02:36am Thursday 24 October 2019

Cold weather linked to increased stroke risk in atrial fibrillation patients

“Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and it increases the risk of ischaemic stroke by four- to five-fold,” said Dr Chao. “During AF, the electrical activity of the left atrium is disordered and the contraction is ineffective which results in stasis of blood in the atrium. The blood pools and becomes sluggish and can result in the formation of blood clots. If a clot leaves the heart and travels to the brain, it can cause a stroke by blocking the flow of blood through cerebral arteries.”

 The autumn/winter season has been associated witha higher incidence and mortality rate of myocardial infarction, stroke and congestive heart failure. A greater plasma fibrinogen level and factor VII clotting activity in the winter have been reported as possible mechanisms.

 “The elevation and activation of these coagulation factors may lead to a pro-coagulant status in cool climates which may promote the formation of blood clots within the left atrium and increase the risk of stroke for AF patients,” said Dr Chao. “However until now it was unclear whether the risk of ischaemic stroke was higher in AF patients during cool seasons or on days with a lower temperature.”

 The study investigated this issue in 289 559 new-onset AF patients from the “National Health Insurance Research Database” inTaiwan during 2000 to 2011. Average daily temperatures in six regions of Taiwan were obtained from the Central Weather Bureau and average temperatures of each month and season were calculated. Taiwan is a small island and the differences in temperature between different regions were not large (Figure 1). The researchers therefore averaged the temperatures in the six regions to calculate the country average. The risk of ischaemic stroke was estimated for each month and season.

 Among the Taiwan AF cohort, 34 991 patients suffered from an ischaemic stroke during the mean follow up of three years. The risk of ischaemic stroke was higher among the months with a lower average temperature (Figure 2). In addition, the incidence of ischaemic stroke was highest in winter and lowest in summer (Figure 3). Compared to summer, the risk of ischaemic stroke increased by 10% in spring and 19% in winter. Stroke risk did not differ significantly between summer and autumn.

 “Our study shows a clear association between temperature and risk of ischaemic stroke in patients with AF,” said Dr Chao. “Risk may increase in cold weather because of the pro-coagulant status.”

 A 5 °Cdecrease in daily temperature within 14 days before the stroke occurred was associated with an increased risk of stroke with an odds ratio of 1.128 (95% confidence interval [CI] = 1.061–1.199, p

 When the average temperature was below 20 °C the risk of ischaemic stroke significantly increased compared to days with an average temperature of 30 °C. “This may be because of the increased coagulability and plasma viscosity,” said Dr Chao.

 He concluded: “In this large-scale nationwide AF registry, the risk of ischaemic stroke in AF patients was higher during cool months and seasons. The results imply that the interaction between humans and the environment may play an important role in AF-related stroke and remind us that cool climate may be an underrated issue for health which deserves more attention.”

Figure 1: Average monthly temperatures in six regions and Taiwan as a whole


 Figure 2: Distributions of mean temperature and incidence of ischaemic stroke by month




Figure 3: Incidence of ischaemic stroke by season





1Dr Chao will present the abstract ‘The relationship between cold temperature and risk of ischemic stroke in patients with atrial fibrillation’ at 09:30 during:
•    Registry I – Atrial fibrillation on Sunday 30 August at 08:30 in Hyde Park (The Hub)


Notes to editor


SOURCES OF FUNDING: The study was sponsored by Taipei Veterans General Hospital.




ESC Press Office
For background information or assistance, please contact the ESC Press Office.
For independent comment on site or interviews, please contact the ESC spokesperson coordinator: +44 7785 467 947

About the European Society of Cardiology
The European Society of Cardiology (ESC) represents more than 90 000 cardiology professionals across Europe and worldwide. Its mission is to reduce the burden of cardiovascular disease in Europe.
About ESC Congress 2015
ESC Congress is the world’s largest and most influential cardiovascular event contributing to global awareness of the latest clinical trials and breakthrough discoveries. ESC Congress 2015 takes place 29 August to 2 September at ExCel London in London, UK. Access the scientific programme. More information is available from the ESC Press Office at press@escardio.org.

To access all the scientific resources from the sessions during the congress, visit ESC Congress 365.  

This press release accompanies both a presentation and an ESC press conference at the ESC Congress 2015. Edited by the ESC from material supplied by the investigators themselves, this press release does not necessarily reflect the opinion of the European Society of Cardiology. The content of the press release has been approved by the presenter.

Share on:

MORE FROM Heart disease

Health news