Southern states lose the most sleep as nights get hotter, study finds
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India has emerged as one of the world's hotspots for climate-related sleep loss, with southern states recording the highest disruption as rising nighttime temperatures increasingly affect sleep, according to a new analysis by Climate Central.
The study, which examined 1,338 major cities worldwide, found that climate change has at least doubled temperature-related sleep loss since the early 1970s in nearly every city analysed. Between 2020 and 2025, people globally lost an average of nearly 56 hours of sleep each year due to high nighttime temperatures, with more than 10 per cent of that loss directly attributed to climate change.
In India, southern states were among the worst affected outside West Asia. Cities across the region recorded between 78 and 91 hours of annual sleep loss due to hot nights, including eight to nine hours directly linked to climate change.
The report identified Tamil Nadu, Kerala, Andhra Pradesh, Karnataka, and Telangana as the country's hotspots for heat-related sleep disruption.
Among states and Union Territories, Puducherry recorded the highest annual sleep loss at 92 hours per person, followed by Andhra Pradesh at 88.6 hours and Kerala at 88.3 hours. Tamil Nadu ranked fourth with 84 hours of annual sleep loss but recorded the highest climate change impact, with an additional 7.9 hours of sleep lost annually due to climate-driven warming.
Among major cities, Chennai recorded the highest overall sleep loss at 93 hours per year, followed by Mumbai at 84 hours and Kolkata at 80 hours. Bengaluru recorded the strongest climate change impact among the eight major metros, with residents losing an additional eight hours of sleep annually because of climate change.
Hyderabad recorded seven additional climate-related hours, while Ahmedabad and Pune each recorded six hours. Delhi recorded the lowest overall sleep loss among the metros at 66 hours annually, including five hours attributed to climate change.
The report warned that rising nighttime temperatures are becoming a significant public health concern as they prevent the body from cooling and recovering from daytime heat. It said poor sleep is linked to impaired cognitive function, poorer mental health, weakened immunity, cardiovascular disease, lower productivity, and an increased risk of diabetes, hypertension, and premature death.
The study also noted that older adults, women, infants, pregnant women, low-income households, and people without access to adequate cooling are particularly vulnerable to heat-related sleep disruption.