Figure 2: Relationship between waist circumference (WC) and erectile dysfunction (ED) severity as expressed as tertiles of the SIEDY validated index of ED severity (a)42 or short version of the International Index of Erectile function (b; IIEF-5).47 (c) age, total testosterone (TT) and smoking habit adjusted contribution of organic, marital or psychological factors as derived from SIEDY scales43,45,46 in obesity-associated ED. Data are reported as a function of age tertiles (black, gray and open diamonds for I: 17-45, II: 46-59 and III: 60-88 years; age tertiles, respectively). (d) relationship between WC and prostaglandin E1 (PGE1)-stimulated (dynamic) peak systolic velocity (D-PSV). Data (unpublished) are derived from a nonselected series of men (mean age = 51.3 ± 13.3 years) attending our Sexual Medicine and Andrology Clinic for sexual dysfunction between 2000 and 2013. The age-TT-smoking habit correlation coefficients for the indicated observations are also reported in a , b and d . Note that WC was considered as a continuous variable in all the analyses.