To nap or not to nap: evidence on daytime napping and increased 13-year mortality in a British population

Abstract

The prevalence of napping increases with age. Epidemiological studies have reported conflicting results on the relation between daytime napping and mortality. Most studies have been conducted in the Mediterranean area, while the association is underreported among the British population. In this analysis, we aimed to explore the independent associations between daytime napping and cause-specific mortality among participants in EPIC-Norfolk, a British population based study. Between 1998 and 2000, 16374 participants (7161 men and 9213 women) aged 40–82 years, answered questions on napping habits (No/Yes, <1 h/Yes, >= h) as well as other factors. They were followed for mortality until Dec 2012. At baseline, the prevalence of day time napping was 29.8%, of whom 90% reported napping for less than 1 h/day. A total of 3251 deaths (1034 from CVD, 1213 from cancer, 286 from respiratory diseases and 718 from all other causes) was observed. The unadjusted HRs (95% CI) of napping for all-cause mortality were 2.19 (2.04–2.36) (napping < 1 h) and 2.67 (2.28–3.13) (>= h). After adjustment for age, sex, social class, education and marital status, there was a dose–response association between napping and increased mortality from all causes (HR 1.23 [95% C.I. 1.14–1.33] for napping <1 h and 1.59 [1.35–1.87] for >= h), CVD, cancer, respiratory diseases and all other causes. The associations between napping and CVD or cancer mortality were attenuated after further adjustment for body mass index, physical activity, smoking, alcohol, hypnotic use, depression, time spent in bed at night, self-reported general health and obstructive sleep apnea (OSA). However, a strong association remained between napping and all-cause mortality (HR 1.28 [1.03–1.61] for >= h) and between napping and respiratory mortality (HR 2.33 [1.21–4.10] for >= h) after full adjustment. The association between napping and all-cause mortality remained after exclusion of individuals with pre-existing CVD, cancer, respiratory diseases and OSA, and did not attenuate with increasing length of follow up. Daytime napping is independently associated with increased all- cause mortality and respiratory mortality in a middle aged and older British population. Future studies are needed to confirm our finding and help understand potential mechanisms. EPIC-Norfolk study was supported by programme grants from the Medical Research Council UK (G9502233, G0300128) and Cancer Research UK (C865/A2883).