Table 4. Associations between Initial Clinical Fracture,a Overall and by Traumatic vs Nontraumatic Mechanism, and Subsequent Clinical Fracture.
| Initial fracture mechanism | Unadjusted | Age/race adjusted | Multivariate adjustedb | |||
|---|---|---|---|---|---|---|
| HR (95% CI) | P value | HR (95% CI) | P value | HR (95% CI) | P value | |
| All fracture | 1.70 (1.57-1.84) | <.001 | 1.53 (1.42-1.66) | <.001 | 1.49 (1.38-1.61) | <.001 |
| By trauma | ||||||
| Traumatic vs no initial fracture | 1.36 (1.15-1.62) | <.001 | 1.28 (1.08-1.51) | .01 | 1.25 (1.06-1.48) | .01 |
| Nontraumatic vs no initial fracture | 1.75 (1.58-1.94) | <.001 | 1.56 (1.41-1.72) | <.001 | 1.52 (1.37-1.68) | <.001 |
| Unknown traumatic vs no initial fracture | 1.94 (1.68-2.25) | <.001 | 1.72 (1.49-2.00) | <.001 | 1.67 (1.44-1.93) | <.001 |
| Traumatic vs nontraumatic initial fracture | 0.78 (0.64-0.95) | .01 | 0.82 (0.67-1.00) | .04 | 0.82 (0.68-1.00) | .05 |
Abbreviations: HR: hazard ratio; WHI, Women’s Health Initiative.
Fracture sites included lower extremity (ankle, hip, patella, pelvis, shaft of femur, tibia/fibula, tibial plateau), upper extremity (carpal, elbow, lower end of humerus, radius/ulna, upper end of humerus, shaft of humerus, upper radius/ulna), and spine (lumbar spine, thoracic spine) fractures.
Multivariate models were adjusted for age, race, body mass index (calculated as weight in kilograms divided by height in meters squared), previous fracture, diabetes, physical function, physical activity, and frequency of falls in the past year. All models were stratified within the model to allow the baseline hazard to vary by hormone therapy use, WHI Calcium + Vitamin D intervention trial assignment, and WHI study component (WHI-CT or WHI-OS).