Table 4.
Robust multiple linear regression to identify factors associated with vitamin A concentrations.
| Vitamin A (serum) | Dependent variables | Standardized coefficients | P value |
|---|---|---|---|
| Age (years) | 0.068 | 0.620 | |
| Gender (male) | −0.161 | 0.086 | |
| Smoking status (yes) | 0.197 | 0.042 | |
| IL-6 × CRP × TNF-α (pg/mL) | 0.112 | 0.247 | |
| Presence of COPD (yes) | −0.480 | 0.001 |
R 2 = 0.26. For robust multiple linear regressions, clinically relevant variables were selected. The included categorical variables were gender (female = 0, male = 1), smoking status (absence = 0, presence = 1), presence of COPD (absence = 0, presence = 1), the interaction of IL-6 × CRP × TNF-α (was considered by multiplying the variables to construct one variable), and age as a continuous variable.