Multiple regression analysis of significant independent variables with zinc concentration (μmol/L) as the dependent variable
| Variable | B coefficient | P value |
| Bronchopulmonary dysplasia | – 0.43 | 0.01 |
| Birth weight z-score | 0.09 | 0.29 |
| Protein intake (g/kg/day) | – 0.10 | 0.19 |
| Length at discharge z-score | – 0.02 | 0.79 |
| Weight gain (g/day) | – 0.00 | 0.47 |