Abstract and Introduction
Abstract
Objective. This study aims to estimate the incidence of first hip or clinical vertebral fracture or major osteoporotic (hips, clinical vertebral, proximal humerus, or wrist) fracture in postmenopausal women undergoing their first bone mineral density (BMD) test before age 65 years.
Methods. We studied 4,068 postmenopausal women, aged 50 to 64 years without hip or clinical vertebral fracture or antifracture treatment at baseline, who were participating in the Women's Health Initiative BMD cohort study. BMD tests were performed between October 1993 and April 2005, with fracture follow-up through 2012. Outcomes were the time for 1% of women to sustain a hip or clinical vertebral fracture and the time for 3% of women to sustain a major osteoporotic fracture before initiating treatment, adjusting for clinical risk factors and accounting for competing risks. Women without osteoporosis and women with osteoporosis on their first BMD test were analyzed separately.
Results. During a maximum of 11.2 years of concurrent BMD and fracture follow-up, the adjusted estimated time for 1% of women to have a hip or clinical vertebral fracture was 12.8 years (95% CI, 8.0-20.4) for women aged 50 to 54 years without baseline osteoporosis, 7.6 years (95% CI, 4.8-12.1) for women aged 60 to 64 years without baseline osteoporosis, and 3.0 years (95% CI, 1.3-7.1) for all women aged 50 to 64 years with baseline osteoporosis. Results for major osteoporotic fracture were similar.
Conclusions. Because of very low rates of major osteoporotic fracture, postmenopausal women aged 50 to 64 years without osteoporosis on their first BMD test are unlikely to benefit from frequent rescreening before age 65 years.
Introduction
Although routine bone mineral density (BMD) screening is universally recommended for women aged 65 years or older, the optimal schedule for BMD screening in younger (aged 50-64 y) postmenopausal women is unknown. Four percent of US women aged 50 to 59 years and 20% of women aged 60 to 69 years were reported to have osteoporosis (very low BMD) in 1995, and the overall prevalence of osteoporosis in women aged 50 years or older decreased by 2006. Because of these low prevalence rates, identification of osteoporosis in younger postmenopausal women is challenging. Clinical practice guidelines typically encourage BMD screening in postmenopausal women younger than 65 years according to their risk factors for fracture, but there is no agreement regarding which factors to choose from lists of up to 90 predictors. Unlike most clinical screening guidelines for chronic diseases, BMD screening guidelines do not specify a standard testing interval. Younger postmenopausal women without extra risk factors for BMD loss may question whether routine (repeated) BMD testing should be performed soon after the onset of menopause or whether this test can safely be deferred. For younger postmenopausal women and their primary care providers, age-defined data are essential to shared decision-making regarding the timing of BMD tests.
For women older than 65 years, estimated time to osteoporosis is a useful metric for deciding on a BMD screening interval because of known significant fracture rates in this age range of women. In contrast, estimated time to fracture must inform the frequency of BMD screening in younger postmenopausal women because their fracture rates may be low despite transitory accelerated BMD loss immediately after the onset of menopause. In women aged 50 to 54 years, the estimated 5-year risk is 0.2% for first spine fracture and 0.0% for first hip fracture, compared with 1.5% and 0.8% for the respective risks in women aged 65 to 69 years. At the same time, a large study of postmenopausal women followed for up to 3 years after baseline peripheral (heel, forearm, or finger) BMD measures found that relative risks for fracture were similar in women aged 50 to 59 years compared with older age groups. To thoroughly examine the clinical utility of BMD screening in younger postmenopausal women, we must study those with and without osteoporosis, with adequate follow-up to estimate fracture incidence before age 65 years (when routine BMD testing is recommended).
To characterize the incidence of hip or clinical vertebral fracture in younger postmenopausal women at any baseline BMD level, we conducted competing risk analyses of 4,068 postmenopausal women aged 50 to 64 years without a history of hip or clinical vertebral fracture or osteoporosis treatment, who were followed longitudinally for up to 11 years in the Women's Health Initiative (WHI) bone density cohort. We hypothesized that younger postmenopausal women without osteoporosis (hip and lumbar spine T scores > −2.50) at baseline would be unlikely to experience a hip or clinical vertebral fracture or other major osteoporotic fractures before age 65 years.