CHICAGO – Sleeping too much as well as too little appears to be detrimental to cardiovascular health, according to large retrospective analysis of the NHANES database.
Individuals who slept less than 6 hours per day had twice the risk of myocardial infarction (odds ratio 2.04) or stroke (OR 2.01), compared with those who slept 6-8 hours, even after adjusting for a multiple confounders associated with cardiovascular risk.
Individuals with less than 6 hours of sleep duration were also at increased risk of heart failure (OR 1.67), Dr. Rohit R. Arora reported at the annual meeting of the American College of Cardiology.
Intriguingly, persons who slept more than 8 hours per night had a twofold increased risk of angina (OR 2.07) as well as an increased risk of coronary artery disease (OR 1.19).
"It seems that the optimal time is 6 to 8 hours," said Dr. Arora, chair of cardiology and professor of medicine at the Chicago Medical School.
He stressed that the analysis could not establish a cause-and-effect relationship, but suggested that patients who sleep more than 8 hours per night may do so because of underlying comorbid conditions such as chronic obstructive pulmonary disease and diabetes or low socioeconomic status, all of which could contribute to their cardiovascular risk.
Previous studies have shown that insufficient sleep is associated with hyperactivation of the sympathetic nervous system, glucose intolerance, an increase in cortisol levels and blood pressure, decreased variability in heart rate, disruption of the hypothalamic axis, and a general increase in inflammatory markers.
The analysis included 3,019 individuals, at least 45 years of age, who participated in the 2007-2008 National Health and Nutrition Examination Survey (NHANES). Patients were asked about sleep quality and then stratified into one of three categories: fewer than 6 hours of sleep a night, 6-8 hours a night, and more than 8 hours of sleep per night.
The analysis adjusted for the covariates of age, systolic blood pressure, gender, body mass index, diabetes, smoking status, total cholesterol, HDL-cholesterol, sleep apnea, and family history of heart attack. The analysis could not determine the underlying level of cardiovascular or cerebrovascular disease in the participants, nor did it evaluate quality of sleep, which emerging data suggests plays a role in certain cardiovascular outcomes, Dr. Arora said.
What is clear from the analysis is that providers should talk to their patients about their sleep, particularly those who are at greater risk for heart disease. The data also support a recommendation for 6-8 hours of sleep per night in current guidelines. As for whether this recommendation should be given early on in life to adolescents, who are known to have inadequate sleep, the recommendation would not be amiss, he said in an interview.
Dr. Arora reported no relevant conflicts of interest.