Living with 45°C summer: How extreme heat is quietly damaging our heart, kidneys, brain

For decades, extreme heat was treated as a seasonal hardship but temporary. But with large parts of India consistently reporting summer temperatures above 44°C, heat stress is posing a health threat. “We are not looking at dramatic episodes of heatstroke but the quieter, cumulative damage that relentless heat inflicts on the human body over weeks and months. The body gets very little time to recover,” says Dr Rakesh Gupta, senior consultant, Internal Medicine, Indraprastha Apollo Hospital, New Delhi.

Sustained exposure to extreme heat affects nearly every major organ system. It strains the heart, taxes the kidneys, disrupts sleep, impairs cognition, alters emotional stability and accelerates underlying disease. And it does so unevenly, with children, working-age adults and the elderly facing distinct and often underestimated risks.

“The human body was never designed to work continuously to maintain its core temperature. With sustained heat exposure, the body spends more time trying to cool itself through sweating and changes in blood circulation. Over time, this can lead to persistent fluid and electrolyte loss, disturbed sleep, fatigue, reduced concentration, headaches, and a general feeling of exhaustion. People may dismiss these symptoms as routine tiredness, but they can be early signs that the body is struggling to adapt. By the time the body visibly collapses, the damage is often already advanced,” says Dr Gupta.

Dr Prashant Borade, Director-ICU at Gleneagles Hospital, Mumbai, says hospitals are witnessing a sharp rise in patients suffering from severe heat stress and dehydration. “Blood investigations in severe cases often reveal muscle breakdown, strain on the kidneys and liver, and dangerous electrolyte imbalance caused by extreme heat exposure,” he says.