Globally, each person has slept an average of 56 fewer hours than desired annually due to nighttime heat. Of these, approximately 10% are directly attributable to the effects of climate change. In Barcelona, this figure rises to 39 fewer hours of rest per person due to high nighttime temperatures, 12% of which are caused by the climate crisis. This equates to nearly five fewer days of rest each year, considering an average of eight hours of sleep per night.
Global warming is impacting sleep quality worldwide. High nighttime temperatures negatively affect the ability to rest properly, with potential health effects such as increased cardiovascular risk or poorer cognitive performance.
The study, which analyzed temperatures in 1,338 cities globally between 1970-1975 and 2020-2025, estimates sleep loss due to heat and the proportion attributable to global warming. Southern Europe, including cities like Naples (51 fewer hours), Athens (45 hours), and Palermo (43 hours), is among the most affected regions. In Milan and Turin, the climate crisis has increased sleep loss by 20% and 19% respectively.
Sleep loss due to climate causes has doubled since the 1970s. While in the 70s climate change accounted for 4% of heat-related sleep loss, this figure now reaches 10%. In Barcelona, 50 years ago, 33 annual hours were lost, with only one (5%) attributed to global warming, whereas now five hours (12%) are attributable to climate change.
Large cities particularly suffer from this phenomenon due to the "urban heat island" effect. Access to mitigation measures like air conditioning is unequal, disproportionately affecting low-income populations and the elderly, who experience double or triple the sleep loss compared to other groups.
