Sleep health epidemiology in low and middle-income countries: a systematic review and meta-analysis of the prevalence of poor sleep quality and sleep duration.

Sleep research has been dominated by high income countries (HIC). Sleep may be different in low and middle income countries (LMIC) due to cultural, demographic, geographical and health factors. We systematically reviewed the epidemiological literature reporting sleep parameters in the adult population in LMIC and meta-analyzed the prevalence of subjective poor sleep quality and sleep duration. We identified 45 publications; over 50% of which came from China and Brazil. Of the 45 identified studies, 32 contained data on sleep quality and 17 on self-reported sleep duration. Only one study utilized polysomnography and only one study utilized actigraphy. This review provides evidence that sleep parameters in LMIC appear to be similar to those in HIC but the variability and bias found suggests any attempt to extract a universal prevalence estimate or average sleep duration from the current data is very likely flawed and should be taken with caution. In our meta-analysis we found an enormous variability that was not explicable by regional, rurality, gender, age group or sleep assessment method. Further, there was a suggestion of significant small study effect, with smaller studies reporting worse sleep. There is surprisingly little consistent high-quality data that could be used for policy, planning, or scientific purposes at a global level in low and middle-income countries about what humans spend a third of their lives doing. High-quality epidemiological research about basic sleep health parameters is needed that focuses on the whole-population in LMIC, and that uses standardized, well-validated and culturally applicable measures.