A systematic review of ambient heat and sleep in a warming climate

Abstract

AbstractBackgroundEarlier reviews documented the effects of a broad range of climate change outcomes on sleep but have not yet evaluated the effect of ambient temperature. This systematic review aims to identify and summarize the literature on ambient temperature and sleep outcomes in a warming world.MethodsFor this systematic review, we searched online databases (PubMed, Scopus, JSTOR, GreenFILE, GeoRef and PsycARTICLES) together with relevant journals for studies published before February 2023. We included articles reporting associations between objective indicators of ambient temperature and valid sleep outcomes measured in real-life environments. We included studies conducted among adults, adolescents, and children. A narrative synthesis of the literature was then performed.FindingsThe present systematic review shows that higher outdoor or indoor ambient temperatures, expressed either as daily mean or night-time temperature, are negatively associated with sleep quality and quantity worldwide. The negative effect of higher ambient temperatures on sleep is stronger in the warmest months of the year, among vulnerable populations and in the warmest areas of the world. This result appears consistent across several sleep indicators and measures.InterpretationAlthough this work identified several methodological limitations of the extant literature, a strong body of evidence from both this systematic review and previous experimental studies converge on the negative impact of elevated temperatures on sleep quality and quantity. In absence of solid evidence on fast adaptation to the effects of heat on sleep, rising temperatures induced by climate change pose a planetary threat to human sleep and therefore human health, performance and wellbeing.