PhotoIn the 19th century people often went to bed when the sun went down and rose before dawn. After all, there was no TV to watch or web to surf.

Besides, it was thought that every hour of sleep you got before midnight was worth 2 hours of sleep after that hour. Modern research suggests there might be some truth in that.

Korean researchers writing in the Endocrine Society’s Journal of Clinical Endocrinology & Metabolismhave concluded that people who stay up late are more likely to develop diabetes, metabolic syndrome and sarcopenia than people who turn in early, even when they get the same amount of sleep.

Sleep-wake cycle

The study focused on a person’s natural sleep-wake cycle. It found that staying awake later at night is likely to reduce the amount and quality of sleep. Maybe even more important, it connected staying up late with strange dietary patterns, with subjects tending to eat the wrong kinds of food at the wrong times.

“Regardless of lifestyle, people who stayed up late faced a higher risk of developing health problems like diabetes or reduced muscle mass than those who were early risers,” said Nan Hee Kim, of Korea University College of Medicine in Ansan, Korea and one of the study’s authors. “This could be caused by night owls’ tendency to have poorer sleep quality and to engage in unhealthy behaviors like smoking, late-night eating and a sedentary lifestyle.”

Night owls less healthy

In the study, some subjects stayed up late and others went to bed early. Even though the people who stayed up late were younger, they had higher levels of body fat and triglycerides, or fats in the blood, than the older subjects who both turned in and rose early.

The night owls also were more likely to have sarcopenia. That’s  a condition where the body gradually loses muscle mass. Late night men were more likely have diabetes or sarcopenia while late night women tended to have more belly fat and a significant risk of metabolic syndrome.

“Considering many younger people are evening chronotypes, the metabolic risk associated with their circadian preference is an important health issue that needs to be addressed,” Kim said.

The Korean study adds to the growing body of research stressing the importance of sleep to health.

Other research

 “Sleep affects almost every tissue in our bodies,” said Dr. Michael Twery, a sleep expert at the National Institutes of Health (NIH). “It affects growth and stress hormones, our immune system, appetite, breathing, blood pressure and cardiovascular health.”

According to NIH, a good night’s sleep consists of 4 to 5 sleep cycles. Each cycle includes periods of deep sleep and rapid eye movement (REM) sleep. It’s during that time that you have dreams.

“As the night goes on, the portion of that cycle that is in REM sleep increases. It turns out that this pattern of cycling and progression is critical to the biology of sleep,” Twery said.

How much sleep do you need? It will vary by age but Twery says – in addition to the number of hours – the quality of the sleep is just as important.

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