Cooler days, not heat, linked to more heart-failure hospitalisations among older Americans

Climate-and-heart research usually focuses on heat waves. A new observational study in JAMA Network Open (first author Nathaniel Kuhrt, Thomas Jefferson University) points to the cold side, TCTMD reported on 31 October 2026.

The study

Researchers analysed 1,517,756 heart-failure hospitalisations among 996,312 Medicare patients (mean age 78; 60.3% women) from 2007 to 2022, comparing daily average temperatures with a reference of 75°F (about 24°C) and adjusting for air pollution and humidity.

Findings

• Compared with 75°F, cooler temperatures at the 5th and 25th percentiles were linked to higher cumulative 14-day odds of heart-failure hospitalisation: odds ratios 1.12 and 1.16.
• Associations were strongest in the West North Central (OR 1.62), West (1.40), Southwest (1.34) and Northwest (1.34) regions.
• Temperatures above 75°F were not linked to more admissions; in the South, the very hottest days were associated with a slight reduction (OR 0.95).

In an accompanying editorial, University of Pennsylvania researchers noted that cold narrows blood vessels and raises blood pressure and the heart’s oxygen demand, and that frequent moderate cold may carry more cumulative risk than rare extreme cold events.

Limitations

The study is observational and cannot prove that cold causes hospitalisations. It covers only older Medicare patients, so results may not apply to younger people; it uses ambient temperature, which may not capture actual heat or cold stress; and it relies on claims data. People with heart failure who have questions about seasonal risks or their medicines should talk to their doctor.