Getting enough sleep may be a life or death matter for people with a cluster of heart disease and diabetes risk factors.
In a new study from Penn State University, people with the multiple heart disease and diabetes risk factors known as metabolic syndrome were more likely to die of heart disease or stroke than people without the same risks—especially if they failed to get more than six hours of sleep.
For those who got more sleep, the risk of death was more modest.
“If you have several heart disease risk factors, taking care of your sleep and consulting with a clinician if you have insufficient sleep is important if you want to lower your risk of death from heart disease and stroke,” said Julio Fernandez-Mendoza, lead author of the study and an assistant professor at Penn State College of Medicine and sleep psychologist at the Sleep Research & Treatment Center of the Penn State Health Milton S. Hershey Medical Center.
For this study, the cluster of risks included: body mass index higher than 30 and elevated blood pressure, total cholesterol, fasting blood sugar and triglyceride levels.
When people have three or more of these factors, they are said to have metabolic syndrome, a significant health condition that is found in about one-third of adults in the United States, though the percent varies based on several factors, including age, gender, ethnicity and other factors. It raises the risk of heart disease and diabetes more than any of the single factors alone.
“Sleep is an important component of the lifestyle management of heart disease and stroke risk and should be considered as carefully as diet and physical activity,” said Marie-Pierre St-Onge, chair of the panel who reviewed the evidence on sleep and heart disease for the AHA in 2016. “This study shows that the risk of the metabolic syndrome is clearly different based on one’s sleep duration. As doctors receive information from other tests concerning heart disease risk, they should also ask about their patients’ sleep.”
The information in the current study, which is published in the Journal of the American Heart Association, comes from the Penn State Adult Cohort, a group of 1,344 randomly chosen men and women (average age 48.8 years) who agreed to spend one night in a sleep laboratory and undergo multiple other medical tests. Based on the results, nearly 60 percent of the participants were classified with metabolic syndrome.
Compared with people in the reference group without the same cluster of risks, those with metabolic syndrome who clocked more than six hours of sleep time in the lab were 1.49 times more likely to die of stroke during the 16.6-year follow-up period, while those who slept less than six hours in the lab were 2.1 times more likely to die of stroke.
The short sleepers with metabolic syndrome were also 1.99 times more likely to die from cardiovascular disease compared with the reference group.
“This study is important because, even though it can’t prove cause and effect, it is a long-term study and the first using objective data—measuring sleep rather than asking participants how long they usually sleep,” said St-Onge, who is associate professor of nutritional medicine at Columbia University in New York City.
The results are particularly striking because the researchers adjusted for the presence of sleep apnea—sleep interrupted by pauses in breathing that is a known heart disease risk.
“When people have a sleep study in the lab, the results often aren’t seen as very important once sleep apnea is ruled out, but our results show that those with short sleep in the lab are worse off over the long term,” Fernandez-Mendoza said.
The study adds to a growing body of evidence on the importance of sleep for good health.
In 2015, the American Academy of Sleep Medicine and Sleep Research Society jointly recommended that adults get at least seven hours of sleep a night for optimal health, explaining that inadequate sleep is associated with a host of unwelcome effects, including obesity, diabetes, heart disease, stroke, depression, impaired immune function, increased pain, worse functioning, more accidents and earlier death.
In the current study, deaths from all causes—not just heart disease—were also associated with sleeping less in those with the metabolic syndrome.
“We need future clinical trials to determine whether lengthening sleep, in combination with lowering blood pressure and glucose, can improve the prognosis of people with the metabolic syndrome,” said Fernandez-Mendoza.
According to the Centers for Disease Control and Prevention in a 2014 survey, 23 percent of adults in the U.S. reported sleeping an average of only six hours per night, while another 11.8 percent say they regularly clocked five hours or less.
“There are well-established behavioral techniques, such as cognitive behavioral therapy, that can help people improve their sleep. I hope these results will inspire research into what techniques or medications might work best for people with the metabolic syndrome,” Fernandez-Mendoza said.