Daytime Napping and the Risk of Cardiovascular Disease and All-Cause Mortality: A Prospective Study and Dose-Response Meta-Analysis - PubMed (original) (raw)

Meta-Analysis

Daytime Napping and the Risk of Cardiovascular Disease and All-Cause Mortality: A Prospective Study and Dose-Response Meta-Analysis

Tomohide Yamada et al. Sleep. 2015.

Abstract

Study objectives: To summarize evidence about the association between daytime napping and the risk of cardiovascular disease and all-cause mortality, and to quantify the potential dose-response relation.

Design: Meta-analysis of prospective cohort studies.

Methods and results: Electronic databases were searched for articles published up to December 2014 using the terms nap, cardiovascular disease, and all-cause mortality. We selected well-adjusted prospective cohort studies reporting risk estimates for cardiovascular disease and all-cause mortality related to napping. Eleven prospective cohort studies were identified with 151,588 participants (1,625,012 person-years) and a mean follow-up period of 11 years (60% women, 5,276 cardiovascular events, and 18,966 all-cause deaths). Pooled analysis showed that a long daytime nap (≥ 60 min/day) was associated with a higher risk of cardiovascular disease (rate ratio [RR]: 1.82 [1.22-2.71], P = 0.003, I(2) = 37%) compared with not napping. All-cause mortality was associated with napping for ≥ 60 min/day (RR: 1.27 [1.11-1.45], P < 0.001, I(2) = 0%) compared with not napping. In contrast, napping for < 60 min/day was not associated with cardiovascular disease (P = 0.98) or all-cause mortality (P = 0.08). Meta-analysis demonstrated a significant J-curve dose-response relation between nap time and cardiovascular disease (P for nonlinearity = 0.01). The RR initially decreased from 0 to 30 min/day. Then it increased slightly until about 45 min/day, followed by a sharp increase at longer nap times. There was also a positive linear relation between nap time and all-cause mortality (P for non-linearity = 0.97).

Conclusions: Nap time and cardiovascular disease may be associated via a J-curve relation. Further studies are needed to confirm the efficacy of a short nap.

Keywords: all-cause mortality; cardiovascular disease; meta-analysis; napping; siesta.

© 2015 Associated Professional Sleep Societies, LLC.

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Figures

Figure 1

Figure 1

Literature search and study selection.

Figure 2

Figure 2

Meta-analysis of the incidence rate ratio of cardiovascular disease. Plots showing the association between daytime napping and the risk of cardiovascular disease. *Number of available datasets. In seven reports, the results were stratified by sex (male/female), while results were stratified by age group in 1 report (50 to 64 years, 65 to 74 years, and ≥ 75 years), by nocturnal sleep duration in 1 report (< 7 h, 7 to 7.9 h, 8 to 8.9 h, 9 to 9.9 h, and ≥ 10 h), and by the presence of hypertension in 1 report (hypertension group, non-hypertension group). CI, confidence interval.

Figure 3

Figure 3

Meta-analysis of the incidence rate ratio of all-cause mortality. Plots showing the association between daytime napping and the risk of all-cause mortality. *Number of available datasets. CI, confidence interval.

Figure 4

Figure 4

Dose-response relationship between nap time and the risk of cardiovascular diseases. CI, confidence interval.

Figure 5

Figure 5

Dose-response relationship between nap time and the risk of all-cause mortality. CI, confidence interval.

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