NEW DELHI: India is among the global hotspots for climate-related sleep loss, with people in the country's 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.
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 per cent, 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.
The research has found that across all the 1,338 major global cities analysed, the amount of temperature-related sleep loss linked to climate change has at least doubled since the early 1970s.
"The analysis reveals how climate change is translating into measurable hours of lost sleep for people around the world.
By combining the latest climate attribution science with research on how heat affects sleep, we can now quantify a hidden but growing consequence of rising temperatures," said Kristina Dahl, Climate Central's vice-president for science.
"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," he added.
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, while Bengaluru recorded the strongest climate change signal (eight hours per year).
In Maharashtra, the average annual sleep loss was 76.3 hours, including 5.8 hours linked to climate change.
In Uttar Pradesh, residents lost 69 hours of sleep annually, with 4.9 hours attributable to climate change.
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.
Courtney Howard, MD, Emergency Physician, Chair of the Global Climate and Health Alliance, and President-Elect of the Canadian Medical Association, said, "Adults need seven to nine hours of sleep per night for optimal health. Increases in nighttime temperatures harm human sleep, with a larger effect seen in residents from lower-income countries, older adults and in women."
"Sleeping less than seven hours per night is associated with impaired immune function and performance, and increased errors, pain and accidents. If poor sleep continues on a regular basis, it is associated with weight gain, diabetes, hypertension, cardiovascular disease and increased risk of death," Howard said.
The report said as climate change drives more frequent and intense hot nights, sleep disruption should be recognised as a growing concern for both public health and human productivity.