Table 3.
Cox regression of iron deficiency, iron deficiency anemia, and administration of IV iron, using both univariate and multivariate analyses
| Risk factor | Univariate analysis | Multivariate analysis | Multivariate excluding mediators* | ||||||
|---|---|---|---|---|---|---|---|---|---|
| HR | 95% CI | P | HR | 95% CI | P | HR | 95% CI | P | |
| Iron deficiency | |||||||||
| Age, y | 0.98 | 0.96-0.99 | .005† | 0.99 | 0.92-1.06 | .735 | 0.98‡ | 0.97-1.00 | .028† |
| Female sex | 2.85 | 1.58-5.13 | <.001† | 0.80§ | 0.01-44.3 | .914 | 2.30§ | 1.27-4.17 | .006† |
| Malabsorptive procedure | 2.46 | 1.59-3.80 | <.001† | 1.92 | 1.20-3.06 | .006† | 2.36 | 1.50-3.71 | <.001† |
| Baseline anemia | 2.94¶ | 1.88-4.60 | <.001† | 1.49¶ | 0.92-2.44 | .107 | — | — | — |
| Baseline ferritin, μg/L | 0.96¶ | 0.95-0.97 | <.001† | 0.96¶ | 0.95-0.97 | <.001† | — | — | — |
| Weight loss at 6 mo, %TBW | 1.01 | 0.99-1.03 | .480 | 0.98 | 0.96-1.00 | .066 | 0.99 | 0.97-1.01 | .492 |
| Iron deficiency anemia | |||||||||
| Age, y | 0.98 | 0.96-1.00 | .072 | 0.90 | 0.82-0.99 | .028† | 0.98 | 0.96-1.00 | .088 |
| Female sex | 1.64 | 0.70-3.81 | .252 | 0.02§ | 0.00-2.62 | .114 | 1.48§ | 0.62-3.52 | .376 |
| Malabsorptive procedure | 1.01 | 0.58-1.77 | .973 | 0.84 | 0.45-1.59 | .602 | 1.01 | 0.55-1.85 | .969 |
| Baseline anemia | 24.6¶ | 11.0-55.1 | <.001† | 19.6¶ | 7.85-48.9 | <.001† | — | — | — |
| Baseline ferritin, μg/L | 0.96¶ | 0.94-0.97 | <.001† | 0.96¶ | 0.95-0.98 | <.001† | — | — | — |
| Weight loss at 6 mo, %TBW | 0.99 | 0.95-1.02 | .399 | 0.98 | 0.94-1.02 | .335 | 0.98 | 0.95-1.02 | .278 |
| Administration of IV iron|| | |||||||||
| Age, y | 0.98 | 0.94-1.01 | .203 | — | — | — | 0.98 | 0.94-1.02 | .262 |
| Female sex | 2.45 | 0.33-18.3 | .382 | — | — | — | 2.12§ | 0.28-16.1 | .469 |
| Malabsorptive procedure | 1.62 | 0.60-4.36 | .342 | — | — | — | — | — | — |
| Baseline anemia | 1.39 | 0.47-4.14 | .550 | 1.21 | 0.40-3.63 | .736 | — | — | — |
| Baseline ferritin, μg/L | 0.99 | 0.98-1.00 | .071 | 0.99 | 0.98-1.00 | .080 | — | — | — |
| Weight loss at 6 mo, %TBW | 0.98 | 0.92-1.04 | .450 | — | — | — | — | — | — |
—, not included in the analysis.
*
This multivariate analysis excludes baseline anemia and baseline ferritin.
†
P < .05, statistically significant.
‡
The effect of age was not statistically significant with the inclusion of an interaction term for age and sex.
§
There was no significant interaction between age and sex.
¶
Time-dependent covariates were used because proportional hazards assumption was not satisfied in univariate analysis. Time measured in months.
||
The multivariate analysis included only 2 covariates to prevent overfit.