People who get less than six hours of sleep a night may be more likely to have risk factors that increase their odds of diabetes, heart disease and strokes, a Korean study suggests.
This combination of risk factors - including high blood sugar, high cholesterol, extra fat around the midsection, high blood pressure and excess amounts of fats in the blood - is known as metabolic syndrome.
"The 'short' sleepers should be aware of the risks of developing metabolic syndrome, which could lead them to suffer from life threatening and chronic diseases," lead author Dr. Jang Young Kim of Yonsei University in South Korea said by email.
Kim's team followed about 2,600 adults for more than two years and found that participants who didn't get at least six hours of sleep a night were 41 percent more likely to develop metabolic syndrome than individuals who got six to eight hours of shuteye.
The findings are drawn from two lifestyle surveys that included questions about sleep habits. The surveys were administered once between 2005 and 2008 and again sometime between 2008 and 2011. Study participants also underwent medical exams and shared their medical history.
After an average follow-up of 2.6 years, about 560 people in the study, or 22 percent of participants, developed metabolic syndrome, according to the results in the journal Sleep.
Short sleep duration was linked to about 30 percent increased risk of high blood sugar and excess belly fat, as well as 56 percent higher odds of hypertension, compared to those who slept longer.
One shortcoming of the study is its reliance on participants to accurately recall and report on their sleep habits, medical conditions and lifestyle behaviors, the authors acknowledge. It also lacked data on the quality of sleep.
Still, the findings are consistent with other studies that have found an association between sleep duration, cardiovascular disease and metabolic syndrome, said Kristen Knutson, a sleep researcher at the University of Chicago who wasn't involved in the study.
"The strength of this study is that it is a prospective study, which means short sleep was associated with the development of metabolic syndrome," Knutson said by email. "This is important because the sleep duration was measured before the people had the disease."
To avoid the ill effects of insufficient sleep, patients should take a close look at their daily routines and make sure they allow enough time in their schedule for rest, Knutson said. Some things like time for work, school or childcare may not be optional, but other things like time for television or movies might be replaced with more rest.
"We don't know yet if it is possible to reverse the effects" of too little sleep, Knutson added. "Still, adopting a healthy lifestyle which includes appropriate sleep, a healthy diet and sufficient exercise will be beneficial to your health."