As climate change intensifies, the frequency and severity of heat waves are projected to increase, posing a significant threat to public health worldwide. In India, the world’s largest population, heat waves are a recurring phenomenon, yet their impact on mortality has not been comprehensively studied. This article presents the findings of a groundbreaking study that evaluates the association between heat waves and all-cause mortality, shedding light on the magnitude of the health risks faced by Indian populations.
HEATWAVES AND MORTALITY
Analyzing data encompassing approximately 3.6 million deaths, researchers observed a stark correlation between elevated temperatures and daily mortality rates. Specifically, temperatures exceeding the 97th percentile for two consecutive days were linked to a concerning 14.7% increase in daily mortality. Moreover, alternative definitions of heat waves, characterized by higher percentiles and longer durations, yielded even stronger relative risks, underscoring the severity of the threat posed by extreme heat events.
IMPACT ASSESSMENT: ESTIMATING ATTRIBUTABLE MORTALITY
The study further quantified the attributable mortality fraction associated with heat waves in India, revealing that approximately 1,116 deaths annually can be attributed to these extreme temperature events. Importantly, the burden of heatwave-related deaths varied depending on the definition of heat waves employed, with shorter and less intense criteria resulting in higher estimated mortality rates. These findings underscore the nuanced nature of heat wave impacts and the importance of precise definitions in assessing their health consequences.
CITY-LEVEL ANALYSIS: VARIABILITY IN HEATWAVE EFFECTS
Examining mortality patterns across Indian cities, researchers identified significant disparities in the impact of heat waves on daily deaths. On average, 136 daily deaths were recorded across the cities studied, with wide-ranging variations observed. Cities like Shimla and Delhi experienced the highest daily mortality rates during heat wave events, highlighting the heightened vulnerability of densely populated urban centres to extreme heat.
TEMPORAL TRENDS: FREQUENCY AND INTENSITY OF HEATWAVES
The study also examined temporal trends in heat wave occurrence, revealing an average of three heat waves per year across all cities during the study period from 2008 to 2019. Hyderabad and Pune emerged as hotspots for heat wave activity, experiencing the highest average number of heat waves annually. Additionally, cities like Delhi and Shimla exhibited the highest intensity of heat waves, with temperatures soaring significantly above average daily mean temperatures during these events.
URGENT ACTION NEEDED TO MITIGATE HEALTH RISKS
The findings of this study underscore the urgent need for proactive measures to mitigate the health risks associated with heat waves in India. From implementing heat wave early warning systems to enhancing healthcare infrastructure and promoting heat stress mitigation strategies, concerted efforts are required to safeguard vulnerable populations from the adverse effects of rising temperatures. By prioritizing adaptation and resilience-building initiatives, India can mitigate the impacts of climate change on public health and ensure a safer and more sustainable future for all.
