Ambient heat exposure and heatstroke mortality: a state-level spatio-temporal assessment

Increasing temperatures and subsequent heatwaves are significant public health issues in India. Given region-specific variations, temporal, spatial, and statistical associations between heat exposure and heat-related deaths is key to targeted adaptation and prevention measures. The current longitudinal study using secondary data analysed an unbalanced panel dataset comprising temperature indicators, heatwave days, heatwave deaths, and heatstroke mortality in India between 2013 and 2018. Temporal analyses, spatial parameters and bivariate correlations were used to assess interannual variation, risk, and the relationship between heat exposure and mortality. Fixed-effects negative binomial regression models accounted for state- and year-specific heterogeneity. Slight changes in mean temperatures nationwide and significant variations in the number of heatwave days (>37 degrees Celsius), with the highest mortality around 2015. A moderate positive association between the average number of heatwave days and mortality from heatstroke (ρ=0.55, p=0.006) was identified at the state level. Each additional heatwave day was associated with a 19% increase in heatstroke fatalities (IRR=1.19, p<0.001). The spatial heterogeneity in heatwave exposure indicates the need for state-specific heat action plans, including reducing the duration of high-temperature exposure and enhancing early warning and response networks.