A new study led by Chinese scientists has found that loss of sleep, particularly among children, due to rising heat driven by climate change may deepen global inequality and lead to economic losses.

The study was published last Friday in Nature Sustainability, a subsidiary of the science journal Nature. Researchers from Nanjing University led the study, with collaborators from the Chinese Academy of Environmental Planning; Harvard University and the University of Chicago in the U.S.; and Monash University in Australia.

Excessively hot temperatures can decrease sleep quality and duration, with the ideal temperature range for human sleep falling between 15 and 19 degrees Celsius, according to research. Children are particularly vulnerable to heat, and insufficient sleep can impair memory, attention, intelligence, and cognitive processing speed, ultimately affecting their future earning potential.

Researchers ran simulations covering 198 countries and regions, drawing on multiple datasets and models, including one that tracked individuals’ sleep-state data via wristband sensors alongside external temperature data. 

Under a high-emissions scenario, in which global temperatures rise by around 4 degrees Celsius above pre-industrial levels, people could lose an average of 16.37 hours of sleep annually, compared with the 2000s.

By contrast, under the best-case scenario aligned with the Paris Agreement’s target of a maximum 2 degrees Celsius increase in global warming, annual sleep loss would fall to 3.42 hours.

By examining how changes in average sleep duration could shift IQ distribution in children ages 5 to 14 and then calculating productivity losses based on IQ declines, the researchers estimate that the potential global economic cost of sleep deprivation could amount to trillions of dollars.

Further analysis showed the greatest potential sleep loss in the Middle East, Southeast Asia, and Africa, with smaller impacts in Europe and Oceania. Under a high-emissions scenario, for example, Iceland could lose about 4.5 hours per person annually, while parts of the Middle East and Southeast Asia may exceed 20 hours.

This suggests that many less-developed regions may bear “several times” the relative economic burden of wealthier regions. In other words, places that have contributed less to global warming may end up paying more of the long-term price.

The researchers say their findings could help inform fairer climate policy by cutting emissions and improving nighttime cooling, housing conditions, and heat adaptation for children in more vulnerable regions.

Last year ranked among the hottest years on record and extended a trend of rising global temperatures, according to the World Meteorological Organization. Between May and July 2026, the likelihood of an El Niño — a periodic warming of the central and eastern Pacific that drives up global temperatures — is expected to increase, potentially bringing even more extreme heat.

2012 to 2021 was China's warmest decade on record, which was followed by continued increases in average summer temperatures. Official data reported a new high in 2022, which was surpassed again in 2024 and 2025.

Editor: Marianne Gunnarsson.

(Header image: Visuals from VCG, reedited by Sixth Tone)