Larger proportion of incident unrecognized MI in women
Sex-Based Differences in Unrecognized Myocardial Infarction
Introduction and methods
Symptoms of dyspnea, nausea and fatigue may be indicative of ischemia, and more common in women. However, these symptoms are more likely not to be mentioned by patients, or unnoted or misinterpreted by the doctor. This may lead to possible underdiagnoses of myocardial infarction (MI) [1].
Studies have investigated unrecognized MI and findings suggest that up to 64% of MI is not recognized at first presentation [2], with a larger proportion of unrecognized Mis in women [3,4]. Limitations of previous studies however are that they report prevalence of unrecognized MI and date of ascertainment (data of decades ago). More informative data on incidence of unrecognized MI is limited. This study aimed to determine sex-specific incidence rate of unrecognized MI in the Lifelines Cohort Study and describe sex-specific association with self-reported symptoms and other potential predictors.
The Lifelines Cohort Study recruited a contemporary adult population of >150.000 participants in the Netherlands to examine health and health-related behaviors [5,6] and included systematic collection of serial electrocardiographic evaluations (at baseline and 5-year follow-up visit). Participants were asked about specific symptoms in the past 7 days using questionnaires, at baseline and follow-up visits. ECGs data of 57276 women and 39927 men were available. Median follow-up was 3.8 years (3.0-4.6, 25th and 75th percentiles).
Main results
- A total of 139 (0.24%) women and 305 (0.76%) men reported to be diagnosed with MI.
- Based on ECG changes, another 59 women and 60 men were classified as having unrecognized MI. This results in a proportion of unrecognized MI in women of 30% and 16% in men (P<0.001). The difference was greatest in age categories of 40-49 and 50-59 years (43% vs. 17%, P=0.001 and 30% vs. 11%, P=0.008, respectively).
- Incidence rate of recognized MI age-standardized for the general Dutch population was 1.69 (0.84-3.19) in women and 2.67 (1.86-3.95) per 1000 person-years in men (P<0.001). For unrecognized MI, the general population adjusted incidence rate per 1000 PY follow-up was 0.23 (0.14-1.45) in women and 0.63 (0.24-1.52) in men.
- Prevalence of hypercholesterolemia was lower in individuals with unrecognized MI compared with recognized MI (24% vs. 41%, P=0.001). Compared with individuals with unrecognized MI, individuals with recognized MI more often reported chest pain or dyspnea. Dizziness and nausea were the most commonly reported symptoms in individuals with unrecognized MI. Compared with referents (without evidence of an infarction), individuals with unrecognized MI did not significantly report more symptoms.
- Hypertension, smoking status and blood glucose levels were predictors of unrecognized MI, with no difference in association between men and women.
Conclusion
The proportion of unrecognized MI was higher in women than in men (30% vs. 16%) in a contemporary adult population. This translates to an incidence rate of unrecognized MI of 0.23 in women and 0.63 in men per 1000 PYs. Notably, individuals with unrecognized MI did not report more symptoms than those without evidence of an infarction. Predictors of unrecognized MI were hypertension, smoking status and glucose levels.
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