Study Overview
Objective. To compare the risk of subsequent fractures after an initial traumatic or nontraumatic fracture in postmenopausal women.
Design. A prospective observational study utilizing data from the Women’s Health Initiative (WHI) Study, WHI Clinical Trials (WHI-CT), and WHI Bone Density Substudy to evaluate rates at which patients who suffered a traumatic fracture vs nontraumatic fracture develop a subsequent fracture.
Setting and participants. The WHI study, implemented at 40 United States clinical sites, enrolled 161 808 postmenopausal women aged 50 to 79 years at baseline between 1993 and 1998. The study cohort consisted of 75 335 patients who had self-reported fractures from September 1994 to December 1998 that were confirmed by the WHI Bone Density Substudy and WHI-CT. Of these participants, 253 (0.3%) were excluded because of a lack of follow-up information regarding incident fractures, and 8208 (10.9%) were excluded due to incomplete information on covariates, thus resulting in an analytic sample of 66 874 (88.8%) participants. Prospective fracture ascertainment with participants was conducted at least annually and the mechanism of fracture was assessed to differentiate traumatic vs nontraumatic incident fractures. Traumatic fractures were defined as fractures caused by motor vehicle collisions, falls from a height, falls downstairs, or sports injury. Nontraumatic fractures were defined as fractures caused by a trip and fall.
Main outcome measures. The primary outcome was an incident fracture at an anatomically distinct body part. Fractures were classified as upper extremity (carpal, elbow, lower or upper end of humerus, shaft of humerus, upper radius/ulna, or radius/ulna), lower extremity (ankle, hip, patella, pelvis, shaft of femur, tibia/fibula, or tibial plateau), or spine (lumbar and/or thoracic spine). Self-reported fractures were verified via medical chart review by WHI study physicians; hip fractures were confirmed by review of written reports of radiographic studies; and nonhip fractures were confirmed by review of radiography reports or clinical documentations.
Main results. In total, 66 874 women in the study (mean [SD] age) 63.1 (7.0) years without clinical fracture and 65.3 (7.2) years with clinical fracture at baseline were followed for 8.1 (1.6) years. Of these participants, 7142 (10.7%) experienced incident fracture during the study follow-up period (13.9 per 1000 person-years), and 721 (10.1%) of whom had a subsequent fracture. The adjusted hazard ratio (aHR) of subsequent fracture after an initial fracture was 1.49 (95% CI, 1.38-1.61, P < .001). Covariates adjusted were age, race, ethnicity, body mass index, treated diabetes, frequency of falls in the previous year, and physical function and activity. In women with initial traumatic fracture, the association between initial and subsequent fracture was increased (aHR, 1.25; 95% CI, 1.06-1.48, P = .01). Among women with initial nontraumatic fracture, the association between initial and subsequent fracture was also increased (aHR, 1.52; 95% CI, 1.37-1.68, P < .001). The confidence intervals for the 2 preceding associations for traumatic and nontraumatic initial fracture strata were overlapping.
Conclusion. Fractures, regardless of mechanism of injury, are similarly associated with an increased risk of subsequent fractures in postmenopausal women aged 50 years and older. Findings from this study provide evidence to support reevaluation of current clinical guidelines to include traumatic fracture as a trigger for osteoporosis screening.
Commentary
Osteoporosis is one of the most common age-associated disease that affects 1 in 4 women and 1 in 20 men over the age of 65.1 It increases the risk of fracture, and its clinical sequelae include reduced mobility, health decline, and increased all-cause mortality. The high prevalence of osteoporosis poses a clinical challenge as the global population continues to age. Pharmacological treatments such as bisphosphonates are highly effective in preventing or slowing bone mineral density (BMD) loss and reducing risk of fragility fractures (eg, nontraumatic fractures of the vertebra, hip, and femur) and are commonly used to mitigate adverse effects of degenerative bone changes secondary to osteoporosis.1