Associations Between Sleep Duration and Prevalence of Cardiovascular Events
What is the association between self-reported sleep duration and cardiovascular (CV) events?
This was a questionnaire-based study including subjects who answered questions on sleep duration and CV events among a general population recruited between 2007 and 2008, in the National Health and Nutrition Examination Survey. Sleep duration was extracted from a questionnaire and classified: <6 hours, 6-8 hours, or >8 hours. Data regarding CV endpoints of congestive heart failure (CHF), myocardial infarction (MI), stroke, coronary artery disease (CAD), and angina were extracted from yes/no questionnaires. Associations were adjusted for sex, age, body mass index, total cholesterol level, high-density lipoprotein cholesterol, smoking status, systolic blood pressure, history of sleep apnea, and family history of heart attack.
A total of 10,149 subjects were surveyed and 6,538 reported on sleep duration. Average sleep duration was 6.85 ± 1.49 hours. Significant differences in age at screening, smoking status, and ethnicity were noted between those in various sleep-duration classifications. Those sleeping <6 hours were more likely to be young, smoke, and of nonethnic background. Not all reported CV events. The following numbers of patients were finally available for each reported event: 3,011 for CHF, 3,019 for MI, 3,015 for stroke, 3,012 for angina, and 3,014 for CAD. There was a statistically significant increase in stroke in those with <6 hours of sleep (odds ratio [OR], 2.01; 95% confidence interval [CI], 1.43-2.81), in MI in those with <6 hours of sleep (OR, 2.04; 95% CI, 1.48-2.82), in CHF in those with <6 hours of sleep (OR, 1.67; 95% CI, 1.15-2.41), in CAD in those with >8 hours of sleep (OR, 1.19, 95% CI, 1.07-3.42), and in angina in those with >8 hours of sleep (OR, 2.07; 95% CI, 1.04-4.08).
The authors concluded that shorter sleep duration is associated with greater prevalence of stroke, MI, and CHF. Longer sleep duration was associated with higher prevalence of CAD and angina.
The mechanisms explaining the associations of sleep patterns and prevalence of CV diseases are not well understood. Shorter sleep duration has a variety of effects, including activation of the sympathetic nervous system, glucose intolerance, increased cortisol levels, and increased blood pressure. Strengths of the study are that the database is representative of the US population, it reported on five different CV endpoints, and results were adjusted for all traditional CV risk factors including sleep apnea. However, it is noted that sleep apnea remains largely undiagnosed in the majority of the population, so this adjustment may not have been complete. Bias may have also been created by subjects equating sleep time as time lying awake in bed. Long duration of follow-up in large populations will be needed to achieve any significant outcomes in prospective studies.
Keywords: Deception, Odds Ratio, Coronary Artery Disease, Myocardial Infarction, Stroke, Follow-Up Studies, Sleep, Risk Factors, Blood Pressure, Smoking, Sleep Apnea Syndromes, Prevalence, Glucose Intolerance, Cholesterol, Body Mass Index, Sympathetic Nervous System, Heart Failure, Cardiovascular Diseases, Confidence Intervals, Questionnaires, Lipoproteins, HDL, Hydrocortisone
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