Sweden: Temp extremes up heart failure risk

A study published in _JACC_ and presented at ESC Congress 2026 found that short-term exposure to extreme temperatures increases heart failure hospitalization risk in Sweden.

Study Design and Population

Researchers analyzed 482,000 heart failure hospitalizations recorded in the Swedish National Patient Register from 2006 to 2021. Cold spells were defined as two or more consecutive days with temperatures at or below the 5th percentile for October through March, while heat waves were defined as temperatures at or above the 95th percentile for April through September, using municipality-specific thresholds.

Key Findings

• Cold spells were associated with a higher risk of hospitalization within two to six days, with statistical significance observed between three and five days after exposure.
• Lower ambient temperatures also increased hospitalization risk within three to six days, reaching significance in the same window.
• Higher temperature exposure was linked to increased risk within zero to three days.
• No significant association was found between heat wave exposure and heart failure hospitalization.

Clinical Implications

The delayed risk following cold exposure and the immediate risk during heat events suggest that clinical monitoring should be timed accordingly. Authors emphasize the need for early-warning systems and rapid response strategies to mitigate the impact of temperature extremes on heart failure patients.

Expert Commentary

Tiantian Li, Ph.D., deputy director of the National Institute of Environmental Health at the Chinese Center for Disease Control and Prevention, noted that cardiovascular medicine can no longer be practiced without considering meteorological factors. "We can no longer practice cardiovascular medicine in a meteorological vacuum," Li said, calling for the translation of these data into actionable early-warning capabilities.

The study fills a critical knowledge gap by examining short-term temperature effects in a high-latitude Nordic population, where cold exposure is frequent and heat vulnerability is emerging as the climate warms.

Temperature extremes raise heart failure hospitalization risk in Sweden

A study published in _JACC_ and presented at ESC Congress 2026 found that short-term exposure to extreme temperatures increases heart failure hospitalization risk in Sweden.

**Study Design and Population**

Researchers analyzed 482,000 heart failure hospitalizations recorded in the Swedish National Patient Register from 2006 to 2021. Cold spells were defined as two or more consecutive days with temperatures at or below the 5th percentile for October through March, while heat waves were defined as temperatures at or above the 95th percentile for April through September, using municipality-specific thresholds.

**Key Findings**

• Cold spells were associated with a higher risk of hospitalization within two to six days, with statistical significance observed between three and five days after exposure.
• Lower ambient temperatures also increased hospitalization risk within three to six days, reaching significance in the same window.
• Higher temperature exposure was linked to increased risk within zero to three days.
• No significant association was found between heat wave exposure and heart failure hospitalization.

**Clinical Implications**

The delayed risk following cold exposure and the immediate risk during heat events suggest that clinical monitoring should be timed accordingly. Authors emphasize the need for early-warning systems and rapid response strategies to mitigate the impact of temperature extremes on heart failure patients.

**Expert Commentary**

Tiantian Li, Ph.D., deputy director of the National Institute of Environmental Health at the Chinese Center for Disease Control and Prevention, noted that cardiovascular medicine can no longer be practiced without considering meteorological factors. "We can no longer practice cardiovascular medicine in a meteorological vacuum," Li said, calling for the translation of these data into actionable early-warning capabilities.

The study fills a critical knowledge gap by examining short-term temperature effects in a high-latitude Nordic population, where cold exposure is frequent and heat vulnerability is emerging as the climate warms.