Temperature and mortality on the roof of the world: a time-series analysis in three Tibetan counties, China.

BACKGROUND: Tibet, with an average altitude of more than 4,000 meters, is warming faster than anywhere else in China. However, there have been no studies in Tibet of the relation between ambient temperature and mortality. METHODS: We examined mean temperature and daily mortality in three Tibetan counties (Chengguan, Jiangzi and Naidong) using a distributed lag non-linear model (DLNM) based on 5,610 deaths that occurred in 2008-2012. We separately investigated hot and cold effects on non-accidental deaths, cardiovascular deaths, out-of-hospital deaths and vulnerability factors including age, sex and education. RESULTS: In all three counties, the effect of heat tended to be immediate, while the impact of cold lasted longer. The effects were consistent but modest in size and not statistically significant except for cumulative cold effects in Jiangzi (lag=0-14, RR=2.251, 95% CI=1.054-4.849). Those who were more vulnerable to temperature extremes tended to be men, the elderly (over 65 years) and illiterate persons. We found stronger temperature effects on cardiovascular deaths than on all-cause mortality, and we also observed an increase in out-of-hospital mortality in one county. CONCLUSIONS: This is the first study to investigate the temperature-mortality relationship in Tibet, and the findings may guide public health programs and other interventions to protect the population against extreme temperatures in a developing Tibet.