Effect of diurnal fasting on sleep during Ramadan: a systematic review and meta-analysis

Purpose The current meta-analysis aimed to obtain a more stable estimate of the effect size of Ramadan diurnal intermittent fasting (RDF) on sleep duration and daytime sleepiness. Methods Databases (Scopus, ScienceDirect, ProQuest Medical, PubMed/MEDLINE, Web of Science, EBSCOhost, Cochrane, CINAHL, and Google Scholar) were searched from database inception to the end of June 2019. The sleep quality measures analyzed were excessive daytime sleepiness (EDS) measured by the Epworth sleepiness scale (ESS) and total sleep time (TST). Subgroup analyses for age, sex, and levels of physical activity were conducted. Results We identified 24 studies (involving 646 participants, median age 23.7 years, 73% men) conducted in 12 countries from 2001 to 2019. The results revealed that TST decreased from 7.2 h per night [95% confidence interval (CI) 6.7–7.8] before Ramadan to 6.4 h (95% CI 5.3–7.5) during Ramadan, while the ESS score increased slightly from 6.1 (95% CI 4.5–7.7) before Ramadan to 7.0 (95% CI 5.2–8.8) during Ramadan. Effect sizes on sleep quality measures during RDF demonstrated a moderate reduction in TST (number of studies, K = 22; number of subjects, N = 571, Hedges’ g value of −0.43, 95% CI − 0.64 to −0.22, Q = 90, τ 2 = 0.15, I 2 = 78%, P < 0.001), while ESS score showed negligible effect on EDS (K = 9, N = 362, Hedges’ g value of −0.06, 95% CI −0.43 to 0.28, Q = 21, τ 2 = 0.13, I 2 = 76%, P value = 0.001). Conclusion During the month of Ramadan, there is approximately a 1 hour reduction in TST and nearly a 1 point increase in the ESS score.