Chennai tops Indian cities in sleep loss due to nighttime heat

NEW DELHI: India has emerged among the global hotspots for climate-related sleep loss, with people in the southern parts losing 78 to 91 hours of sleep annually, including eight to nine hours due to climate change, according to a new report by Climate Central.

The analysis covered 107 Indian cities, with Tamil Nadu recording the highest climate change-driven sleep loss (7.9 additional hours per person annually). Chennai (93 hours), Mumbai (84 hours) and Kolkata (80 hours) registered the highest overall sleep loss among major metros.

Globally, an average person lost nearly 56 hours of sleep each year due to nighttime heat between 2020 and 2025. That is equivalent to nearly seven nights’ sleep lost each year due to higher nighttime temperatures, including about one night linked to climate change. The report pointed out that an estimated six hours of the annual sleep loss, or just more than 10%, can be attributed to warming caused by climate change.

Although climate change accounted for a relatively-modest share of the total estimated heat-related sleep loss globally, its influence was substantially stronger in some regions and cities. The largest impacts were concentrated in places that have already experienced extremely warm nighttime temperatures.

“Across more than 1,300 cities, climate change has at least doubled temperature-related sleep loss since the early 1970s, showing that the impacts of fossil fuel-driven warming extend beyond extreme weather to undermine one of the most fundamental requirements for human health,” said Kristina Dahl, Climate Central’s vice-president for science.

Rising night-time temperatures are emerging as a public-health threat, with poor sleep linked to cardiovascular disease, poorer mental health, weakened immunity and reduced productivity, according to Courtney Howard, MD, Emergency Physician, chair of the Global Climate and Health Alliance, and president-elect of the Canadian Medical Association.