Association of ambient temperature with mortality in resident and multiethnic transient populations in a desert climate, 2006–2014

We aimed to characterize the ambient temperature-mortality relationship and burden for the Mecca resident and Hajj transient populations, which have distinct levels of adaptation to ambient temperature. Although the association between ambient temperature and mortality in local populations is evident, this relationship remains unclear in transient populations (e.g., due to immigration, mass gatherings, or displacement). The holy city of Mecca annually shelters two populations comprising its residents and the transitory Hajj pilgrims (>2 million people from >180 countries).

The results indicate a nonlinear exposure response, with a significant association of heat with risk of mortality among pilgrims. The findings will help direct more targeted public health interventions to reduce the burden of illness and death related to nonoptimal temperatures for pilgrims and Mecca residents. In particular, stricter implementation of heat-illness prevention strategies, including focused health education and improving the adherence of pilgrims to preventive measures.