The recent heatwave across the United Kingdom has intensified concerns over health risks, particularly in relation to widespread sleep disruption. A poll of 2,135 adults conducted by YouGov on behalf of Greenpeace found that two-thirds of respondents experienced significant difficulties sleeping during the last spell of prolonged high temperatures. Nearly half reported losing at least three hours of sleep each night amid tropical overnight conditions where temperatures remained above 20°C.
Experts warn that the upcoming heatwave, forecast to persist for at least 10 days, could exacerbate the ongoing sleep deprivation problem. The resulting lack of rest is linked to various negative health outcomes, including impaired cognitive function, weakened immune responses, and an increased likelihood of accidents. A scientific review published earlier this year highlighted that certain groups—including shift workers, labourers in petrochemical and steel industries, older adults, women, and low-income residents of urban heat islands—are particularly vulnerable to the effects of heat-induced sleep loss.
Analysis of data from wearable health devices indicates that each 1°C increase in nighttime temperatures corresponds to a loss of seven to 14 minutes of sleep daily, with more severe impacts observed in those at greater risk. Occupational heat stress has also been associated with dehydration, kidney dysfunction, reduced productivity, and a higher incidence of workplace accidents.
Emergency response services have noted a rise in heat-related incidents amid the recent heatwave. Air ambulance crews in Hampshire and the Isle of Wight, who usually attend emergencies including major trauma and serious medical conditions, recorded an uptick in calls. Likewise, the South Western Ambulance Service reported its busiest day on record during the hottest June day ever recorded in the UK, handling cases ranging from critical emergencies to sunburn and dehydration.
Physiological factors contribute to the disruption of sleep during hot nights. The body normally promotes sleep by increasing melatonin production and cooling core temperature through blood vessel dilation near the skin’s surface, enabling heat loss. However, when external temperatures remain high, this cooling mechanism becomes less efficient. Humidity further impedes sweat evaporation, leading to discomfort and difficulty falling and staying asleep—even after cooling measures such as cold showers.
As the UK faces increasing occurrences of extreme heat, understanding these effects and identifying protective measures is critical to mitigating the broader impacts on public health and workforce productivity.