Longitudinal progression of fracture prevalence through a population of postmenopausal women with osteoporosis

Aim: To determine the longitudinal progression of fractures through a population of osteoporotic women with no existing vertebral fractures. Methods: The probability of having one or more vertebral fractures in the next year given a current status of 0-13 existing vertebral fractures was estimated using data from control patients of an osteoporosis clinical trial program. Fracture probabilities were used to form a transition matrix that models the change in fracture state from one year to the next. A Markov model was used to show the distribution of fracture prevalence over time for a population of women with osteoporosis but, initially, with no existing vertebral fractures. Results: An osteoporotic woman without existing vertebral fractures has a 7.7% chance (95% CI, 5.8% to 9.9%) of having a vertebral fracture within 1 year. After 5 years, 33% (95% CI, 25% to 41%) will have developed vertebral fractures, of which 11% (95% CI, 8% to 16%) will have greater than or equal to2 fractures. After 10 years, 55% (95% CI, 44% to 65%) will have developed vertebral fractures, of which 29% (95% CI, 22% 37%) will have greater than or equal to2 fractures. Each 1% absolute reduction in the annual first-fracture risk corresponds to an approximate 4% reduction in the 5-year fracture incidence. Therefore, reducing the risk of first fracture from 8% to 2% reduces the 5-year fracture incidence from similar to34% to similar to10%. Conclusions: Fracture prevalence rapidly increases over time in a population of osteoporotic women despite treatment with calcium and vitamin D supplements. Identifying and treating patients at risk of fracture, but who have not yet sustained a fracture, will substantially reduce the long-term burden of osteoporosis.