Midday Naps and the Risk of Coronary Artery Disease: Results of the Heinz Nixdorf Recall Study
Do midday naps increase risk for cardiovascular disease?
Data from the Heinz Nixdorf Recall Study were used for the present analysis. Between December 2000 and August 2003, participants (ages 45-75 years) residing in the industrial cities Essen, Bochum, and Mülheim, all in Germany, were enrolled. Annual postal questionnaires assessed the morbidity status including hospital admissions, and outpatient diagnoses of cardiovascular disease. Self-reported incident cardiovascular morbidity was validated by review of medical records, and death records were regularly reviewed. Additional measures included physical examinations, laboratory tests, and electron beam computed tomography. The primary outcome of interest was cardiac events (nonfatal myocardial infarction and sudden cardiac death) occurring during a median follow-up of 8.1 years.
A total of 4,123 participants were included in the present analysis, of which 16.3% (n = 671) reported taking regular naps. Frequency of naps was associated with nap duration among women, but not among men. Self-reported sleep durations of regular nap takers showed peaks at 30 minutes, 60 minutes, and 90 minutes. Napping was not associated with the self-reported median sleep duration at night. Regular long nap takers more frequently reported a poor self-perceived health status and more frequently were depressive, according to the Center for Epidemiologic Studies Depression (CES-D) scale. Regular nap takers were older among both men and women. During the 8.1 years of follow-up, 135 (3.3%) participants experienced an acute myocardial infarction (81 subjects) or died due to a sudden cardiac death (54 subjects). After adjustment for several confounders including measures of subclinical atherosclerosis, regular long (>60 minutes) midday naps were associated with an increased hazard ratio (HR) of cardiac events (HR, 2.12; 95% confidence interval, 1.11-4.05).
The investigators concluded that midday naps >60 minutes are associated with increased risk for cardiac events.
This is a very interesting finding, suggesting that longer duration naps are a marker of poor health. This study was well done in that adjustment of multiple traditional risk factors, in addition to markers of subclinical atherosclerosis, was completed. Unfortunately, adjustment of sleep apnea was not able to be performed. Further examination, in particular sleep characteristics in association with daytime napping, is warranted.
Keywords: Coronary Artery Disease, Myocardial Infarction, Follow-Up Studies, Atherosclerosis, Tomography, Cardiology, Cardiovascular Diseases, Sleep, Calcinosis, Risk Factors, Germany, Sleep Apnea Syndromes
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