Daytime Napping and the Risk of All-Cause and Cause-Specific Mortality: A 13-Year Follow-up of a British Population

Y Leng,S Hayat,C Brayne,N W J Wainwright,R Luben,K.-T Khaw,P G Surtees,F P Cappuccio

doi:10.1093/aje/kwu036

Abstract

Epidemiologic studies have reported conflicting results on the relationship between daytime napping and mortality risk, and there are few data on the potential association in the British population. We investigated the associations between daytime napping and all-cause or cause-specific mortality in the European Prospective Investigation Into Cancer-Norfolk study, a British population-based cohort study. Among the 16,374 men and women who answered questions on napping habits between 1998 and 2000, a total of 3,251 died during the 13-year follow-up. Daytime napping was associated with an increased risk of all-cause mortality (for napping less than 1 hour per day on average, hazard ratio = 1.14, 95% confidence interval: 1.02, 1.27; for napping 1 hour or longer per day on average, hazard ratio = 1.32, 95% confidence interval: 1.04, 1.68), independent of age, sex, social class, educational level, marital status, employment status, body mass index, physical activity level, smoking status, alcohol intake, depression, self-reported general health, use of hypnotic drugs or other medications, time spent in bed at night, and presence of preexisting health conditions. This association was more pronounced for death from respiratory diseases (for napping less than 1 hour, hazard ratio = 1.40, 95% confidence interval: 0.95, 2.05; for napping 1 hour or more, hazard ratio = 2.56, 95% confidence interval: 1.34, 4.86) and in individuals 65 years of age or younger. Excessive daytime napping might be a useful marker of underlying health risk, particularly of respiratory problems, especially among those 65 years of age or younger. Further research is required to clarify the nature of the observed association.

Highlights

Other covariates were reported in questionnaires during the time of the second health check: age, marital status, employment status, smoking status, alcohol intake, self-reported general health, use of hypnotic drugs, antidepressant use, use of drugs to treat chronic obstructive pulmonary disease (COPD), major depressive disorder (MDD) in the previous year [23], and time spent in bed at night
Models were constructed with progressive adjustment of the covariates to show the associations explained by the covariates: 1) Model A was adjusted for age and sex; 2) model B was further adjusted for social class, educational level, marital status, employment status, Body mass index (BMI), physical activity level, smoking status, and alcohol intake; 3) model C was adjusted for the variables in model B and MDD, self-reported general health, time spent in bed at night, hypnotic drug use, antidepressant use, and COPD drug use; and 4) model D was further adjusted for the variables in all models and preexisting health conditions
The hazard ratios were attenuated to 1.14 for napping less than 1 hour and 1.34 for napping 1 hour or longer after further adjustment for social class, educational level, marital status, employment status, BMI, physical activity level, smoking status, alcohol intake, MDD, self-reported general health, hypnotic drug use, antidepressant and COPD drug use, and time spent in bed at night

Summary

Introduction

There has been growing evidence of a relationship between habitual sleep and the risk of mortality from all-causes and cardiovascular diseases (CVDs) [1,2,3] Most of these studies focused on nighttime sleep duration [4, 5]; the implications of daytime napping are poorly understood. 2014;179(9):1115–1124 research has found an increased risk of death associated with daytime napping in both men only [14] and women only [15] In both studies, only naps of long durations were found to be significant. Epidemiologic evidence ofthe association between daytime napping and mortality is inconsistent and dependent on cultural, environmental, and demographic factors [19] It remains unclear whether napping is beneficial or a risk factor for or marker of ill health.

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Conclusion