Effectiveness of oral bisphosphonates for primary prevention of osteoporotic fractures: evidence from the AIFA-BEST observational study.

Purpose: Osteoporosis is a chronic disease of the bone, whose incidence increases progressively with aging. The main consequences of osteoporosis are fragility fractures, which have considerable medical, social, and economic implications. Adequate treatment of osteoporosis must be considered as a compelling public health intervention. Bisphosphonates (BPs) represent the most significant advance in this field in the past decade, and they are widely used in the treatment of osteoporosis. However, evidence for their effectiveness is limited to secondary prevention, whereas their effect in primary prevention is uncertain and needs further investigation. Methods: Using administrative data collected in the "Biphosphonates Efficacy-Safety Tradeoff" (BEST) study, a nested case-control study was conducted by including 56,058 participants, aged 55 years who were started on oral BPs from 2003 to 2005. Cases were the 1,710 participants who were hospitalized for osteoporotic fractures until 2007. Up to 20 controls were randomly selected for each case. Conditional logistic regression model was used to estimate odds ratio of fracture associated with categories of treatment duration. Results: Compared with participants assuming BPs for less than 1 year, those who remained on therapy for at least 2 years had a 21 % (95 % confidence interval (CI) 7 to 33 %) fracture risk reduction. Conclusion: This study provides evidence that BPs, dispensed for primary prevention of osteoporotic fractures, are associated with a reduced risk of osteoporotic fractures after at least 2 years of treatment.