Ethel S Siris, Jingbo Yu, Katalin Bognar, Mitch DeKoven, Anshu Shrestha, John A Romley, Ankita Modi

To examine the rate of osteoporosis (OP) undertreatment and the association between gastrointestinal (GI) events and OP treatment initiation among elderly osteoporotic women with Medicare Part D drug coverage. This retrospective cohort study utilized a 20% random sample of Medicare beneficiaries. Included were women ≥66 years old with Medicare Part D drug coverage, newly diagnosed with OP in 2007-2008 (first diagnosis date as the index date), and with no prior OP treatment. GI event was defined as a diagnosis or procedure for a GI condition between OP diagnosis and treatment initiation or at the end of a 12-month follow-up, whichever occurred first. OP treatment initiation was defined as the use of any bisphosphonate (BIS) or non-BIS within 1 year postindex. Logistic regression, adjusted for patient characteristics, was used to model the association between 1) GI events and OP treatment initiation (treated versus nontreated); and 2) GI events and type of initial therapy (BIS versus non-BIS) among treated patients only. A total of 126,188 women met the inclusion criteria: 72.1% did not receive OP medication within 1 year of diagnosis and 27.9% had GI events. Patients with a GI event were 75.7% less likely to start OP treatment (odds ratio [OR]=0.243; P<0.001); among treated patients, patients with a GI event had 11.3% lower odds of starting with BIS versus non-BIS (OR=0.887; P<0.001). Among elderly women newly diagnosed with OP, only 28% initiated OP treatment. GI events were associated with a higher likelihood of not being treated and, among treated patients, a lower likelihood of being treated with BIS versus non-BIS.