Plasma insulinlike growth factor 1 and binding-protein 3 and risk of myocardial infarction in women: a prospective study.

BACKGROUND The aim of this study was to prospectively evaluate relationships between plasma concentrations of insulinlike growth factor 1 (IGF1) and insulinlike growth factor binding protein 3 (IGFBP3) and subsequent myocardial infarction (MI) in women. METHODS We used case-control sampling to select study participants from women who had already been selected for inclusion in the prospective Nurses' Health Study cohort. Blood samples were collected from 32 826 women in 1989-1990. During the follow-up period from sample collection through June 1998, MI (fatal and nonfatal) was diagnosed in 245 women. Cases were matched to controls 1:2 by age, cigarette-smoking status, and month and fasting status at the time of blood collection. Conditional logistic regression was used to adjust for potential confounders (menopausal status, parental history of MI, postmenopausal hormone use, diabetes mellitus, hypertension, hypercholesterolemia, aspirin use, alcohol use, body mass index, and physical activity). RESULTS Multivariable adjusted analyses did not reveal a statistically significant linear relationship between IGF1 or IGFBP3 concentrations or their molar ratio and risk of MI. Women in the highest IGF1 quartile had a multivariable-adjusted rate ratio of 1.46 (95% CI 0.79, 2.72; P for trend = 0.46) for MI, compared with those in the lowest. The corresponding rate ratios (95% CI) for IGFBP3 and the IGF1:IGFBP3 mol/L ratio were 1.24 (0.71, 2.17) and 1.29 (0.70, 2.37), respectively. CONCLUSIONS We did not observe a monotonic relationship between IGF1 or IGFBP3 and MI among predominantly postmenopausal women. Future studies are warranted to evaluate these relationships in other demographic groups including younger women.