Objectives: To determine whether the association between change in bone mass density (BMD) over 4 years and risk of hip and nonvertebral fracture differs according to an individual's history of falls.
Design: Population-based cohort study.
Setting: Framingham, Massachusetts.
Participants: Individuals with two measures of BMD at the femoral neck (mean age 78.8; 310 male, 492 female).
Measurements: Cox proportional hazards models were used to estimate hazard ratios (HRs) for the association between percentage change in BMD (per sex-specific standard deviation) and risk of incident hip and nonvertebral fracture. Models were stratified based on history of falls (≥1 falls in the past year) and recurrent falls (≥2 falls) ascertained at the time of the second BMD test. Interactions were tested by including the term "fall history * change in BMD" in the models.
Results: Mean change in BMD was -0.6%/year; 27.8% of participants reported falls, and 10.8% reported recurrent falls. Seventy-six incident hip and 175 incident nonvertebral fractures occurred over a median follow-up of 9.0 years. There was no difference in the association between change in BMD and hip fracture according to history of falls (P for interaction = .57). The HR associated with change in BMD and nonvertebral fracture was 1.31 (95% confidence interval (CI) = 1.10-1.56) in participants without a history of falls and 0.95 (95% CI 0.70-1.28) in those with a fall (interaction P = .07). Results for recurrent fallers were similar.
Conclusion: The effect of BMD loss on risk of nonvertebral fracture may be greater in persons without a history of falls. It is possible that change in BMD contributes less to fracture risk when a strong risk factor for fracture, such as falls, is present.
Keywords: bone mineral density change; falls; hip fracture; nonvertebral fracture; recurrent falls.
© 2014, Copyright the Authors Journal compilation © 2014, The American Geriatrics Society.