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Increased winter mortality from acute myocardial infarction and stroke: the effect of age
1Preventive Cardiology and Therapeutics, Hamilton General Hospital and Division of Cardiology, McMaster University, Ontario, Canada.
Insights
Elderly individuals experience a greater increase in winter mortality from acute myocardial infarction (AMI) and stroke compared to younger populations. Understanding these seasonal patterns is key for cardiovascular disease prevention research.
Area of Science:
- Cardiovascular epidemiology
- Geriatric medicine
- Public health
Background:
- Environmental determinants of cardiovascular disease mortality, specifically acute myocardial infarction (AMI) and stroke, are not fully understood in relation to age.
- Seasonal variations in mortality may be influenced by age, but this relationship requires further investigation.
Purpose of the Study:
- To examine age-specific seasonal variations in mortality due to acute myocardial infarction (AMI) and stroke.
- To identify trends in cardiovascular mortality across different age groups throughout the year.
Main Methods:
- Analysis of approximately 300,000 deaths from the Canadian Mortality Database (1980-1982 and 1990-1992).
- Seasonal variations were assessed monthly and by season, with statistical analysis using chi-square tests and relative risk ratios (RRs).
- Mortality differences were calculated between highest and lowest frequency seasons for four age subgroups.
Main Results:
- Acute myocardial infarction (AMI) and stroke mortality peaked in January and were lowest in September, with relative risk differences of 18.6% and 19.9%, respectively.
- Seasonal variations in AMI and stroke mortality significantly increased with age, particularly for individuals over 65.
- While those under 65 showed minimal seasonal variation, mortality differences between winter and summer increased progressively in older age groups (65-74, 75-84, and >85 years).
Conclusions:
- The elderly population exhibits a more pronounced increase in winter mortality for both AMI and stroke compared to younger individuals.
- Identifying and understanding these age-dependent seasonal mortality patterns can inform new strategies for cardiovascular disease prevention.
Objectives:
We examined seasonal variations in mortality from acute myocardial infarction (AMI) and stroke by age using 300,000 deaths in the Canadian Mortality Database for the years 1980 to 1982 and 1990 to 1992.
Background:
The effect of age on environmental determinants of AMI and stroke is not well understood.
Methods:
Seasonal variations were analyzed by month and for the four seasons (winter beginning in December). A chi-square test was used to test for homogeneity at p < 0.01, and relative risk ratios (RRs) for high and low periods were determined in relation to the overall mean. For each of four age subgroups, the magnitude of the seasonal variation was reported as the difference in mortality between the highest and lowest frequency seasons.
Results:
By month, AMI deaths were highest in January (RR = 1.090) and lowest in September (RR = 0.904), a relative risk difference of 18.6%. The seasonal mortality variation in AMI deaths (winter vs. summer) increased with increasing age: 5.8% for <65, 8.3% for 65 to 74, 13.4% for 75 to 84 and 15.8% for >85 years (p < 0.005 for trend). Stroke mortality peaked in January (RR = 1.113) and had a trough in September (RR = 0.914), a relative risk difference of 19.9%. The seasonal variation in stroke mortality also increased with age. Seasonal variations were not seen in those aged <65 years, compared with 11.6% for 65 to 74, 15.2% for 75 to 84 and 19.3% for >85 years (p < 0.005 for trend).
Conclusions:
The elderly demonstrate a greater winter increase in AMI and stroke mortality than younger individuals. An understanding of these seasonal patterns may provide novel avenues for research in cardiovascular disease prevention.