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像良好的饮食和运动一样，睡眠是整体健康的关键组成部分。当前的睡眠准则建议年龄在26至64岁的睡眠每晚7-8个小时的成年人，并练习健康的睡眠卫生，包括将白天的午睡限制在30分钟，避免刺激剂，例如咖啡因和能量饮料，并避免睡前，避免繁重或丰富的食物睡觉前。

Previous research has shown that insufficient as well as excessive sleep are associated with health-related conditions such as hypertension, obesity, diabetes, cardiovascular events or mortality and stroke.

Metabolic syndrome, which is highly prevalent in Korea, is defined as a metabolic disorder consisting of at least three of the following: elevated waist circumference, high triglyceride levels, low high-density ‘good’ cholesterol levels (HDL-C), hypertension and high fasting glucose.

Researchers at Seoul National University College of Medicine have carried out the largest study examining a dose-response relationship between sleep duration and metabolic syndrome and its components in 133,608 Korean men and women aged 40-69 years. To do this, they used data from the HEXA study, a large-scale community-based study conducted in Korea during the years 2004-2013, which included information on socio-demographic characteristics, medical history, medication use, family history, lifestyle factors, diet, physical activity, and reproductive factors for women.

Sleep duration was assessed by asking the question: “In the past year, on average, how many hours/minutes of sleep (including daytime naps) did you take per day?”

The study, published today inBMC Public Health, finds that compared to individuals who sleep six to seven hours per day, men who sleep fewer than six hours are more likely to have metabolic syndrome and higher waist circumference. Women who sleep fewer than six hours are more likely to have higher waist circumference. Furthermore, sleeping more than ten hours per day was associated with metabolic syndrome and increased levels of triglycerides in men, and with metabolic syndrome, higher waist circumference, higher levels of triglycerides and blood sugar, as well as low HDL-C in women.

The exact mechanisms for the gender differences observed are unclear but a possible explanation is that women experiencing menopausal transition face erratic fluctuations and eventual decline in estrogens as well as ovarian estradiol which may lead to frequent sleep disruptions, a common characteristic of long sleep duration. Another theory is that women may have shorter circadian periods which contributes to higher insomnia.

睡眠持续时间和代谢综合征之间关联的基础的生物学机制也尚不清楚，但潜在的因素包括增加食欲和热量摄入量或减少每天睡眠不到七个小时的人的能量消耗的荷尔蒙水平，这可能会导致腰部增加肥胖的周长和发展。

重要的是要注意，这项研究的横截面，观察性质不允许对因果关系得出结论。睡眠持续时间的估计是基于自我报告数据而不是客观的措施，可能反映了“床上的时间”，实际上花费的时间或人们认为他们睡觉的时间。同样，由于该研究没有区分白天的午睡和夜间睡眠，因此无法分别评估它们对健康的影响。