OBJECTIVE: There are many effective osteoporosis (OP) medications with a variety of dosing intervals and delivery options, but even when diagnosed, OP is often undertreated. We sought to determine the bone density consequences of the decision to initiate and comply with therapy for OP.

METHODS: We identified 243 women who received a dual x-ray absorptiometry (DXA) evaluation and fulfilled the World Health Organization criteria for OP. One year later, the patients were asked to return for a followup DXA. Administrative electronic health records were used to identify prescription drug use.

RESULTS: A total of 142 women (58%) initiated pharmacologic therapy for OP during the year after the initial DXA; 144 returned for a followup DXA after 1 year. For those women with >/=66% of days receiving therapy, the mean annual change in spine bone mineral density (BMD) was 4.5% compared with 2.0% for those with <66% of days receiving therapy and 0.8% for those not receiving OP therapy (P < 0.001). For those women with >/=66% of days receiving therapy, the mean change in hip BMD was 2.3% compared with 0.3% for those with <66% of days receiving therapy and -0.8% for those not receiving OP therapy (P < 0.001).

CONCLUSION: We found significant bone density consequences of the decision to initiate and comply with therapy in the first year after diagnosis of OP. Improvement in both initiation rates of treatment as well as compliance are needed in order to reduce the frequency of osteoporotic fractures.