© 2008 European Society of Cardiology
Hot summers and heart failure: Seasonal variations in morbidity and mortality in Australian heart failure patients (1994–2005)
a Schools of Medicine and Nursing, University of Queensland Brisbane, Australia
b Department of Clinical Pharmacology, Royal Adelaide Hospital and Faculty of Health Sciences, University of South Australia Adelaide, Australia
c Department of Clinical Pharmacology, Royal Adelaide Hospital Adelaide, Australia
d Department of Cardiology, Royal Adelaide Hospital Adelaide, Australia
e Cardiovascular Research Centre, Royal Adelaide Hospital Adelaide, Australia
f School of Medicine, University of Queensland Brisbane, Australia
g Preventative Cardiology, Baker Heart Research Institute Melbourne, Australia
* Corresponding author. Director of Clinical Pharmacology, Royal Adelaide Hospital, North Terrace, Adelaide, South Australia, 5000, Australia. Tel.: +61 8 8222 2763; fax: +61 8 8222 2907. E-mail address: sepehr.shakib{at}health.sa.gov.au
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Abstract |
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Background: There are minimal reports of seasonal variations in chronic heart failure (CHF)-related morbidity and mortality beyond the northern hemisphere.
Aims and methods: We examined potential seasonal variations with respect to morbidity and all-cause mortality over more than a decade in a cohort of 2961 patients with CHF from a tertiary referral hospital in South Australia subject to mild winters and hot summers.
Results: Seasonal variation across all event-types was observed. CHF-related morbidity peaked in winter (July) and was lowest in summer (February): 70 (95% CI: 65 to 76) vs. 33 (95% CI: 30 to 37) admissions/1000 at risk (p<0.005). All-cause admissions (113 (95% CI: 107 to 120) vs. 73 (95% CI 68 to 79) admissions/1000 at risk, p<0.001) and concurrent respiratory disease (21% vs. 12%,p<0.001) were consistently higher in winter. 2010 patients died, mortality was highest in August relative to February: 23 (95% CI: 20 to 27) vs. 12 (95% CI: 10 to 15) deaths per 1000 at risk, p<0.001. Those aged 75 years or older were most at risk of seasonal variations in morbidity and mortality.
Conclusion: Seasonal variations in CHF-related morbidity and mortality occur in the hot climate of South Australia, suggesting that relative (rather than absolute) changes in temperature drive this global phenomenon.
Key Words: Chronic heart failure • Mortality • Morbidity • Seasonality • Temperature • Hospitalisation
Received December 18, 2007; Revised February 29, 2008; Accepted March 26, 2008