Table 6.
Multivariate regression analyses†,‡ assessing determinants of serum ferritin in non-pregnant non-lactating women (NPNLW; 15–49 years old), school age children (SAC; 6–14 years old) and pre-school age children (PSAC; 6–59 months old), Bangladesh, 2011–2012
| NPNLW | SAC | PSAC | |||||||
|---|---|---|---|---|---|---|---|---|---|
| t | P | Standardized β | t | P | Standardized β | t | P | Standardized β | |
| Covariates | |||||||||
| Hb | 0·08 | 0·93 | 0·005 | −0·06 | 0·95 | −0·004 | 2·05 | 0·04 | 0·15 |
| Household expenditure§ | −1·06 | 0·29 | −0·09 | 1·63 | 0·10 | 0·13 | – | – | – |
| Woman’s institutional education (ref.: no institutional education) | 0·42 | 0·67 | 0·03 | – | – | – | – | – | – |
| Agricultural profession (ref.: non-agricultural) | – | – | – | −2·18 | 0·03 | −0·19 | 1·13 | 0·25 | 0·08 |
| Age | – | – | – | – | – | – | 4·42 | <0·001 | 0·30 |
| Female sex (ref.: male) | – | – | – | 1·47 | 0·14 | 0·10 | −1·9 | 0·06 | −0·13 |
| No diarrhoea (ref.: diarrhoea) | – | – | – | 0·53 | 0·60 | 0·04 | – | – | – |
| Wealth index (ref.: poorest) | |||||||||
| Poorer | 2·21 | 0·03 | 0·18 | – | – | – | 0·30 | 0·76 | 0·03 |
| Middle | 0·75 | 0·45 | 0·06 | – | – | – | −1·03 | 0·30 | −0·09 |
| Richer | −0·69 | 0·49 | −0·05 | – | – | – | −0·77 | 0·44 | −0·06 |
| Richest | 2·27 | 0·02 | 0·29 | – | – | – | −1·87 | 0·06 | −0·17 |
| Groundwater Fe (ref.: PLGWI area) | |||||||||
| PHGWI area | 2·10 | 0·03 | 0·19 | 2·56 | 0·01 | 0·22 | 2·12 | 0·03 | 0·20 |
| 7 d total Fe intake | −0·03 | 0·97 | −0·001 | – | – | – | – | – | – |
| No knowledge of health benefits of eating Fe-rich foods (ref.: knowledgeable) | – | – | – | −0·60 | 0·55 | 0·04 | – | – | – |
| Knowledge about foods that are rich in Fe (ref.: no knowledge) | −1·62 | 0·10 | −0·11 | −1·78 | 0·08 | −0·16 | – | – | – |
| Area of residence (ref.: rural) | |||||||||
| Urban | 0·74 | 0·45 | 0·05 | −2·52 | 0·01 | −0·19 | 0·61 | 0·54 | 0·04 |
| Slum | 0·62 | 0·53 | 0·04 | 0·03 | 0·97 | 0·02 | −0·19 | 0·85 | −0·01 |
| Serum retinol | −0·07 | 0·94 | −0·004 | 1·48 | 0·14 | 0·10 | – | – | – |
| Parity | −2·76 | 0·006 | −0·18 | – | – | – | – | – | – |
| Serum Zn | −0·35 | 0·72 | −0·03 | – | – | – | – | – | – |
| Household food insecurity (ref.: food secure) | |||||||||
| Mild food insecurity | 2·26 | 0·02 | 0·20 | −0·21 | 0·83 | −0·01 | 1·71 | 0·09 | 0·16 |
| Moderate food insecurity | 3·38 | 0·001 | 0·58 | 2·06 | 0·04 | 0·20 | 1·36 | 0·17 | 0·27 |
| Severe food insecurity | 2·85 | 0·005 | 0·60 | −0·72 | 0·47 | −0·08 | 1·61 | 0·10 | 0·28 |
| Serum vitamin B12 || | 1·83 | 0·07 | 0·12 | – | – | – | – | – | – |
| Serum folate|| | 2·3 | 0·02 | 0·15 | – | – | – | – | – | – |
| Possession of refrigerator (ref.: non-possession) | 2·91 | 0·004 | 0·27 | – | – | – | – | – | – |
| Non-possession of electricity (ref.: possession) | – | – | – | 2·12 | 0·03 | 0·19 | – | – | – |
| Interaction | |||||||||
| (Groundwater Fe × household food insecurity | −2·33 | 0·02 | −0·52 | −1·54 | 0·12 | −0·35 | |||
Ref., reference category; PLGWI, predominantly low groundwater Fe; PHGWI, predominantly high groundwater Fe.
The empty fields in the table imply either not applicable or not entered in the multivariate model as the univariate or bivariate analyses were non-significant (P>0·05).
The covariates, which were assumed to have interaction, were entered in regression as an interaction term along with the interacting predictors. Interactions of (groundwater Fe×household food insecurity) in NPNLW (P=0·009) and PSAC (P=0·05) were entered in the final multivariate regression; however, in the final multivariate model significant interaction was reported for the NPNLW (P=0·02) while in PSAC the interaction was non-significant (P=0·12). In SAC, (groundwater Fe × household food insecurity) was non-significant in the initial regression and not included in the final model. In SAC, the term (groundwater Fe×stratum) had a significant interaction (P=0·01) in the initial regression; however it was not included in the final model as its inclusion would result in significant multicollinearity.
Log-transformed for SAC.
Log-transformed for NPNLW.