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Prevalence, determinants, and misclassification of myocardial infarction in the elderly
M C de Bruyne1, A Mosterd, A W Hoes
1Department of Epidemiology and Biostatistics, Erasmus University Medical School, Rotterdam, The Netherlands.
Insights
Myocardial infarction is common in older adults, including silent heart attacks without typical symptoms. Misclassification is a significant issue in studies, highlighting the need for careful interpretation.
Area of Science:
- Cardiology
- Epidemiology
- Geriatrics
Background:
- Myocardial infarction (MI) is a leading cause of death and disability worldwide.
- Accurate identification of MI types is crucial for risk stratification and management.
- The elderly population presents unique challenges in MI diagnosis due to atypical presentations.
Purpose of the Study:
- To determine the prevalence of different myocardial infarction (MI) types in individuals aged 55 and older.
- To identify determinants associated with silent myocardial infarction.
- To assess the extent of misclassification in MI diagnosis based on available information.
Main Methods:
- Cross-sectional study involving 3,272 men and women aged 55+.
- Defined typical MI (self-reported with ECG), non-Q-wave MI (self-reported without ECG, clinically verified), and silent MI (ECG-detected, asymptomatic).
- Statistical analysis to determine prevalence, confidence intervals, and associated risk factors.
Main Results:
- Prevalence: typical MI 4.1%, non-Q-wave MI 2.8%, silent MI 3.9%.
- Silent MI was more common in women, hypertensives, smokers, and those with higher blood glucose.
- 56% of self-reported MIs without typical ECG changes were clinically verifiable.
Conclusions:
- Myocardial infarction frequently occurs in the elderly with non-traditional symptoms or ECG findings.
- All MI manifestations increase the risk of future cardiovascular events and mortality.
- Considerable misclassification can occur, necessitating careful consideration in epidemiological study design and interpretation.
Abstract:
We evaluated the prevalence, determinants, and misclassification of different types of myocardial infarction in 3,272 men and women age 55 years or older. We defined self-reported myocardial infarction with electro-cardiographic evidence as "typical myocardial infarction." We defined self-reported myocardial infarction without electrocardiographic evidence, but verified with additional clinical information, as "non-Q-wave myocardial infarction." Finally, we defined myocardial infarction detected by electrocardiogram that was not self-reported as "silent myocardial infarction," after verification of absence of symptoms. Overall, the prevalence of typical myocardial infarction was 4.1% [95% confidence interval (CI) = 3.5-4.9], of non-Q-wave myocardial infarction 2.8% (95% CI = 2.2-3.4), and of silent myocardial infarction 3.9% (95% CI = 3.2-4.5). Silent myocardial infarction was more prevalent in women, hypertensives, cigarette smokers, and those with higher post-load blood glucose. Self-reported myocardial infarction without electrocardiographic characteristics could be verified as myocardial infarction by means of additional clinical information in 56% of the cases. We conclude that myocardial infarction occurs frequently in the elderly without typical symptoms or electrocardiographic changes. As all these manifestations of myocardial infarction convey an increased risk of symptomatic heart disease or death, they require further attention. Misclassification due to limited sources of information can be considerable and should be taken into account in the design and interpretation of epidemiologic studies.