Incidence and Risk of Venous Thromboembolism Among Taiwan Osteoporotic Fracture Population under Osteoporosis Pharmacological Treatments

Context: There was no clear evidence for the association between oral bisphosphonates or raloxifene and venous thromboembolism (VTE). There might also be ethnic differences in VTE risk. Objective: The purpose of this study was to compare the incidence and risk of VTEs for different classes of osteoporosis drugs in the Taiwanese osteoporotic fracture population. Design: This was a retrospective cohort study from 2003 to 2007, with up to 6 years follow-up. Setting: Enrollees were participants in Taiwan National Health Insurance. Patients: Patients older than 50 years who had vertebral or hip fractures and were new to osteoporosis therapy were recruited. Intervention: Patients were classified into the alendronate, calcitonin, or raloxifene group according to exposure after follow-up. Main Outcome Measure: The primary outcome of our study was all incident VTEs, including deep vein thrombosis and pulmonary embolism. Cox proportional hazard models were used to compare the relative VTE risk among alendronate, raloxifene, and calcitonin groups under an on-treatment scenario. Results: There were 25 443, 9642, and 31 900 patients in the alendronate, raloxifene, and calcitonin groups, and the mean age was 74.5 years (SD, 9.6). The incidence of VTE in the alendronate, raloxifene, and calcitonin groups was 11.2, 8.5, and 18.8 per 10 000 person-years. Results from Cox analyses showed that alendronate or raloxifene recipients did not have a higher risk for VTE than calcitonin recipients (adjusted hazard ratio for alendronate, 0.84; 95% confidence interval, 0.47-1.51; adjusted hazard ratio for raloxifene, 0.64; 95% confidence interval, 0.33-1.28). Conclusion: This retrospective analysis found that the incidence of VTE in Taiwanese patients with osteoporosis was low, and the risk of VTE was similar across alendronate, raloxifene, and calcitonin recipients in patients with osteoporotic fractures who were new to osteoporosis therapy.