Respiratory morbidity and extreme temperatures in the 21st century: a projection analysis in a semi-arid region of Iran

This study aimed to project heat- and cold-related respiratory morbidity throughout the 21st century. The baseline impact of heat and cold was estimated using a semi-parametric model, including an exposure metric derived from remote-sensing and monitoring station data. Attributable fractions (AFs) of respiratory morbidity were estimated from 2020 to 2100, accounting for adaptation (30%) and population fertility scenarios (low and high). We also projected the effect estimates by adjusting for greenness (NDVI) in the modeling process. Cold-related AFs were higher than heat-related AFs under all scenarios, however the cold effect declined, while the heat effect increased throughout the century, particularly under RCP8.5. The cold-related AF was statistically significant in 2020–2029 (AFRCP2.6: 46.8%; 95% CI: 0.91, 60.29, AFRCP4.5: 47.01%; 95% CI: 2.56, 59.4, AFRCP8.5: 46.62%; 95% CI: 0.93, 59.97), while there was big uncertainty in other decades and for heat-related estimates. Accounting for adaptation substantially reduced both heat and cold-related AFs, with a higher reduction for cold. Adjustment for greenness slightly reduced the uncertainty of cold-related estimates. Overall, climate change is likely to shift the burden of respiratory morbidity from cold -related to heat-related extremes in future. Adaptation measures and urban greening strategies should be considered when developing climate-related health adaptation plans.