Fig. 1

Spline analysis of the association between serum levels of FGF-21 and incident type 2 diabetes in women (a) and men (b). The Solid line represents point estimates of relative risk for the association between FGF-21 and incident type 2 diabetes, and the dotted lines represent the upper and lower bound of 95% CI. Study participants with the lowest and highest 1% of FGF-21 were excluded to minimize the potential impact of outliers. Cubic spline analysis was used to examine the association between FGF-21 concentrations and risk of developing type 2 diabetes using the most fully-adjusted models from reported studies. P for nonlinearity =0.09 in women (a) P for nonlinearity =0.86 in men (b) in the cubic spline regression model