A comprehensive study published in the journal Environmental International has found that extreme heatwaves are significantly increasing mortality rates across several Indian cities. The study, titled "Impact of Heatwaves on All-Cause Mortality in India: A Comprehensive Multi-City Study," provides strong evidence that prolonged high temperatures are linked to daily mortality increases.

Researchers analyzed data from ten Indian cities—Delhi, Varanasi, Shimla, Ahmedabad, Kolkata, Mumbai, Pune, Chennai, Hyderabad, and Bengaluru. The findings reveal a 12.2% increase in daily mortality when temperatures exceed the 97th percentile for a single day. This rate rises to 14.7%, 17.8%, and 19.4% when such high temperatures persist for two, three, and five consecutive days, respectively. Extreme heatwaves, defined as temperatures higher than 99% of days in a year, can raise mortality rates by up to 33.3% over five days. Cities like Delhi, Ahmedabad, Hyderabad, Kolkata, Varanasi, and Chennai have experienced such conditions.

According to the World Meteorological Organization, a heatwave is a period of local excess heat over several unusually hot days and nights. This study utilized data spanning from 2008 to 2019 for larger cities like Delhi, Chennai, Kolkata, and Mumbai, while data from smaller cities covered 2008 to 2012.

The authors estimated that approximately 1,116 deaths annually across the ten cities were attributable to heatwaves defined as two consecutive days above the 97th percentile. In contrast, 58 deaths were linked to heatwaves lasting at least three consecutive days above the 99th percentile. Higher mortality rates were observed in Delhi, Ahmedabad, and Chennai, while Shimla and Pune had the lowest rates.

Jeroen de Bont, the lead researcher from the Institute of Environmental Medicine at Karolinska Institute, stated, "We wanted to find out how much the risk of death increases during heatwaves."

Dr. Pankaj Kumar, Senior Director of Critical Care at Fortis Hospital, Shalimar Bagh, commented on the study, highlighting the adverse effects of excessive heat on health, including heat stress, reduced physical performance, and increased morbidity and mortality. He emphasized the preventable nature of heat-related deaths, especially given the rising incidence due to climate change.

Dr. M Wali, Sr. Consultant at Sir Ganga Ram Hospital, noted that extreme heat can denature body cell proteins and impair vital organ functions, leading to severe health outcomes, particularly for individuals with pre-existing conditions like diabetes, heart disease, and epilepsy.

Dr. Rajeev Gupta, Director of Internal Medicine at CK Birla Hospital, Delhi, added that extreme heat exacerbates conditions like cardiovascular diseases and respiratory disorders, leading to higher mortality rates. Prolonged exposure to high temperatures can cause organ failure and death, especially in vulnerable populations.

The study underscores the urgent need for effective interventions to mitigate the health impacts of extreme heatwaves, emphasizing the importance of protecting vulnerable groups and improving public awareness and preparedness.