Risk of Subsequent Fractures in Postmenopausal Women After Nontraumatic vs Traumatic Fractures.

Importance: The burden of fractures among postmenopausal women is high. Although nontraumatic fractures are strong risk factors for future fracture, current clinical guidelines do not address traumatic fractures.

Objective: To determine how future fracture risk varies according to whether an initial fracture is traumatic or nontraumatic.

Design, Setting, And Participants: We conducted a prospective observational study using data from the Women's Health Initiative Study (WHI) (enrollment, September 1994-December 1998; data analysis, September 2020 to March 2021), which enrolled postmenopausal women aged 50 to 79 years at baseline at 40 US clinical centers. The WHI Clinical Trials and WHI Bone Density Substudy, conducted at 3 of the clinical centers, asked participants to report the mechanism of incident fractures. Of 75 335 participants, information regarding incident fracture and covariates was available for 66 874 participants (88.8%), who comprised the analytic sample of this study. Mean (SD) follow-up was 8.1 (1.6) years.

Interventions: None.

Main Outcomes And Measures: Incident clinical fractures were self-reported at least annually and confirmed using medical records. Participants reported the mechanism of incident fracture as traumatic or nontraumatic.

Results: Among the 66 874 participants in the analytic sample (mean [SD] age, 63.1 [7.0] years and 65.3 [7.2] years among women without and with clinical fracture, respectively), 7142 participants (10.7%) experienced incident fracture during the study follow-up period. The adjusted hazard ratio (aHR) of subsequent fracture after initial fracture was 1.49 (95% CI, 1.38-1.61). Among women whose initial fracture was traumatic, the association between initial fracture and subsequent fracture was significantly increased (aHR, 1.25; 95% CI, 1.06-1.48). Among women whose initial fracture was nontraumatic, the association between initial fracture and subsequent fracture was also increased (aHR, 1.52; 95% CI, 1.37-1.68). Confidence intervals for associations between initial fracture and subsequent fracture were overlapping for traumatic and nontraumatic initial fracture strata.

Conclusions And Relevance: In this cohort study, among postmenopausal women older than 50 years, fracture was associated with a greater risk of subsequent fracture regardless of whether the fracture was traumatic or nontraumatic. These findings suggest that clinical osteoporosis assessment should include high-trauma as well as low-trauma fractures.