University of Oulu

Vaičiulis, V., Jaakkola, J.J.K., Radišauskas, R. et al. Risk of ischemic and hemorrhagic stroke in relation to cold spells in four seasons. BMC Public Health 23, 554 (2023).

Risk of ischemic and hemorrhagic stroke in relation to cold spells in four seasons

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Author: Vaičiulis, Vidmantas1,2; Jaakkola, Jouni J. K.3,4,5,6; Radišauskas, Ričardas1,7;
Organizations: 1Faculty of Public Health, Department of Environmental and Occupational Medicine, Lithuanian University of Health Sciences, Kaunas, Lithuania
2Faculty of Public Health, Health Research Institute, Lithuanian University of Health Sciences, Kaunas, Lithuania
3Center for Environmental and Respiratory Health Research (CERH), Research Unit of Population Health, Faculty of Medicine, University of Oulu, Oulu, Finland
4Biocenter Oulu, University of Oulu, Oulu, Finland
5Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland
6Finnish Meteorological Institute, Helsinki, Finland
7Laboratory of Population Studies, Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.1 MB)
Persistent link:
Language: English
Published: Springer Nature, 2023
Publish Date: 2023-09-07


Background: Cold winter weather increases the risk of stroke, but the evidence is scarce on whether the risk increases during season-specific cold weather in the other seasons. The objective of our study was to test the hypothesis of an association between personal cold spells and different types of stroke in the season-specific context, and to formally assess effect modification by age and sex.

Methods: We conducted a case-crossover study of all 5396 confirmed 25–64 years old cases with stroke in the city of Kaunas, Lithuania, 2000–2015. We assigned to each case a one-week hazard period and 15 reference periods of the same calendar days of other study years. A personal cold day was defined for each case with a mean temperature below the fifth percentile of the frequency distribution of daily mean temperatures of the hazard and reference periods. Conditional logistic regression was applied to estimate odds ratios (OR) and 95% confidence intervals (95% CI) representing associations between time- and place-specific cold weather and stroke.

Results: There were positive associations between cold weather and stroke in Kaunas, with each additional cold day during the week before the stroke increases the risk by 3% (OR 1.03; 95% CI 1.00–1.07). The association was present for ischemic stroke (OR 1.05; 95% CI 1.01–1.09) but not hemorrhagic stroke (OR 0.98; 95% CI 0.91–1.06). In the summer, the risk of stroke increased by 8% (OR 1.08; 95% CI 1.00–1.16) per each additional cold day during the hazard period. Age and sex did not modify the effect.

Conclusions: Our findings show that personal cold spells increase the risk of stroke, and this pertains to ischemic stroke specifically. Most importantly, cold weather in the summer season may be a previously unrecognized determinant of stroke.

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Series: BMC public health
ISSN: 1471-2458
ISSN-E: 1471-2458
ISSN-L: 1471-2458
Volume: 23
Issue: 1
Article number: 554
DOI: 10.1186/s12889-023-15459-4
Type of Publication: A1 Journal article – refereed
Field of Science: 3121 General medicine, internal medicine and other clinical medicine
Funding: Open Access funding provided by University of Oulu including Oulu University Hospital. This project has received funding from the European Social Fund (Title: “The impact of climate change on public health”, Project No. 09.3.3-LMT-K-712–19-0002) under the Grant Agreement with the Research Council of Lithuania (LMTLT).
Copyright information: © The Author(s) 2023. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated in a credit line to the data.