Tamil Nadu has the strongest climate signal in India, with each person losing an extra 7.9 hours of sleep per year on warmer nights, new analysis shows.
A new analysis found that India was among the countries hardest hit by heat-related sleep loss, with cities in southern India losing between 78 to 91 hours of sleep annually due to higher night-time temperatures, including 8 to 9 hours due to climate change.
The report, titled Climate Change Costs People (2020-2025) from Climate Central, noted that the burden falls more heavily on the elderly, women, low-income families and those without access to cooling, and is exacerbated by the urban heat island effect in dense cities.
The global average annual heat-related sleep loss in 2020-2025 was calculated at 56 hours, about 10% of which was due to climate change. West Asia topped this chart, with cities in Saudi Arabia, Oman and the United Arab Emirates losing between 12 and 16 hours annually due to climate change. Parts of Southeast Asia and West Africa constitute the next level.
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Big cities are taking a beating
Chennai recorded the highest total loss among major metros at 93 hours per year, followed by Mumbai (84) and Kolkata (80). The assessment found that Delhi lost 66 hours.
At the state level, Tamil Nadu, Kerala, Andhra Pradesh, Karnataka and Telangana recorded the highest amount of sleep loss. Puducherry topped the state/UT list with an average of 92 hours per person per year, followed by Andhra Pradesh (88.6) and Kerala (88.3). Constantly hot and humid nights led to loss of sleep there.
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Where the climate crisis adds up the most
Tamil Nadu showed the strongest signal of climate change, with an additional 7.9 hours of sleep lost per person per year – the highest in the country. It is followed by Karnataka (7.8) and Rajasthan (7.0), although overall losses are lower compared to the southern coastal states.
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Why does heat cost sleep?
Sleep depends on the body cooling itself, and warm nights interfere with this process
High nighttime temperatures reduce sleep duration and quality.
Impacts are strongest in hotter periods, in warmer regions, and among vulnerable groups.
Lack of sleep is linked to poor mood, cognition, productivity, cardiovascular health, and immunity.
Losses accumulate over repeated nights, so even modest discounts accumulate during the hot season.
