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This study was designed to investigate the relationship between daytime napping duration and cardiovascular mortality based on a 10 years’ observation.
5042 patients (2349 males and 2693 females, 63.9±11.1 years) with a follow-up period of 10 years, between January 1994 and November 2011 were recruited and studied. We defined daytime nap on the basis of affirmative answers to questions such as “Do you take a daytime nap?” or “Do you sleep during the day?” Descriptive statistics are presented as percentages for discrete variables and as means (standard deviation) for continuous variables. Cox regression analysis was used to estimate the hazard ratio (HR) and 95% confidence intervals (95% CI) for relationship between daytime napping and cardiovascular mortality.
Among the 5024 men and women who answered questions on napping habits between 1994 and 2011, a total of 359 cardiovascular death (197 males and 162 females) was observed during the 10-year follow-up. Daytime nappers tends to have higher cardiovascular mortality than patients not taking naps (40.5% vs. 29.2%, P=0.001). In addition, the results of cox regression analysis showed that daytime napping duration ≥30min/day (HR 1.489, 95% CI 1.070-2.073, P=0.018) were significantly associated with cardiovascular mortality.
Our results indicated that prolonged daytime nap might be a risk for cardiovascular mortality. However, further research is required to clarify the mechanism.