Risk of new vertebral fracture in the year following a fracture.

CONTEXT: Vertebral fractures significantly increase lifetime risk of future fractures, but risk of further vertebral fractures in the period immediately following a vertebral fracture has not been evaluated. OBJECTIVE: To determine the incidence of further vertebral fracture in the year following a vertebral fracture. DESIGN AND SETTING: Analysis of data from 4 large 3-year osteoporosis treatment trials conducted at 373 study centers in North America, Europe, Australia, and New Zealand from November 1993 to April 1998. SUBJECTS: Postmenopausal women who had been randomized to a placebo group and for whom vertebral fracture status was known at entry (n = 2725). MAIN OUTCOME MEASURE: Occurrence of radiographically identified vertebral fracture during the year following an incident vertebral fracture. RESULTS: Subjects were a mean age of 74 years and had a mean of 28 years since menopause. The cumulative incidence of new vertebral fractures in the first year was 6.6%. Presence of 1 or more vertebral fractures at baseline increased risk of sustaining a vertebral fracture by 5-fold during the initial year of the study compared with the incidence in subjects without prevalent vertebral fractures at baseline (relative risk [RR], 5.1; 95% confidence interval [CI], 3.1-8.4; P<.001). Among the 381 participants who developed an incident vertebral fracture, the incidence of a new vertebral fracture in the subsequent year was 19.2% (95% CI, 13.6%-24.8%). This risk was also increased in the presence of prevalent vertebral fractures (RR, 9.3; 95% CI, 1.2-71.6; P =.03). CONCLUSION: Our data indicate that women who develop a vertebral fracture are at substantial risk for additional fracture within the next year.