Overview
- The study, published in The Lancet Global Health, analyzes WHO surveys and Climatic Research Unit temperature data from 156 countries spanning 2000–2022.
- Each additional month with average temperatures above 27.8°C (82°F) is associated with a 1.5 percentage point rise in inactivity globally and 1.85 points in low- and middle-income countries, with no clear effect in high-income nations.
- Modeling projects 470,000 to 700,000 additional premature deaths annually by 2050 linked to heat-driven inactivity, along with US$2.4–3.68 billion in productivity losses.
- The largest increases are projected in Central America, the Caribbean, eastern Sub-Saharan Africa, and equatorial Southeast Asia, with country examples including Somalia at up to 70 deaths per 100,000 and the U.S. around 2.5 per 100,000 by 2050.
- Authors note substantial uncertainty due to self-reported activity data and temperature-only modeling, and they recommend cooler urban design, affordable climate-controlled exercise spaces, targeted heat-risk guidance, workplace protections, and strong emissions reductions.