Minimum mortality temperature by cause of death and age group: A multi-country observational study (1990-2019)

Minimum mortality temperature (MMT) is an important feature of temperature-mortality relationship, defined as the temperature at which mortality risk is lowest. Although numerous studies have estimated MMT for all-cause mortality, few have explored differences by age or cause of death. We analyzed daily mean temperature and mortality data from 667 communities across 39 countries. Mortality was classified by age and cause of death (cardiovascular, respiratory, or non-cardiorespiratory). A two-stage meta-analytic approach was applied to estimate the MMT and its corresponding percentile (MMTP) by age and cause of death. In the overall population, MMT was the highest for cardiovascular mortality (22.1 °C, 95% CI: 20.9-23.4 °C), whereas respiratory and non-cardiorespiratory causes were 0.87 °C and 0.66 °C lower, respectively, than that for cardiovascular causes. Similar patterns were observed for MMTP, which was highest for cardiovascular mortality (75%, 95% CI: 73-78%) and lower by 5% and 4% for respiratory and non-cardiorespiratory causes, respectively. MMT increased with age for cardiovascular (0.19 °C per 10 years, 95% CI: 0.14-0.23) and non-cardiorespiratory causes (0.13 °C per 10 years, 95% CI: 0.09-0.16). These patterns were generally consistent across geographical regions. Overall, both MMT and MMTP differed by cause of death and age, indicating that the optimal temperature varies across population subgroups.