Factor V Leiden Is Not a Risk Factor for Myocardial Infarction Among Young Women

Several large-scale studies indicate that factor V Leiden (FVL) is not associated with an increased risk of acute myocardial infarction (MI) in middle-aged or elderly populations.1-7 However, Rosendaal et al8 have hypothesized that FVL might increase the risk of myocardial infarction among women less than 45 years of age, particularly in the subgroup of smokers. Specifically, in a study of 84 women with premature myocardial infarction, 8 were found to carry FVL (binomial 95% confidence interval [CI], 4.2% to 17.9%). In the subgroup of smokers who carried FVL, 7 of 62 were found to be carriers of FVL (binomial 95% CI, 4.6% to 21.9%). Based on these data and on an observed control prevalence of 4.1%, the investigators reported a 32-fold increased risk of MI among the subgroup of young female smokers who carried FVL as compared with nonsmokers free of the mutation. To directly evaluate this hypothesis, we used polymerase chain reaction techniques to determine FVL status among 36 women in the Boston area who suffered a myocardial infarction before 45 years of age and compared the prevalence of this mutation with an age-, ethnicity-, and smoking-matched group of community-based controls, as well as with the mutation rate previously reported in a large-scale populationbased study of FVL in the United States.9 The average age of case subjects at the time of the MI was 39 years; 52% were smokers. As expected, case subjects were heavier, more likely to have a family history of premature atherothrombosis, and more likely to be treated for hypertension and hyperlipidemia, as compared with community-based controls. We found no evidence in these data that FVL increased the risk of MI (Table 1). Specifically, of the 36 case subjects, 1 (2.7%) was heterozygous for FVL, as compared with 3 (8.3%) of the controls (P 5 .3). Similarly, the prevalence of the mutation in the case group (2.7%) was not statistically different from the 4.8% prevalence rate previously reported in a large-scale population-based study of American women free of any history of coronary disease (P 5 .6). Moreover, in the subgroup of smokers, only 1 of 19 (5.2%) case subjects with MI was found to carry FVL. Thus, these data do not support the hypothesis that FVL is an important risk factor for MI among young women, regardless of smoking status. ACKNOWLEDGMENT