Assessment of the relationship between age and the effect of risedronate treatment in women with postmenopausal osteoporosis: a pooled analysis of four studies.

OBJECTIVES: To quantify the effect of age on the incidence of osteoporosis-related fractures and of risedronate treatment on fracture risk in different age groups in women with postmenopausal osteoporosis.

DESIGN: Data from four randomized, double-blind, placebo-controlled, Phase III studies were pooled and analyzed.

PARTICIPANTS: The analysis population (N=3,229) consisted of postmenopausal women with osteoporosis as determined on the basis of prevalent vertebral fractures, low bone mineral density (BMD), or both.

INTERVENTION: Patients had received risedronate 5 mg daily or placebo for 1 to 3 years.

MEASUREMENTS: The endpoints of interest were the incidence of osteoporosis-related fractures, clinical fractures, nonvertebral fractures, and morphometric vertebral fractures. The effect of age on fracture risk and treatment benefit was examined using Cox regression models with age and treatment as explanatory variables. The 3-year fracture risk was estimated for patients in each treatment group at a given age.

RESULTS: Irrespective of treatment, fracture risks were greater in older patients (P<.001). On average, for every 1-year increase in age, a patient's risk for osteoporosis-related fracture increased 3.6% (95% confidence interval=2.3-5.0%). Irrespective of age, risedronate treatment reduced fracture risk 42%. Risedronate-treated patients had fracture risks similar to those of placebo-treated patients 10 to 20 years younger.

CONCLUSION: Patients treated with risedronate have a significantly lower fracture risk, similar to that of untreated patients 10 to 20 years younger.