Tamil Nadu, Kerala and Andhra Pradesh lose the most sleep as nights get hotter

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 erode sleep, according to a new global 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. Globally, people lost an average of nearly 56 hours of sleep every year between 2020 and 2025 due to high nighttime temperatures, with more than 10% of that loss directly attributed to climate change driven largely by fossil fuel use and deforestation.Within this global picture, southern India has emerged as one of the regions most affected outside the Middle East. Cities across southern India recorded between 78 and 91 hours of annual sleep loss due to high nighttime temperatures, including eight to nine hours directly attributable to climate change.The report identified Tamil Nadu, Kerala, Andhra Pradesh, Karnataka and Telangana as India's hotspots for heat-related sleep disruption, noting that persistently hot and humid nights are increasingly reducing sleep while climate change is amplifying these losses across some of the country's hottest regions.Among states and union territories, Puducherry recorded the highest annual sleep loss at 92 hours per person, followed by Andhra Pradesh (88.6 hours) and Kerala (88.3 hours). Tamil Nadu ranked fourth with 84 hours of annual sleep loss but emerged as the state most affected by climate change, with an additional 7.9 hours of sleep lost per person every year because of climate-driven warming. Karnataka followed closely with 72 hours, of which 7.8 hours were climate-attributable sleep loss, while Rajasthan recorded seven hours despite experiencing lower overall sleep loss than the southern coastal states.Kerala, which had four cities included in the analysis, recorded an average annual sleep loss of 88.3 hours per person, of which six hours were linked directly to climate change.The study also found that Maharashtra, represented by 22 cities in the dataset, recorded an average annual sleep loss of 76.3 hours, including 5.8 hours attributable to climate change, suggesting that heat-related sleep disruption is widespread across the state. Uttar Pradesh, despite having 11 cities in the analysis, recorded a comparatively lower climate change signal of 4.9 hours, although residents still lost nearly 69 hours of sleep annually because of high nighttime temperatures.Among India's eight major metropolitan cities, Chennai recorded the highest overall sleep loss, with residents losing an average of 93 hours of sleep annually, including five hours directly attributable to climate change. Mumbai followed with 84 hours and Kolkata with 80 hours, reflecting persistently warm and humid nights.Bengaluru stood out for recording the strongest climate change signal among the country's major metros. Residents lose an additional eight hours of sleep every year because of climate change, accounting for nearly 12% of all temperature-related sleep loss in the city. Hyderabad recorded seven additional climate-driven hours of sleep loss annually, while Ahmedabad and Pune each recorded six hours. Delhi had the lowest overall sleep loss among the eight metros at 66 hours a year but still lost an estimated five hours annually due to climate change.The report warned that high overnight temperatures are becoming a growing public health concern because they prevent the body from cooling and recovering from daytime heat. Poor sleep is associated with impaired cognitive performance, poorer mental health, weakened immunity, cardiovascular diseases, reduced productivity, increased risk of accidents and, over time, higher risks of diabetes, hypertension and premature death.The health burden is expected to be particularly severe in India, where millions live in densely populated cities affected by the urban heat island effect, which traps heat and keeps urban areas warmer after sunset. Older adults, women, infants, pregnant women, low-income households and people without access to adequate cooling are among those most vulnerable to heat-related sleep disruption.Globally, the highest climate change-attributable sleep loss was recorded in cities across the Middle East, particularly in Saudi Arabia, Oman and the United Arab Emirates, where residents lost between 55 and 87 hours of sleep annually, including 12 to 16 hours directly linked to climate change. Southern India and parts of Southeast Asia were identified as the next most affected regions, underscoring the growing impact of warming nights on public health.Calling sleep loss a "hidden but growing consequence" of climate change, Climate Central vice president for science Kristina Dahl said the findings show that the impacts of fossil fuel-driven warming extend beyond extreme weather and are now undermining one of the most fundamental requirements for human health. The researchers said the findings highlight the need for stronger adaptation measures to protect vulnerable communities alongside urgent reductions in greenhouse gas emissions.