Association between habitual naps and sleep apnea

STUDY OBJECTIVES: Taking an afternoon nap (siesta) is a common habit. A number of studies have shown an increased cardiovascular mortality in habitual nappers. Afternoon nappers have anthropometric characteristics similar to those of patients with sleep apnea. Nappers appear to suffer from more sleep apnea, which could contribute to cardiovascular disorders. Our aim was therefore to determine the association between sleep apnea and napping, as well as to analyze the relationship of sleep apnea and napping with hypertension. DESIGN: Case-control study. SETTING: Residents in the town of Caceres (Spain) with a population of 100,000 inhabitants. PARTICIPANTS: Four hundred five individuals were initially selected (186 nappers and 219 nonnappers). INTERVENTIONS: Telephone interviews were conducted to contact habitual nappers and nonnappers. Out of the total population selected, 90 nappers and 88 nonnappers completed the study protocol (personal interview and polysomnography). MEASUREMENTS AND RESULTS: The nappers had a higher frequency of sleep apnea at the 3 cutoff points studied (apnea and hypopnea index > or = 5, > or = 10, > or = 15). The adjusted odds ratio was between 2.8 (confidence interval, 1.3-5.8) and 5.5 (confidence interval, 2.3-13). Napping was associated with hypertension in the univariate analysis (odds ratio: 2.1; confidence interval, 1.1-4), but this association disappeared once sleep apnea was included as a covariate in the multivariate modeling (odds ratio dropped to 1.1). CONCLUSIONS: Our findings suggest that napping could be regarded as a marker of sleep apnea, which could account for the cardiovascular diseases observed in nappers. Given that napping is common and that sleep apnea is treatable, more attention should be focused on this population.