Recent evidence has linked irregular sleep with obesity and diabetes, and studies find that sleeping too much can be just as bad for cardiovascular (CV) health as sleeping too little.
Today, the American Heart Association (AHA) has issued its first statement on the topic of sleep disorders, which have joined poor diet and lack of exercise as lifestyle red flags that indicate the likelihood of chronic disease. The statement appears in Circulation, the official journal of the AHA.
The authors, led by Marie-Pierre St.-Onge, PhD, recognize that until recently, lack of sleep was not recognized as a contributor to chronic disease. “An increasing number of Americans choose to curtail sleep in favor of other social, leisure, or work-related activities. This has resulted in a decline in average sleep duration over time,” they wrote.
About 50 to 70 million US adults do not get enough sleep or suffer from a sleep disorder, according to the National Heart, Lung, and Blood Institute, part of the National Institutes of Health. The share of Americans who report sleeping fewer than 7 hours a night is increasing; up from 21.6% in 1977 to 29.1% in 2009.
Increases in night shifts and Americans working more than 1 job to make ends meet have contributed to this phenomenon, and a paper by authors at the Harvard School of Public Health found a decade of shift work was associated with a 40% increase in the likelihood of developing diabetes. A separate study among women found that any shift work was associated with a 9% increase in developing the disease. Another study published earlier this year found that men in particular responded poorly to less than optimal hours of sleep.
“We know that short sleep, usually defined as under 7 hours per night, overly long sleep, usually defined as more than 9 hours per night, and sleep disorders may increase some cardiovascular risk factors, but we don’t know if improving sleep quality reduces those risk factors,” said St.-Onge, an associate professor of nutritional medicine at Columbia University, New York.
Because more work is needed in this area, the AHA statement does not recommend a precise amount of sleep for CV wellness. But the statement does detail what is known about the connections between irregular sleep and risk factors such as obesity, type 2 diabetes, heart disease, high blood pressure, arrhythmias, atherosclerosis, and unhealthy levels of triglycerides and cholesterol.
“Since the scientific evidence doesn’t show a specific dose/response relationship between sleep duration and cardiovascular wellness, the American Heart Association cannot offer specific advice on how much sleep is needed to protect people from cardiovascular disease,” St.-Onge said.
Most research thus far has involved the connections between sleep and its effects on diabetes and obesity. “Those are the 2 main conditions in which there are interventions studies that show that risk factors are increased when sleep is altered,” she said.
While studies show that sleep patterns affect food intake, more work is needed on measuring the impact on actual weight. Studies of longer duration might also show whether varying sleep affects cholesterol, triglycerides and inflammatory markers. Better evidence is needed to make stronger links between poor sleep and diabetes, rising blood pressure, and CV disease, she said.
Most research in this area has been observational; thus, links have been established but a cause-and-effect relationship has not been shown. But healthcare providers are still encouraged to ask patients about sleep problems, such as snoring.
And the need for good sleep must be emphasized by physicians—going without sleep should not be glamorized as a sign of toughness or a better work ethic.
“Patients need to be aware that adequate sleep is important, just as being physically active and eating a balanced diet rich in fruits, vegetables, whole grains, lean meat, and fish are important for cardiovascular health,” St-Onge said. “Sleep is another type of ammunition that we can tailor to improve health.”
St-Onge MP, Grandner MA, Brown D, et al. Sleep duration and quality: impact on lifestyle behaviors and cardiometabolic health: a scientific statement from the American Heart Association [published online September 19 2016]. Circulation. 2016; DOI: 10.1161/CIR.0000000000000444.