Cardiovascular

Associations Between Acute Heat Exposure and Hospitalization for Takotsubo Syndrome in the State of California, 2006 to 2019.

Hao H, Zhang Y, et al. • Journal of the American Heart Association • 2026

PubMed 42179263 DOI 10.1161/JAHA.125.047065

TL;DR

Short-term exposure to heat waves is associated with increased risk of TTS hospitalizations, particularly at lag days 4-6, with stronger associations among women and individuals ≤65 years.

Key Findings

Results

Heatwave exposure was significantly associated with elevated odds of Takotsubo Syndrome hospitalization, with the strongest association observed at lag day 5.

OR for lag 5: 1.382 (95% CI, 1.167–1.636)
OR for cumulative lag 4–6: 1.300 (95% CI, 1.142–1.479)
Heatwaves were defined as ≥2 consecutive days exceeding the ZIP code-specific 95th percentile of daily maximum temperature
Peak heat wave temperatures were on average 4.21°C higher than pre-heat wave days

Methods

A total of 5,018 TTS hospitalization events were identified across California from 2006 to 2019.

Data were drawn from statewide emergency department and hospitalization records in California over a 14-year period
TTS was identified using ICD-9-CM code 429.83 and ICD-10-CM code I51.81
Four case definitions were used, incorporating primary versus secondary diagnosis and procedural criteria
A time-stratified case-crossover design with conditional logistic regression was employed

Results

Subgroup analyses revealed stronger associations between heatwave exposure and TTS hospitalization among women compared to men.

Subgroup analyses showed stronger associations among women
This is consistent with the known predominance of TTS in female populations
Models adjusted for dew point temperature, day of year, and holidays

Results

Individuals aged 65 years or younger showed stronger associations between heatwave exposure and TTS hospitalization than older individuals.

Subgroup analyses showed stronger associations among individuals ≤65 years
This finding was notable given that TTS is generally more common in older populations
The finding suggests age-specific vulnerability patterns to heat-triggered cardiac stress responses

Results

The association between heat exposure and TTS hospitalization followed a delayed pattern, emerging several days after heat wave onset rather than immediately.

The strongest association was observed at lag days 4–6, not at lag day 0 or 1
OR at lag 5 was 1.382 (95% CI, 1.167–1.636)
This delayed response may reflect cumulative physiological stress mechanisms triggered by sustained heat exposure
A time-stratified case-crossover analysis was used to account for individual-level confounding

Conclusions

The authors conclude that targeted surveillance and preventative strategies are needed during periods of extreme heat, particularly among susceptible subpopulations.

Findings underscore the need for targeted surveillance during extreme heat periods
Susceptible subpopulations identified include women and individuals ≤65 years
Although psychosocial factors are well-established TTS triggers, the study adds environmental heat as an additional precipitating factor
The study spans 2006–2019, a period with increasing frequency of extreme heat events

What This Means

This research suggests that extreme heat events — specifically heat waves lasting at least two consecutive days — are linked to a significantly higher risk of being hospitalized for Takotsubo Syndrome (TTS), sometimes called 'broken heart syndrome.' TTS is a temporary but serious heart condition where the heart's main pumping chamber suddenly weakens, often triggered by intense stress. Using 14 years of hospital data from California and over 5,000 TTS cases, researchers found that the risk of hospitalization was about 30–38% higher in the days following a heat wave, with the peak risk appearing 4 to 6 days after heat wave onset rather than immediately — suggesting the body's response to heat stress builds up over several days. The study also found that the heat-TTS link was stronger in women and in people aged 65 and under, which is somewhat surprising given that TTS is already more common in older women. This points to the possibility that younger individuals or those with certain vulnerabilities may be particularly at risk during extreme heat. The heat waves studied were, on average, about 4.2°C hotter than the days before them, representing significant thermal stress beyond local norms. This research matters because climate change is increasing the frequency and intensity of heat waves globally. The findings suggest that extreme heat should be recognized as an environmental trigger for serious cardiac events, not just a comfort or hydration issue. Public health efforts during heat emergencies — such as cooling centers, early warning systems, and outreach to at-risk groups — may have benefits for heart health beyond what was previously understood.

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Citation

Hao H, Zhang Y, Zhu Q, Cheng S, Zhang R, Liu Y, et al.. (2026). Associations Between Acute Heat Exposure and Hospitalization for Takotsubo Syndrome in the State of California, 2006 to 2019.. Journal of the American Heart Association. https://doi.org/10.1161/JAHA.125.047065

Key Findings

What This Means

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