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Updated: Oct 9, 2025
In vitro Assessment of Myocardial Protection following Hypothermia-Preconditioning in a Human Cardiac Myocytes Model
Published on: October 27, 2020
Cold Weather and Cardiac Arrest in 4 Seasons: Helsinki, Finland, 1997‒2018
Niilo R I Ryti1, Jouni Nurmi1, Ari Salo1
1Niilo R. I. Ryti is with the Center for Environmental and Respiratory Health Research (CERH), Faculty of Medicine, University of Oulu, and Medical Research Center Oulu, University of Oulu and Oulu University Hospital, Oulu, Finland. Jouni Nurmi, Ari Salo, and Markku Kuisma are with the Department of Emergency Medicine and Services, Helsinki University Hospital, Helsinki, Finland. Harri Antikainen is with the Geography Research Unit, University of Oulu. Jouni J. K. Jaakkola is with CERH, Faculty of Medicine, University of Oulu, and Medical Research Center Oulu, University of Oulu and Oulu University Hospital, and the Finnish Meteorological Institute, Helsinki.
Insights
Cold weather increases the risk of out-of-hospital cardiac arrest (OHCA) during all seasons, not just winter. Public health strategies should consider year-round cold weather impacts on OHCA risk.
Area of Science:
- Environmental Health
- Cardiovascular Epidemiology
- Public Health
Background:
- Out-of-hospital cardiac arrest (OHCA) is a critical public health concern.
- Existing cold weather public health strategies primarily focus on winter months.
Purpose of the Study:
- To investigate the association between cold weather and OHCA across all four seasons.
- To test the hypothesis that cold weather is a risk factor for OHCA year-round.
Main Methods:
- A case-crossover design was employed using 22 years of OHCA data from Helsinki, Finland (1997-2018).
- Cold weather was statistically defined for each case and season.
- Conditional logistic regression models were used, stratified by season.
Main Results:
- A significant association was found between cold weather and OHCA during all seasons.
- Each additional cold day elevated OHCA risk by 7% (95% CI: 4%-10%).
- The strength of association was consistent across autumn, winter, spring, and summer.
Conclusions:
- Cold weather is a consistent risk factor for OHCA throughout the year.
- Current public health interventions may underestimate the full impact of cold weather on OHCA mortality.
Abstract:
Objectives. To test the a priori hypothesis that out-of-hospital cardiac arrest (OHCA) is associated with cold weather during all seasons, not only during the winter. Methods. We applied a case‒crossover design to all cases of nontraumatic OHCA in Helsinki, Finland, over 22 years: 1997 to 2018. We statistically defined cold weather for each case and season, and applied conditional logistic regression with 2 complementary models a priori according to the season of death. Results. There was an association between cold weather and OHCA during all seasons, not only during the winter. Each additional cold day increased the odds of OHCA by 7% (95% confidence interval [CI] = 4%, 10%), with similar strength of association during the autumn (6%; 95% CI = 0%, 12%), winter (6%; 95% CI = 1%, 12%), spring (8%; 95% CI = 2%, 14%), and summer (7%; 95% CI = 0%, 15%). Conclusions. Cold weather, defined according to season, increased the odds of OHCA during all seasons in similar quantity. Public Health Implications. Early warning systems and cold weather plans focus implicitly on the winter season. This may lead to incomplete measures in reducing excess mortality related to cold weather. (Am J Public Health. 2022;112(1):107-115. https://doi.org/10.2105/AJPH.2021.306549).
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