Background: We prospectively evaluated the relationships between fasting plasma levels of vitamin B(6), as pyridoxal phosphate, and subsequent myocardial infarction risk in women.
Methods and results: Among 32 826 women who provided blood samples between 1989 and 1990 (27% of the original 1976 cohort), 239 were diagnosed with incident myocardial infarction (fatal and nonfatal) after blood collection but before July 1998. Of these women, 144 had provided a sample after fasting >10 hours. Cases were matched 1:2 by age, cigarette smoking status, and month of and fasting status at the time of blood collection with controls from the same cohort. Conditional logistic regression was used to adjust for potential confounders, including traditional coronary risk factors, anthropometric factors, dietary intake, and selected biomarkers. Median age at blood collection was 63 years. Plasma levels of pyridoxal phosphate were inversely associated with risk of myocardial infarction; the multivariable-adjusted rate ratio for the highest compared with the lowest quartiles (>70 versus <27.9 pmol/mL) was 0.22 (95% confidence interval, 0.09 to 0.55; P for trend=0.05). The association varied by age: among women who were <60 years of age at blood sampling, the rate ratio comparing the highest and lowest quartiles was 0.05 (95% confidence interval, 0.004 to 0.61), whereas among older women, the corresponding rate ratio was 0.36 (95% confidence interval, 0.13 to 1.02).
Conclusions: Fasting plasma concentration of pyridoxal phosphate was inversely associated with myocardial infarction risk, an effect that was in part independent of dietary B(6) intake. In addition to dietary vitamin B(6) intake, there are other determinants of plasma vitamin B(6) status, and these factors warrant further research.