Rising nighttime temperatures driven by climate change are quietly robbing people of sleep worldwide, a new study has found.
The analysis, conducted by Climate Central, showed that hotter nights cause the average person to lose nearly 56 hours of sleep per year between 2020 and 2025.
Examining data from 1,338 cities globally, the study found that warmer nighttime conditions have created a sleep deficit equivalent to nearly seven full nights of rest annually. Of that total, more than six hours per person—roughly 10%—can be directly attributed to climate change.
The report also found that the impact of global warming on sleep has intensified over time. Heat-related sleep loss linked to climate change has at least doubled since the early 1970s in 1,335 of the 1,338 cities analyzed, and has at least tripled in 840 of those cities.
“In the early 1970s, inhabitants of the average city we analyzed lost about 46 hours of sleep per year due to nighttime heat. By the 2020s, that rose to about 50 hours, and climate change accounts for a larger share of that burden,” the report said.
Researchers used climate attribution models alongside established physiological sleep–temperature response functions to isolate the effects of human-driven warming on nighttime heat.
“Climate change and nighttime warming are increasingly impinging on the ability to get a good night’s sleep,” the authors said.
Scientists explained that higher nighttime temperatures disrupt the body’s natural cooling process, which is essential for quality sleep.
TROPICAL NIGHTS AROUND THE GLOBE
The report also highlighted regional disparities, with the heaviest burden falling on already hot regions.
In South Asia and parts of Southeast Asia, including India, people lost between 78 and 91 hours of sleep per year due to nighttime heat, with around eight to nine hours linked to climate change.
Cities in the Middle East—including Saudi Arabia, Oman, and the United Arab Emirates—recorded some of the highest losses globally, with residents losing 55 to 87 hours of sleep annually, including 12 to 16 hours directly tied to climate change.
In West Africa, residents of Niger, Nigeria, and Burkina Faso lost 65 or more hours of sleep each year, with 10 to 11 hours attributed to climate change.
In the United States, data from 253 cities showed residents lost an average of 36 hours of sleep annually due to nighttime heat, with about four hours linked to climate change—a figure that has roughly tripled since the 1970s, driven by spikes in states such as Arizona, California, Florida, and Nevada.
The study also found that the effects of warmer nights are not evenly distributed. Other research cited in the report shows that sleep disruption is more than twice as severe for adults over 65 compared to middle-aged adults, and nearly three times greater for people in lower-middle-income countries than those in high-income nations.
“The same study also found greater effects among women and people already living in hotter climates, with heat-related sleep loss likely to worsen as temperatures continue to rise,” the report said.
Public health experts warn that chronic sleep deprivation can lead to serious consequences, including impaired cognitive performance, reduced productivity, weakened immune function, and increased risks of cardiovascular disease and mood disorders.
The report also noted that while air conditioning can help mitigate the effects of nighttime heat, access remains uneven. A 2021 dataset showed that only about 35% of households worldwide have air conditioning, with availability strongly tied to income and “highly unequal” in many hot regions, particularly in South Asia and Africa.
“Even so, hotter nights can still cut into sleep, even in higher-income settings where cooling is more likely to be available,” the report said.
While Climate Central acknowledged that factors such as work schedules, stress, health, caffeine intake, light exposure, noise, and bedroom conditions also affect sleep, the analysis underscored that rising nighttime temperatures due to climate change are a significant and growing contributor to sleep loss.
