Compound drought and heatwave events and childhood diarrhea: current impacts and future risk in low- and middle-income countries

The risk of childhood diarrhea related to compound drought and heatwave (CDHW) remain unclear at present and in the future under climate change scenarios. We used information on diarrhea prevalence from the Demographic and Health Surveys. Three indicators considering heatwave frequency (HWF), intensity (HWEMD), and cumulative heat (CH) were used. CDHW was defined as drought and heatwave occurred simultaneously. A modified Poisson regression model was employed to estimate the association between CDHW and diarrhea. Then the association was used to project the excess risk of CDHW-related childhood diarrhea by climate zones and regions under different climate scenarios. A total of 64,429 children under five years were included. The relative risk (RR) of CDHWs (e.g., compound severe HWF and severe drought; RR = 1.392, 95 %CI: 1.247-1.553) were significantly higher than heatwave alone (e.g., severe HWF only; RR = 1.150, 95 %CI: 1.044-1.268). The effect of severe CDHWs disappeared from subgroups with low to high Water, sanitation and hygiene (WASH) scores. The average excess risk (ER) per hot season attributed to compound drought and HWF increased by 16.4-84.8 % during 2021-2100 under various climate change scenarios. Future CDHW-related ER of childhood diarrhea varied by climate zones and geographic regions. There was a stronger association between CDHW and diarrhea risk than that of heatwave alone, while good WASH had a potential protective effect. Our findings highlight the need of integrated public health and climate adaptation strategies to address the escalating burden of childhood diarrhea associated with compound climate extremes.