Traditional risk factors may not explain increased incidence of myocardial infarction in MS.

OBJECTIVE

To compare the risk of incident acute myocardial infarction (AMI) in the multiple sclerosis (MS) population and a matched population without MS, controlling for traditional vascular risk factors.

METHODS

We conducted a retrospective matched cohort study using population-based administrative (health claims) data in 2 Canadian provinces, British Columbia and Manitoba. We identified incident MS cases using a validated case definition. For each case, we identified up to 5 controls without MS matched on age, sex, and region. We compared the incidence of AMI between cohorts using incidence rate ratios (IRR). We used Cox proportional hazards regression to compare the hazard of AMI between cohorts adjusting for sociodemographic factors, diabetes, hypertension, and hyperlipidemia. We pooled the provincial findings using meta-analysis.

RESULTS

We identified 14,565 persons with MS and 72,825 matched controls. The crude incidence of AMI per 100,000 population was 146.2 (95% confidence interval [CI] 129.0-163.5) in the MS population and 128.8 (95% CI 121.8-135.8) in the matched population. After age standardization, the incidence of AMI was higher in the MS population than in the matched population (IRR 1.18; 95% CI 1.03-1.36). After adjustment, the hazard of AMI was 60% higher in the MS population than in the matched population (hazard ratio 1.63; 95% CI 1.43-1.87).

CONCLUSION

The risk of AMI is elevated in MS, and this risk may not be accounted for by traditional vascular risk factors.