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.