Both Low and High Serum IGF-1 Levels Associate With Increased Risk of Cardiovascular Events in Elderly Men

Context: Most previous prospective studies suggest that low serum IGF-1 associates with increased risk of cardiovascular disease (CVD) events whereas other studies suggest that high serum IGF-1 associates with increased risk of CVD events. Objective: We tested the hypothesis that not only low, but also high serum IGF-1 levels associate with increased risk of CVD events in elderly men. Setting and Design: Serum IGF-1 levels were measured in 2901 elderly men (age 69-81 years) included in the Swedish cohort of the prospective, population-based Osteoporotic Fractures in Men Study (MrOS), Sweden cohort. Data for CVD events were obtained from national Swedish registers with no loss of followup. Results: During followup (median, 5.1 y) 589 participants experienced a CVD event. The association between serum IGF-1 and risk of CVD events was nonlinear, and restricted cubic spline Cox regression analysis revealed a U-shaped association between serum IGF-1 levels and CVD events (P < .01 for nonlinearity). Low as well as high serum IGF-1 (quintile 1 or 5 vs quintiles 2-4) significantly associated with increased risk for CVD events (hazard ratio [HR] = 1.25, 95% confidence interval, [CI], 1.02-1.54; and HR = 1.35, 95% CI 1.10-1.66, respectively). These associations remained after adjustment for prevalent CVD and multiple risk factors. High serum IGF-1 associated with increased risk of coronary heart disease (CHD) events but not with risk of cerebrovascular events. Conclusions: Both low and high serum IGF-1 levels are risk markers for CVD events in elderly men. The association between high serum IGF-1 and CVD events is mainly driven by CHD events