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Open Access Highly Accessed Research article

Association between winter season and risk of death from cardiovascular diseases: a study in more than half a million inpatients in Beijing, China

Beibei Xu1, Hui Liu1, Naifang Su1, Guilan Kong1, Xiaoyuan Bao1, Jiong Li2, Jing Wang1, Yi Li1, Xiemin Ma3, Jun Zhang14, Guo-Pei Yu15* and Lueping Zhao16*

Author Affiliations

1 Medical Informatics Center, Peking University, 38 Xueyuan Rd, Haidian District, 100191, Beijing, China

2 Section for Epidemiology, Department of Public health, Aarhus University, Aarhus, Denmark

3 Department of Hospital Management, School of Public Health, Peking University, Beijing, China

4 Department of Hospital Administration of Peking University Health Science Center, Peking University, Beijing, China

5 New York Medicine College, Valhalla, NY, USA

6 Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA

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BMC Cardiovascular Disorders 2013, 13:93  doi:10.1186/1471-2261-13-93

Published: 30 October 2013

Abstract

Background

Seasonal associations of cardiovascular mortality have been noted in most populations of European origin years ago, but are not well evaluated in Asian populations recently.

Methods

Utilizing the electronic Hospitalization Summary Reports (HSRs) from 32 top-ranked hospitals in Beijing, China, we evaluated the association between winter season and the risk of cardiovascular death among hospitalized individuals. General additive models and logistic regression models were adjusted for confounding factors.

Results

Older patients who were admitted to the hospital in the winter months (January, February, November and December) had a death risk that was increased by approximately 30% to 50% (P < 0.01) over those who were admitted in May. However, younger patients did not seem to experience the same seasonal variations in death risk. The excess winter deaths among older patients were associated with ischemic heart disease (RR = 1.22; 95% CI 1.13 to 1.31), pulmonary heart disease (RR = 1.42; 95% CI 1.10 to 1.83), cardiac arrhythmias (RR = 1.67; 95% CI 1.36 to 2.05), heart failure (RR = 1.30; 95% CI 1.09 to 1.54), ischemic stroke (RR = 1.30; 95% CI 1.17 to 1.43), and other cerebrovascular diseases (RR = 1.78; 95% CI 1.40 to 2.25). The risks of mortality were higher in winter months than in the month of May, regardless of the presence or absence of respiratory disease.

Conclusions

Winter season was associated with a substantially increased risk of cardiovascular death among older Chinese cardiovascular inpatients.

Keywords:
Cardiovascular disease; Winter; Seasonality; Older adults; Mortality; Asian population