Myocardial infarction in young women in relation to plasma total homocysteine, folate, and a common variant in the methylenetetrahydrofolate reductase gene

Background: In a population-based study, we examined the relationship between the risk of myocardial infarction (MI) among young women and plasma total homocysteine (tHCY), folate, vitamin B₁₂, and a common cytosine (C) to thymine (T) polymorphism in the gene for 5,10-methylenetetrahydrofolate reductase (MTHFR). Methods and Results: In-person interviews and nonfasting blood samples were obtained from 79 women <45 years old diagnosed with MI and 386 demographically similar control subjects living in western Washington state between 1991 and 1995. Compared with control subjects, case patients had higher mean tHCY concentrations (13.4±5.2 versus 11.1±4.4 μmol/L, P=.0004) and lower mean folate concentrations (12.4±13.4 versus 16.1±12.2 nmol/L, P=.018). There was no difference in vitamin B₁₂ concentrations between case patients and control subjects (346.8±188.4 versus 349.7±132.4 pmol/L, P=.90). After adjusting for cardiovascular risk factors, we found that women with tHCY ≤15.6 μmol/L were at approximately twice the risk of MI as women with tHCY <10.0 μmol/L (OR, 2.3; 95% CI, 0.94 to 5.64). Women with folate ≤8.39 nmol/L had an ≃50% lower risk of MI than women with folate <5.27 nmol/L (OR, 0.54; 95% CI, 0.23 to 1.28). There was no association with vitamin B₁₂ concentration. Among control subjects, 12.7% were homozygous for the MTHFR T⁶⁷⁷ allele, and these women had higher plasma tHCY and lower plasma folate than women with other genotypes. Ten percent of case patients were homozygous for the T⁶⁷⁷ allele, and there was no association of homozygosity for T⁶⁷⁷ with MI risk (OR, 0.90; 95% CI, 0.31 to 2.29). Conclusions: These data support the hypothesis that elevated plasma tHCY and low plasma folate are risk factors for MI among young women. Although homozygosity for MTHFR T⁶⁷⁷ is related to increased plasma tHCY and low plasma folate, this genetic characteristic is not a risk factor for MI in this population.