Among Medicare beneficiaries, colder ambient temperatures were associated with increased heart failure hospitalizations, whereas warmer temperatures were not, so the U-shaped temperature-cardiovascular risk association described for cardiovascular mortality did not apply for HF hospitalizations among older adults in the US.
Key Findings
Results
Colder ambient temperatures were associated with increased HF hospitalizations among older US Medicare beneficiaries nationally.
Time-stratified case-crossover design using Medicare claims for adults aged ≥65 years hospitalized for HF between January 1, 2007, and December 31, 2022.
Reference temperature was 75 °F, with a 14-day lag for mean temperatures below 75 °F, modeled with conditional logit distributed lag nonlinear models.
Cases were ED visits leading to HF hospitalization, matched to up to 4 control (nonevent) days for the same patient on day of week, month, and year.
Results
Study population comprised 1,517,756 HF hospitalizations from 996,312 older patients.
Mean (SD) age was 78.0 (8.2) years.
60.3% of patients were female.
Daily mean temperature was derived from the PRISM model and linked through residential zip code.
Results
The strongest cold-related associations occurred in the West North Central region, with an OR of 1.62 at the regional fifth percentile temperature versus 75 °F.
West North Central: n = 17,286 (1.1%); OR, 1.62; 95% CI, 1.25-2.11.
Comparison was at the regional fifth percentile temperature versus the 75 °F reference.
Results
Other western and southwestern regions also showed large cold-related associations with HF hospitalization.
West: n = 107,911 (7.1%); OR, 1.40; 95% CI, 1.28-1.53.
Southwest: n = 30,536 (2.0%); OR, 1.34; 95% CI, 1.11-1.62.
Northwest: n = 33,353 (2.2%); OR, 1.34; 95% CI, 1.08-1.65.
Results
Temperatures above 75 °F were not associated with increased HF hospitalization.
Heat analyses used a 0-day lag for mean temperatures greater than 75 °F.
Abstract states warmer temperatures were not associated with increased HF hospitalization.
Conclusions
The U-shaped temperature-risk relationship seen for cardiovascular mortality did not apply to HF hospitalizations in older US adults.
Risk increased with cold but not with heat.
Authors suggest ongoing region-specific surveillance of heat- and cold-related HF hospitalization risk is needed, particularly in areas with limited adaptive capacity.
Results
Associations were estimated separately across 9 climate regions, showing regional heterogeneity in cold-related HF hospitalization risk.
Regions: Central, East North Central, Northeast, Northwest, South, Southeast, Southwest, West, West North Central.
The largest associations were in the West North Central, West, Southwest, and Northwest regions.
What This Means
This study looked at more than 1.5 million hospitalizations for heart failure among Americans aged 65 and older on Medicare from 2007 to 2022. For each patient, researchers compared the temperature on the day they went to the hospital with temperatures on other days in the same month, day of week and year, to see whether temperature was linked to hospitalization.
The research suggests that colder temperatures were linked to more heart failure hospitalizations, while hot temperatures above 75 °F were not. This differs from earlier work on cardiovascular deaths, where both cold and heat raised risk. The cold-related link was strongest in some regions, such as the West North Central, West, Southwest and Northwest, where very cold days (the regional 5th percentile) were associated with roughly 34% to 62% higher odds of hospitalization compared with a mild 75 °F day.
These findings may help guide climate adaptation and health planning, suggesting that attention to cold exposure and regional differences matters for older adults with heart failure. The study is observational, so it shows an association rather than proving cold causes hospitalizations. The authors say continued region-specific monitoring of both heat and cold risks is needed, especially in areas with limited capacity to adapt.
Kuhrt N, Parthasarathi A, Bisno D, Josey K, Gandhi P, Rua M, et al.. (2026). Ambient Temperature and Heart Failure Hospitalizations in Older Adults in the US.. JAMA network open. https://doi.org/10.1001/jamanetworkopen.2026.41051