How the Heat is Messing with Your Sleep

Restless nights may become the new norm as temperatures soar worldwide. From San Diego's intense humidity to regions across Southern California, the Southwest, North Africa, the Middle East, and Southern Europe, heat waves are causing billions of people to struggle with sleep. According to a new analysis from climate change nonprofit Climate Central, the average person lost nearly 56 hours of sleep per year due to elevated nighttime temperatures between 2020 and 2025.

Heat makes people sleepy during the day because the body uses energy to regulate temperature, and the cooling process resembles what occurs at night when the body prepares for sleep. However, nighttime heat disrupts sleep by increasing wakefulness and reducing deep and REM sleep, which are crucial for tissue repair, immune support, memory, and emotional regulation. Humidity exacerbates the problem, as dry sweat evaporation hampers natural cooling.

Sleep loss can lead to numerous health issues, such as obesity, heart disease, diabetes, and depression. Since the 1970s, the amount of sleep loss attributable to temperature has doubled or more in cities analyzed by Climate Central. More than 10% of this annual average sleep loss is linked to climate change, and global average temperatures are expected to keep rising over the next five years.

Urbanization also contributes to hotter nights due to the heat island effect, where buildings and roads absorb solar heat. Cities in the Middle East, particularly in Saudi Arabia, Oman, the United Arab Emirates, southern India, Southeast Asia, and West Africa, experienced the worst effects. During the hottest seasons and for vulnerable populations lacking air conditioning, sleep loss is most pronounced. Older adults and women are particularly at risk.

To cope with heatwaves, simple strategies can help manage sleep quality. Close blinds to keep living spaces cool, open windows for cross breezes, avoid heat-generating appliances during peak hours, and choose light bedding. Be cautious with fans, as they evaporate sweat but don't cool the air. While temperature-controlled mattresses may offer some relief, a recent study found limited objective improvement in sleep quality.