People losing 65-93 hours of sleep each year in India’s big cities because of high nighttime temperatures: Study

3 min readPuneJul 16, 2026 12:42 AM IST

Unusually high night-time temperatures has emerged as a major concern in recent years, and the cause of many heat-related deaths.

People in some of India’s largest cities are losing between 65 and 93 hours of sleep each year because of climate change-induced increases in night-time temperatures, a new study has revealed.

Chennai was found to be the city with highest overall sleep loss in India, with residents losing an average of 93 hours of sleep annually, of which five hours could be directly attributable to climate change, according to the study by Climate Central, a US-based climate advocacy group. Residents of Mumbai and Kolkata are losing 84 and 80 hours of sleep respectively every year, the study said.

The study used an already-established relationship between night-time temperatures and sleep to assess loss of sleeping hours in more than 1,300 cities across the world. It found that an average person in these cities lost nearly 56 hours of sleep per year in the 2020-2025 time period because of unusually high night-time temperatures. At least 10 per cent of this sleep loss could be directly attributed to human-induced climate change.

Unusually high night-time temperatures has emerged as a major concern in recent years, and the cause of many heat-related deaths. High temperatures at night prevent the human bodies from cooling down and recover from the heat stress experienced during the day, leading to loss of energy, discomfort and lack of productivity during day time. It is also a health hazard, increasing the risk of strokes and other cardiovascular conditions. Short and poor-quality sleep can also shorten life expectancy and increase the risk of accidents and injuries.

Due to climate change, night-time temperatures have increased at a faster rate compared to day-time temperatures across the world.

“Many people have been experiencing hotter summer nights, making it harder for the body to cool down before sleep. As a result, sleep quality suffers, which can lead to irritability, mental and physical fatigue. People living with chronic health conditions are particularly vulnerable to these effects,” Abhiyant Tiwari, lead, climate resilience and health at the Natural Resources Defence Council (NRDC), an environmental advocacy group, said.

The study included over 100 Indian cities, and found substantial losses in sleeping hours everywhere. Delhi and Chandigarh were among the cities where the sleep loss was the lowest, about 67 and 62 hours every year. Bengaluru happened to be the city where the footprint of climate change was observed to be the highest, about 12 per cent of the 67 hours lost every year.

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Anuradha Mascarenhas is a Senior Editor at The Indian Express, based in Pune. With a career spanning three decades, she is one of the most respected voices in Indian journalism regarding healthcare, science and environment and research developments. She also takes a keen interest in covering women's issues .

Professional Background

Education: A gold medalist in Communication and Journalism from Savitribai Phule Pune University and a Master’s degree in Literature.

Author: She authored the biography At The Wheel Of Research, which chronicles the life and work of Dr. Soumya Swaminathan, the former Chief Scientist at the WHO.

Key Focus: She combines scientific accuracy with storytelling, translating complex medical research into compelling public and human-interest narratives.

Awards and Recognition

Anuradha has won several awards including the Press Council of India's national award for excellence in journalism under the gender based reporting category in 2019 and the Laadli Media award (gender sensitivity -2024). A recipient of the Lokmat journalism award (gender category-2022), she was also shortlisted for the RedInk awards for excellence in journalism-2021. Her debut book At The Wheel Of Research, an exclusive biography of Dr Soumya Swaminathan the inaugural chief scientist of World Health Organisation was also nominated in the Popular Choice Category of JK Paper AUTHER awards. She has also secured competitive fellowships including the Laadli Media Fellowship (2022), the Survivors Against TB – New Research in TB Media Fellowship (2023) and is part of the prestigious 2025 India Cohort of the WomenLift Health Leadership Journey.”

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Anuradha is known for her COVID-19 reportage, where she was one of the first journalists to provide detailed insights into the Covishield and Covaxin trials. She has a dedicated interest in gender diversity in health and science, often profiling women researchers who are breaking the "leaky pipeline" in STEM fields. Her writing style is scrupulous, often featuring interviews with top-tier scientists and health experts from various institutions.

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