Climate change has at least doubled the temperature-related sleep loss across 1,338 major cities worldwide over the past five decades, highlighting an emerging but often overlooked public health consequence of rising global temperatures. A new study by Climate Central estimates that between 2020 and 2025, the average person globally lost nearly 56 hours of sleep each year because of elevated night-time temperatures. More than 10% of this sleep loss-around six hours annually is directly attributable to human-caused climate change driven primarily by fossil fuel emissions and deforestation.

 

The analysis combines climate attribution science with established research linking night time temperatures to reduced sleep duration, making it the first global assessment to quantify sleep loss directly attributable to climate change.

 

India has emerged as one of the countries most affected by climate-related sleep disruption, with southern states recording some of the highest levels of temperature-related sleep loss outside the Middle East.

 

Residents across southern India lose between 78 and 91 hours of sleep annually because of high night time temperatures, including 8-9 hours directly attributable to climate change.

 

The findings underscore the growing health burden posed by increasingly warm nights, particularly in India's densely populated cities where urban heat island effects further amplify night time temperatures.

 

Southern India records the highest levels of temperature-related sleep disruption.

 

· Puducherry records the country's highest annual sleep loss at 92 hours per person.

 

· Andhra Pradesh follows with 88.6 hours of annual sleep loss.

 

· Kerala records 88.3 hours annually.

 

· Tamil Nadu experiences the highest climate change-attributable sleep loss in India, with 7.9 additional hours per person annually.

 

· Karnataka records 7.8 climate-attributable hours, while Rajasthan records 7.0 hours, despite comparatively lower overall sleep loss.

 

Among larger states:

 

· Maharashtra, represented by 22 cities in the analysis, records an average of 76.3 hours of annual sleep loss, including 5.8 hours attributable to climate change, indicating widespread heat-related sleep disruption.

 

· Uttar Pradesh, covering 11 cities, records nearly 69 hours of annual sleep loss, including 4.9 climate change-attributable hours.

 

Major Indian cities face significant sleep loss

India's largest metropolitan areas lose between 65 and 93 hours of sleep annually because of elevated night time temperatures.

 

Among the major cities:

 

· Chennai records the highest overall annual sleep loss at 93 hours.

 

· Mumbai loses 84 hours annually.

 

· Kolkata records 80 hours.

 

The strongest climate change signal, however, is observed in Bengaluru, where residents lose eight additional hours of sleep annually directly because of climate change, representing nearly 12% of all temperature-related sleep loss.

 

Other cities include:

 

· Hyderabad – 7 climate-attributable hours annually

 

· Ahmedabad – 6 hours

 

· Pune – 6 hours

 

· Delhi – 66 hours of total annual sleep loss, including 5 hours linked directly to climate change

 

The report finds that climate-related sleep disruption has intensified across nearly every region of the world.

 

The greatest impacts were recorded in:

 

· Middle East: Cities across Saudi Arabia, Oman and the United Arab Emirates recorded the highest climate-related sleep losses globally, with 12–16 hours annually directly attributable to climate change.

 

· South India and Southeast Asia: Residents lose 78–91 hours annually, including 8–9 climate-driven hours.

 

· West Africa: Cities in Niger, Nigeria and Burkina Faso lose more than 65 hours annually, with 10–11 hours attributable to climate change.

 

· Americas: Climate-related sleep losses are evident across the U.S. Southwest, Mexico, Central America and northern South America. Across 253 U.S. cities, residents lose an average of 36 hours annually, including about four hours directly attributable to climate change.

 

The analysis shows climate change is becoming an increasingly important driver of night time heat and sleep disruption.

 

Since the early 1970s:

 

· Climate change-attributable sleep loss has increased from around two hours annually to approximately five hours globally.

 

· The climate contribution has at least doubled in 1,335 of the 1,338 cities studied.

 

· It has at least tripled in 840 cities.

 

· In the United States, climate-related sleep loss has nearly tripled—from just over one hour annually in the early 1970s to about four hours today.

 

Sleep plays a vital role in physical and mental recovery, and the body's ability to cool during the night is essential for healthy sleep. Rising night time temperatures interfere with this natural cooling process, leading to shorter sleep duration and poorer sleep quality.

 

According to the report, inadequate sleep caused by hotter nights is associated with:

 

· Reduced cognitive performance

 

· Poor mental health

 

· Lower productivity

 

· Weakened immune function

 

· Cardiovascular disease

 

· Hypertension and diabetes

 

· Increased risks of accidents and injuries

 

· Developmental impacts on children

 

Because sleep deprivation accumulates over consecutive nights, prolonged periods of elevated night time temperatures could significantly increase long-term health risks.

 

Those most at risk include:

 

· Older adults

 

· Infants and young children

 

· Pregnant women

 

· Women

 

· Lower-income households

 

· People living in already hot climates

 

· Communities without reliable access to cooling

 

The report notes that while air conditioning can reduce night time heat exposure, only about 35% of households worldwide had access to air conditioning in 2021, leaving many populations in South Asia, Africa and other lower-income regions particularly vulnerable.

 

Dr. Kristina Dahl, Vice President for Science at Climate Central, described sleep disruption as a ‘hidden but growing consequence’ of climate change saying the findings demonstrate how fossil fuel-driven warming is undermining one of the most fundamental requirements for human health-adequate sleep.

 

Dr. Courtney Howard, Emergency Physician and Chair of the Global Climate and Health Alliance, said adults require seven to nine hours of sleep for optimal health, warning that continued sleep disruption from hotter nights could increase chronic disease risks, reduce productivity and place additional strain on public health systems.

 

The analysis combined established research linking night time temperatures with sleep duration, daily minimum temperature data from ERA5 Reanalysis, and Climate Central's Climate Shift Index (CSI), which estimates temperatures in a world without human-induced climate change.

 

Researchers compared observed temperatures with these counterfactual temperatures across 1,338 cities worldwide with populations exceeding 500,000, as well as 253 U.S. cities, to estimate the amount of sleep loss directly attributable to climate change.

 

The findings position sleep disruption as an emerging and measurable public health impact of climate change. With night time temperatures projected to continue rising, particularly across already hot urban regions, climate-related sleep loss is expected to worsen.

 

For India, especially its southern states and rapidly urbanising cities, the report highlights  urgent need for climate adaptation, heat-resilient urban planning, equitable access to cooling, and accelerated reductions in greenhouse gas emissions to protect public health.