The seasonality in heart failure deaths and total cardiovascular deaths

Objectives: To examine the seasonal pattern in heart failure (HF) and cardiovascular disease (CVD) by climate and cause of death in Australia. Methods: A retrospective analysis of a national database of deaths in the eight Australian State and Territory capitals between January 1997 and November 2004. We examined the seasonal pattern in HF and CVD deaths, we identified variations in the pattern by: sex, age, time, climate and cause of death (for total CVD using seven groups determined by ICD-10 code). Results: Deaths in all seven groups of CVD significantly increased in winter. The largest increase in mortality rates was 23.5% observed for HF. The magnitude of this increase varied greatly between cities, with the lowest winter mortality rates in the coldest (Hobart) and warmest (Darwin) cities. The pattern in CVD deaths showed a clearer correlation with climate than HF deaths. Conclusion and implications: Winters in Australia are mild but winter increases in HF and CVD are a significant problem. Increased blood pressure and lack of vitamin D in winter are the most likely causes of the increase. Reducing exposure to cold, particularly in the elderly, should reduce the number of winter CVD deaths in Australia.