and diabetes; or increase the stress hormone cortisol, putting a strain on your body.

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