Independent association of osteopenia/osteoporosis (OP) with atherosclerotic plaque formation in patients with primary Sjogren's syndrome (SS). (A) Association of osteopenia/OP with plaque formation in SS (odds ratio (OR) 4.0, 95% CI 1.3, 12.2, P = 0.01). This association remained significant when potential confounders for both clinical entities, such as age, total steroid dose and smoking, were taken in consideration. (B) Patients with primary SS characterized by low Dickkopf-related protein 1 (DKK1) levels had reduced bone mass levels compared to those with high DKK1 levels (0.7 ± 0.1 versus 0.9 ± 0.1 mg/cm2, P = 0.002). (C) Similarly, patients with primary SS with low DKK1 levels had increased rates of plaque formation (81.8% versus 53.3%). The sum of the mean + 2 SD of healthy controls (HC) (2403.6 pg/ml) was considered as the cut off value for low and high DKK1 levels.