Too hot to sleep

Adequate sleep is important for a variety of economic outcomes. We study the relationship between ambient temperatures and human sleep using daily district-level data on sleep duration collected by nearly half a million individual consumer wearable sensors in Germany from 2020 to 2022. Our results illustrate a nonlinear relationship between temperature and sleep duration. Average sleep duration decreases at high temperatures and is unaffected by low temperatures. For instance, we find a small but statistically significant reduction in average sleep duration of 2.8% (12 min and 8 s) on a tropical night (when daily minimum temperature exceeds 20 °C) compared to a mid-temperature night. We document corresponding changes in physical activity (number of daily steps) and vital signs (resting heart rate) at high minimum temperatures, which could represent potential mechanisms for the link between temperature and sleep.