Sleep disorders such as sleep apnea and insomnia may increase the risk factors associated with heart disease.
The statement, published in the American Heart Association journal Circulation, gives an overview of what is currently understood regarding sleep problems and cardiovascular-related risk factors. It also asks if improving sleep would decrease these risk factors and, therefore, the risk of heart disease.
Risk factors that are associated with both sleep irregularities and heart disease include obesity, type 2 diabetes, heart disease and atherosclerosis, arrhythmias, high blood pressure, stroke, and unhealthy levels of triglycerides and cholesterol.
An estimated 50-70 million people in the United States have ongoing sleep disorders, and 29.1 American adults report less than 7 hours of sleep.
The American Academy of Sleep Medicine and Sleep Research Society recommend that adults should get at least 7 hours of sleep per night to promote overall health. However, the American Heart Association does not have a recommendation on how much sleep is needed for cardiovascular wellness, as there is currently not enough scientific evidence to base a recommendation.
Excessive or insufficient sleep linked to heart disease
"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," says Marie-Pierre St-Onge, Ph.D., associate professor of nutritional medicine at Columbia University in New York City, and chair of the panel that reviewed the science behind sleep disorders and heart disease.
"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," she adds.
According to the National Sleep Foundation, sleep is essential for a healthy heart. Individuals who do not sleep between 6-8 hours per night are at a greater risk for cardiovascular disease regardless of age, weight, smoking, and exercise habits. Lack of sleep is linked to stress, increased blood pressure, and adrenaline secretion - all heart disease risk factors.
While the reasons behind why not getting enough sleep is detrimental to heart health are unclear, scientists indicate that less sleep causes disruptions to underlying health conditions and biological processes such as glucose metabolism, blood pressure, and inflammation.
However, sleeping too much - beyond 8 hours - may carry the same risks of dying from coronary artery disease as having too little sleep, which suggests that there is a fine balance between sleep duration and heart health.
Obesity, diabetes risk increases with altered sleep
Most research on sleep disorders and heart disease centers on sleep apnea and insomnia.
The prevalence of sleep apnea - a potentially serious sleep disorder where breathing stops and starts repeatedly - is high in people with cardiovascular problems including hypertension, heart failure, and stroke.
When individuals with heart failure and sleep apnea, or high blood pressure and sleep apnea are treated, the measures of high blood pressure or heart failure significantly improve.
Underlying heart conditions including angina or heart failure can cause insomnia - defined as difficulty falling or staying asleep. Heart and blood pressure medications can also interfere with sleep.
St-Onge notes that of the cardiovascular-related risk factors, evidence linking sleep problems to obesity and diabetes have been studied the most. "Those are the two main conditions in which there are intervention studies that show that risk factors are increased when sleep is altered," she explains.
Studies have shown that sleep influences food intake, and, as a result, directly impacts on the risk of obesity, she continues. However, the research has only been for short periods, and St-Onge says that longer studies that measure the impact specifically on weight are required.
Being overweight or obese can raise blood cholesterol levels, increase blood pressure and increase the risk of type 2 diabetes - risk factors for coronary heart disease.
Longer studies may help identify if sleep variations over the course of weeks affect patients' blood cholesterol, triglycerides, or inflammatory markers.
Sleep just as important as physical activity, diet
Previous research linking poor sleep to diabetes, hypertension, and cardiovascular disease has been mostly observational, which establishes a connection, without proving that sleep problems cause these conditions. More research is needed to provide better causal evidence, says St-Onge.
Additionally, St-Onge states that healthcare providers should ask patients about how long they sleep, how well they sleep, and if they snore, to help determine if they are at an increased risk of heart disease.
"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. Sleep is another type of ammunition that we can tailor to improve health."
Marie-Pierre St-Onge, Ph.D.
People can be assisted with decreasing heart disease-related risk factors with intervention. Individuals who are overweight, or who are obese and snore, should be referred to a sleep specialist to analyze for sleep apnea. Likewise, people who experience inadequate sleep or insomnia should receive follow-up evaluations, St-Onge concludes.