Hot summers and heart failure: seasonal variations in morbidity and mortality in Australian heart failure patients (1994-2005)

Eur J Heart Fail. 2008 Jun;10(6):540-9. doi: 10.1016/j.ejheart.2008.03.008. Epub 2008 May 20.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Cohort Studies
  • Female
  • Heart Failure / complications*
  • Heart Failure / mortality*
  • Hospitalization / statistics & numerical data
  • Hot Temperature
  • Humans
  • Incidence
  • Male
  • Middle Aged
  • Retrospective Studies
  • Risk Factors
  • Seasons*
  • Socioeconomic Factors
  • South Australia / epidemiology