Last updated June 14, 2018 at 2:30 pm
Korean study suggests 6-10 hours is best.
Getting too much sleep or not enough may affect your health and waist line, according to new research.
A study of 133,600 Koreans suggests fewer than six or more than 10 hours of sleep per night is associated with an increased risk of metabolic syndrome, which is characterised by having a fat waist, high blood-fat levels, low levels of good cholesterol, high blood pressure and high blood sugar.
However, the researchers, from Seoul National University College of Medicine, stress that their study does not show that abnormal sleep actually causes metabolic syndrome. How that link might work remains unclear.
Of those studied – all aged 40 to 69 – nearly 11 per cent of men and 13 per cent of women slept fewer than six hours, while 1.5 per cent of men and 1.7 per cent of women slept more than 10 hours.
Men who slept fewer than six hours were more likely to have metabolic syndrome and higher waist circumference. Women were more likely to have higher waist circumference.
Sleeping more than 10 hours 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 levels of good cholesterol (HDL-C) in women.
Metabolic syndrome in 1 in 4 cases
The prevalence of metabolic syndrome was just over 29 per cent in men and 24.5 per cent in women. The researchers suggest that as the prevalence of metabolic syndrome in Korea is high, it is critical to identify modifiable risk factors such as sleep duration.
“This is the largest study examining a dose-response association between sleep duration and metabolic syndrome and its components separately for men and women,” said lead author Claire E. Kim. “Because we were able to expand the sample of our previous study, we were able to detect associations between sleep and metabolic syndrome that were unnoticed before.”
The researchers used data from the HEXA study, a large, community-based study conducted in Korea from 2004 to 2013. This included information on socio-demographic characteristics, medical history, medication use, family history, lifestyle factors, diet, physical activity, and reproductive factors for women.
Although the biological mechanisms that underlie the association between sleep duration and metabolic syndrome remain unclear, several potential processes have been reported. These include elevated levels of hormones which increase appetite and caloric intake or reduce energy expenditure in people who sleep fewer than seven hours per day, which may lead to increased waist circumference and development of obesity.
The paper published in BMC Public Health.