Table 3.
Adjusted relative hazard of fracture per sd increment in measures of femoral neck strengtha
| Models without race/ethnicity |
Models with race/ethnicity |
|||||
|---|---|---|---|---|---|---|
| RH (95% CI) for strength measure | P for strength measure | c-index (95% CI) | RH (95% CI) for strength measure | P for raceb | Increment in c-index (95% CI)c | |
| Outcome: all fractures | ||||||
| CSI | ||||||
| Model 1 | 0.70 (0.61, 0.81) | <0.001 | 0.607 (0.568, 0.646) | 0.74 (0.63, 0.86) | 0.16 | 0.012 (−0.006, 0.029) |
| Model 2 | 0.59 (0.47, 0.75) | <0.001 | 0.651 (0.615, 0.686) | 0.60 (0.48, 0.76) | 0.13 | 0.010 (−0.010, 0.031) |
| BSI | ||||||
| Model 1 | 0.70 (0.60, 0.81) | <0.001 | 0.609 (0.571, 0.648) | 0.73 (0.62, 0.86) | 0.19 | 0.011 (−0.005, 0.027) |
| Model 2 | 0.66 (0.54, 0.81) | <0.001 | 0.648 (0.614, 0.683) | 0.69 (0.56, 0.84) | 0.22 | 0.007 (−0.004, 0.017) |
| ISI | ||||||
| Model 1 | 0.72 (0.62, 0.83) | <0.001 | 0.601 (0.562, 0.639) | 0.76 (0.65, 0.88) | 0.14 | 0.013 (−0.0006, 0.027) |
| Model 2 | 0.62 (0.50, 0.78) | <0.001 | 0.646 (0.610, 0.682) | 0.63 (0.50, 0.79) | 0.11 | 0.012 (−0.004, 0.027) |
| BMD | ||||||
| Model 1 | 0.80 (0.69, 0.93) | 0.003 | 0.561 (0.523, 0.600) | 0.70 (0.60, 0.83) | <0.001 | 0.055 (0.029, 0.081) |
| Model 2 | 0.65 (0.54, 0.78) | <0.001 | 0.651 (0.616, 0.686) | 0.62 (0.51, 0.75) | 0.02 | 0.017 (−0.001, 0.036) |
| Outcome: minimum-trauma fractures | ||||||
| CSI | ||||||
| Model 1 | 0.64 (0.51, 0.80) | <0.001 | 0.644 (0.584, 0.705) | 0.67 (0.52, 0.85) | 0.19 | 0.020 (−0.005, 0.045) |
| Model 2 | 0.61 (0.43, 0.88) | 0.007 | 0.671 (0.614, 0.728) | 0.57 (0.40, 0.83) | 0.05 | 0.016 (−0.012, 0.045) |
| BSI | ||||||
| Model 1 | 0.59 (0.46, 0.75) | <0.001 | 0.664 (0.604, 0.724) | 0.62 (0.48, 0.80) | 0.28 | 0.010 (−0.005, 0.025) |
| Model 2 | 0.59 (0.43, 0.82) | 0.002 | 0.682 (0.624, 0.739) | 0.59 (0.42, 0.82) | 0.11 | 0.010 (−0.007, 0.026) |
| ISI | ||||||
| Model 1 | 0.67 (0.53, 0.84) | <0.001 | 0.638 (0.577, 0.699) | 0.70 (0.55, 0.90) | 0.15 | 0.022 (−0.006, 0.051) |
| Model 2 | 0.67 (0.47, 0.96) | 0.03 | 0.664 (0.611, 0.717) | 0.63 (0.44, 0.91) | 0.06 | 0.017 (−0.010, 0.044) |
| BMD | ||||||
| Model 1 | 0.98 (0.79, 1.22) | 0.88 | 0.561 (0.501, 0.620) | 0.81 (0.64, 1.04) | 0.01 | 0.082 (0.037, 0.126) |
| Model 2 | 0.78 (0.59, 1.04) | 0.09 | 0.656 (0.598, 0.715) | 0.68 (0.50, 0.91) | 0.02 | 0.028 (0.04, 0.053)d |
Model 1 was adjusted for study site and type of DXA scanner. Model 2 was adjusted for study site, type of DXA scanner, age, BMI, menopausal status, history of fracture since age 20 yr, smoking status, physical activity, body weight, use of medications that adversely affect bones, central nervous system active medications, alcohol consumption, supplements of vitamin D and calcium, and diabetes mellitus. RH, Relative hazard (or hazard ratio).
The sd of each strength measure was calculated in the complete study sample. In the cohort, the rate of first fracture was 12.5 per 1000 person-years; for minimum-trauma fractures, the first fracture rate was 5.3 per 1000 person-years.
P for race was computed using the likelihood ratio test for the Cox proportional hazards regression model.
Increase in area under ROC was computed using nonparametric bootstrapping.
The c-index for prediction of minimum-trauma fracture by the BMD+covariates+race/ethnicity model (0.684) was not statistically different from the c-index for any of the composite strength indices+covariates models withoutrace/ethnicity (0.671 for compression strength, 0.682 for bending strength, and 0.664 for impact strength).