Fig. 2From: Long-term effects of fine particulate matter exposure on the progression of arterial stiffnessThe relationship between annual average PM2.5 concentration and incidence of higher baPWV using adjusted restricted cubic spline. The reference value for each OR is the midpoint of the reference group (i.e., 76.44 μg/m3). The solid line represented estimated odds ratios and the cloud area indicated 95% CIsBack to article page