Daytime napping and coronary heart disease risk in adults: a systematic review and dose-response meta-analysis

The present study investigated the association between daytime napping and coronary heart disease (CHD) risk among adults.

Articles were detected by using PubMed, ISI Web of Science, and Scopus databases until November 8th, 2021. The relevant data were found among the eight included articles and were pooled for meta-analysis in adult participants via a random-effects model.

Among 167,025 adults, the results revealed that daytime napping was associated with an enhanced risk of CHD (risk ratios [RR] = 1.30; 95% CI: 1.06, 1.60; p < 0.001). Subgroup analysis by daytime napping duration also indicated that daytime napping for at least 1 h had three times higher influence on the enhanced risk of CHD (RR = 1.34; 95% CI: 1.14, 1.58; p < 0.001) than that of daytime napping for less than 1 h (RR = 1.10; 95% CI: 1.02, 1.19; p = 0.014). In addition, subgroup analysis by region illustrated that daytime napping was linked with an enhanced risk of CHD in Chinese (RR = 1.41; 95% CI: 1.19, 1.66; p < 0.001), but not in European or American populations. Furthermore, the subgroup analysis of napping duration and risk of CHD suggested that their relation was significant just in those studies that controlled for depressive symptoms (RR = 1.52; 95% CI: 1.29, 1.80; p < 0.001, n = 3) and night sleep duration (RR = 1.42; 95% CI: 1.21, 1.66; p < 0.001, n = 5). The linear dose-response meta-analysis revealed that each 15-min increase in daytime napping was related with a 5% higher risk of CHD (RR = 1.05; 95% CI: 1.02, 1.08; I² = 58.7%; p < 0.001). Furthermore, nonlinear dose-response meta-analysis revealed a positive linear relationship between daytime napping and CHD risk in adults (p nonlinearity = 0.484, p dose-response = 0.003).

Results showed that daytime napping was related with an increased risk of CHD in adults. The evidence from this study suggests that the public should be made conscious of the adverse outcomes of long daytime napping for CHD, notably among the Chinese population. Additional studies are required to confirm potential links between CHD risk and daytime napping.