Geographical Variations of the Minimum Mortality Temperature at a Global Scale: A Multicountry Study

BACKGROUND: Minimum mortality temperature (MMT) is an important indicator to assess the temperature-mortality association, indicating long-term adaptation to local climate. Limited evidence about the geographical variability of the MMT is available at a global scale. METHODS: We collected data from 658 communities in 43 countries under different climates. We estimated temperature-mortality associations to derive the MMT for each community using Poisson regression with distributed lag non-linear models. We investigated the variation in MMT by climatic zone using a mixed-effects meta-analysis and explored the association with climatic and socio-economic indicators. RESULTS: The geographical distribution of MMTs varies considerably by country between 14.2°C to 31.1°C decreasing by latitude. For climatic zones, the MMTs increases from alpine (13.0°C) to continental (19.3°C), temperate (21.7°C), arid (24.5°C) and tropical (26.5°C). The MMT percentiles (MMTPs) corresponding to the MMTs decrease from temperate (79.5th) to continental (75.4th), arid (68.0th), tropical (58.5th) and alpine (41.4th). The MMTs increases by 0.8°C for a 1°C rise in a community’s annual mean temperature, and by 1°C for a 1°C rise in its standard deviation. While, the MMTP decreases by 0.3 centile points for a 1°C rise in a community’s annual mean temperature and by 1.3 for a 1°C rise in its standard deviation. CONCLUSIONS: The geographical distribution of the MMTs and MMTPs is driven mainly by the mean annual temperature, which seems to be a valuable indicator of overall adaptation across populations. Our results suggest that populations have adapted to the average temperature, although there is still more room for adaptation.