Objective There is controversy regarding the effect of napping on cardiovascular disease (CVD), with most studies failing to consider napping frequency. We aimed to assess the relationship of napping frequency and average nap duration with fatal and non-fatal CVD events.
Methods 3462 subjects of a Swiss population based cohort with no previous history of CVD reported their nap frequency and daily nap duration over a week, and were followed over 5.3 years. Fatal and non-fatal CVD events were adjudicated. Cox regressions were performed to obtain HRs adjusted for major cardiovascular risk factors and excessive daytime sleepiness or obstructive sleep apnoea.
Results 155 fatal and non-fatal events occurred. We observed a significantly lower risk for subjects napping 1–2 times weekly for developing a CVD event (HR 0.52, 95% CI 0.28 to 0.95) compared with non-napping subjects, in unadjusted as well as adjusted models. The increased HR (1.67, 95% CI 1.10 to 2.55) for subjects napping 6–7 times weekly disappeared in adjusted models (HR 0.89, 95% CI 0.58 to 1.38). Neither obstructive sleep apnoea nor excessive daytime sleepiness modified this lower risk. No association was found between nap duration and CVD events.
Conclusion Subjects who nap once or twice per week have a lower risk of incident CVD events, while no association was found for more frequent napping or napping duration. Nap frequency may help explain the discrepant findings regarding the association between napping and CVD events.
- frequency of napping
- cardiovascular disease
- population-based cohort
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JH-R, RH and PM-V contributed equally.
Contributors NH performed the statistical analyses and wrote the article. PM-V collected the data and revised the article for important intellectual content. RH and JH-R devised the study and revised the article for important intellectual content. PM-V has full access to the data and is the guarantor of the study.
Funding The CoLaus study was and is supported by research grants from GlaxoSmithKline, the Faculty of Biology and Medicine of Lausanne and the Swiss National Science Foundation (grant Nos 33CSCO- 122661, 33CS30-139468 and 33CS30-148401). PM-V received a grant from the Swiss National Science Foundation (320030E_176280) to analyse the associations between sleep and cardiovascular disease.
Competing interests PM-V received a grant from the Swiss National Science Foundation (320030E_176280) to analyse the associations between sleep and cardiovascular disease.
Ethics approval The institutional ethics committee of the University of Lausanne, which afterwards became the Ethics Commission of Canton Vaud (www.cer-vd.ch) approved the CoLaus study (reference 16/03, decisions on 13 January and 10 February 2003) and the approval was renewed for the follow-ups (reference 33/09, decision 23 February 2009; reference 26/14, decision 11 March 2014). The study complies with the Declaration of Helsinki and written informed consent was obtained from all participants.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Due to the sensitivity of the data and the lack of consent for online posting, individual data cannot be made accessible. Only metadata will be made available in digital repositories. Metadata requests can also be performed via the study website www.colaus-psycolaus.ch.
Patient consent for publication Not required.