Increased winter mortality from acute myocardial infarction and stroke: the effect of age
Tej Sheth, MD*,
Cyril Nair, MD ,
James Muller, MD and
Salim Yusuf, MBBS, DPhil*
* Preventive Cardiology and Therapeutics, Hamilton General Hospital and Division of Cardiology, McMaster University, Hamilton, Ontario, Canada
Statistics Canada, Ottawa, Ontario, Canada
Division of Cardiovascular Medicine, University of Kentucky, Lexington, Kentucky, USA
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Figure 1 Mortality from acute myocardial infarction (AMI) and stroke by season. Relative risks for high and low months are compared with the average of all seasons combined. There are significant winter peaks (AMI p < 0.001, stroke p < 0.001) and summer troughs (AMI p < 0.001, stroke p < 0.001) in cardiovascular disease mortality, with a large difference in AMI (9.8%) and stroke (14.3%) mortality between these two seasons.
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Figure 2 Mortality from acute myocardial infarction (AMI) and stroke by month. Relative risks for high and low months are compared with the average of all months combined. For both AMI and stroke, deaths peak in January (AMI p < 0.001, stroke p < 0.001) and then progressively decrease to a low in September (AMI p < 0.001, stroke p < 0.001). The difference in mortality from January to September is 18.6% for AMI and 19.9% for stroke.
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Figure 3 Seasonal mortality variation by age at death. At younger ages, seasonal changes have little effect on mortality from cardiovascular diseases. However, seasonal variations are more pronounced with increasing age. Among those over 85 years old, there were 15.8% more AMI and 19.3% more stroke deaths in the winter than in the summer. The slope for this trend was significant at p < 0.005 for AMI and p < 0.005 for stroke.
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