People Lose Seven Nights of Rest to Hotter Nights: Report

A new report by Climate Central found that climate change is causing a sleep deficit globally with people losing 56 hours of sleep every year due to rising nighttime temperatures. The report said an estimated six hours of that annual sleep loss, or just over 10%, can be attributed to warming caused by climate change. That is equivalent to nearly seven nights’ worth of sleep lost each year due to higher nighttime temperatures, including about one night linked to climate change.

The report analysed temperature data from 1,338 global cities worldwide between 2020 and 2025. In the early 1970s, inhabitants of the average city 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 climate change-linked portion of this sleep loss has at least doubled since the early 1970s in nearly every city and has at least tripled in 840 of those cities, the report found. 

Southern India Among The Worst Affected Regions

While cities in the Middle East recorded the highest climate-linked sleep losses globally, South India also emerged as one of the most severely affected regions. According to the analysis, residents in southern India and parts of Southeast Asia lost 78 to 91 hours of sleep annually due to warmer nights, with eight to nine hours of that loss linked specifically to climate change.

The report attributed the disproportionate impact to already warm nighttime temperatures, which leaves little room for further warming before sleep quality begins to decline.

Health Risk Extend Beyond Tiredness

The report noted that sleep is critical for physical and mental health, influencing mood, cognitive performance, productivity, cardiovascular health, and immune function. Hotter nights interfere with the body's natural cooling process, making it harder to fall asleep and remain asleep.

Although many factors affect sleep, including stress, work schedules, caffeine, humidity, and room conditions, the researchers argued that climate change is becoming an increasingly significant environmental risk as global temperatures continue to rise. 

The report said rising nighttime temperatures represented a growing public health issue that often received less attention than daytime heat. As cities continued to warm and urbanisation intensified the urban heat island effect, the cumulative loss of sleep could have wider implications for public health, labour productivity, and overall well-being. 

Vulnerable Population Faces Greater Burden of Sleep Deficit

The report warned that the effects of nighttime heat are not evenly distributed. The analysis citing a study showed that adults over 65 experience more than twice the sleep disruption of middle-aged adults, while people living in lower-middle-income countries are nearly three times more affected than those in wealthier nations. Women and people already living in hotter climates also face greater risks.

Air conditioning can reduce exposure to hot nights, but access remains highly unequal and closely linked to income. Globally, only about 35% of households owned air conditioners in 2021, leaving many people in hot regions with limited protection. The report also noted that even where cooling is available, hotter nights can still reduce sleep quality.