People need 6–8 hour daily sleep to ensure health

While it is unhealthy to sleep too little, it is also a problem to sleep for too long. One out of 10 South Koreans has health problems due to insufficient sleep, while one to two in 100 people have problems because they sleep too much. This is the outcome of the largest ever epidemiological study that was conducted in 130,000 middle-aged South Koreans. That is, if people do not get an appropriate amount of sleep, the probability for them to develop various metabolic syndromes (phenomena involving such illnesses as high blood pressure and diabetes) including obesity increases significantly. The appropriate sleeping hours that would not hamper health is found to be six to eight hours per day.

A research team led by Prof. Kang Dae-hee at Seoul National University College of Medicine’s preventive medicine department analyzed sleeping hours among 133,608 men and women aged 40 to 69, and published their findings in the journal “BMC Public Health” on Wednesday. The team analyzed correlates between health indicators, such as blood cholesterol levels and blood sugar levels, and their sleep hours. The results showed that men who sleep less than six hours stand a 15 percent higher chance to see their waist measurement exceed 90 centimeters than men who sleep six to eight hours, and a 12 percent higher chance to suffer from metabolic syndromes. Women who sleep less than six hours a day also stood a 9 percent higher chance to see their waist measurement gain.

Sleeping too long also entailed problems. Among those who took part in the study, 1.5 percent of men and 1.7 percent of women were found to sleep 10 hours or more per day. Males who sleep 10 hours or more saw the risk of metabolic syndrome and rising neutral fat levels in the blood increase 28 percent to 33 percent. Females who sleep too long saw the risk of a rising metabolic syndrome gain 40 percent, and the risk of growing waist measurement jump 39 percent to 41 percent. The level of HDL-C dubbed “good cholesterol” declined.

“South Korea is a country where the ratio (morbidity) of people suffering from metabolic syndrome is high,” said Claire Kim, a lead author of the study and researcher at the Seoul National University College of Medicine. “We need to find elements that can be improved such as sleeping hours.”


ashilla@donga.com