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. 2022 Sep 9;6(10):nzac139. doi: 10.1093/cdn/nzac139

TABLE 4.

Relationships between ferritin BAZs as mediated by inflammation among PSC (6–59 months) with normal weight to overweight or obesity by survey in the BRINDA project1

CIC2 Country, survey year n PSC mediation analyses, adjusted3
Total effect Direct effect Indirect effect Mediated, % Mediated by CRP, % Mediated by AGP, %
Low Afghanistan, 2013 595 −2.8 (−11.7, 6.0) −1.9 (−10.8, 7.0) −0.9 (−2.8, 1.1) NM
Bangladesh, 2010 1179 −6.5 (−11.0, −2.3) −5.7 (−10.1, −1.6) −0.8 (−2.2, 0.5) NM
Bangladesh, 2012 368 −4.8 (−15.3, 5.5) −2.7 (−12.6, 7.1) −2.2 (−6.1, 1.7) NM
Burkina Faso, 2010 63 −10.5 (−41.9, 19.8) −10.6 (−37.8, 15.4) 0.1 (−7.5, 7.7) NM
Cambodia, 2014 599 −6.2 (−16.6, 3.8) −7.0 (−16.6, 2.0) 0.9 (−3.3, 5.0) NM
Côte d'Ivoire, 2007 435 1.4 (−7.2, 10.0) −0.6 (−8.6, 7.4) 2.0 (−2.2, 6.2) NM
Kenya, 2007 665 −7.3 (−−16.8, 1.6) −7.2 (−16.0, 1.1) −0.1 (−2.7, 2.5) NM
Kenya, 2010 551 −5.0 (−13.4, 3.2) −7.3 (−15.0, −0.2) 2.5 (−1.8, 6.7) NM
Laos, 2006 443 −5.8 (−18.2, 6.2) −4.5 (−17.2, 7.9) −1.3 (−5.0, 2.3) NM
Liberia, 2011 956 −1.6 (−6.9, 3.7) −1.7 (−7.2, 3.8) 0.1 (−1.9, 2.1) NM
Malawi, 2016 748 −3.0 (−16.4, 10.4) −1.5 (−8.5, 5.4) 1.3 (−1.5, 4.0) NM
Mongolia, 2006 239 −0.2 (−7.2, 6.7) −1.9 (−15.0, 11.2) −1.1 (−3.9, 1.7) NM
Nicaragua, 2005 946 −9.0 (−17.2, −1.7) −9.5 (−16.8, −3.1) 0.5 (−1.4, 2.4) NM
Zambia, 2009 330 −8.6 (−20.1, 2.0) −9.2 (−20.0, 0.8) 0.6 (−4.1, 5.4) NM
Low-middle Cameroon, 2009 556 12.9 (4.6, 19.7) 12.5 (4.9, 18.7) 0.3 (−1.8, 2.5) NM
Georgia, 2009 2064 0.3 (−2.5, 3.1) 0.3 (−2.5, 3.1) −0.02 (−0.1, 0.1) NM
Nigeria, 2012 303 −2.6 (−10.8, 5.5) −3.8 (−13.2, 5.5) 1.2 (−2.2, 4.7) NM
Pakistan, 2011 5824 −3.0 (−5.6, −0.5) −3.1 (−5.8, −0.6) 0.1 (−0.1, 0.3) NM
Philippines, 2011 1656 −6.2 (−12.6, −0.1) −4.3 (−10.7, 1.9) −2.0 (−3.7, −0.2) 31% 8% 23%
Vietnam, 2010 344 −11.8 (−19.4, −5.8) −11.1 (−19.1, −4.3) −0.9 (−2.5, 0.7) NM
Upper-middle Azerbaijan, 2013 987 −2.1 (−6.9, 2.7) −0.1(−4.6, 4.3) −2.0 (−4.2, 0.2) NM
Colombia, 2010 7753 −4.8 (−7.9, −1.9) −4.7 (−7.8, −1.8) −0.2 (−0.6, 0.3) NM
Mexico, 2006 1562 −3.2 (−9.0, 2.5) −3.4 (−9.3, 2.4) 0.2 (−1.3, 1.8) NM
Mexico, 2012 2454 −5.8 (−9.6, −2.3) −6.5 (−10.3, −3.2) 0.8 (−0.3, 1.8) NM
High United States, 2006 1081 −5.8 (−9.6, −2.3) −6.5 (−10.3, −3.2) 0.8 (−0.3, 1.8) NM
1

Ferritin, CRP, and AGP variables were natural-log transformed for analysis due to nonnormal distributions. Mediation estimates were exponentiated, and results are presented as percentage changes (95% CIs) in ferritin for every 1-unit change in BAZ. Ferritin concentrations were measured in serum or plasma, as reported in the survey. All estimates account for a cluster survey design (cluster, strata) with survey weights applied, except in the survey from Mongolia, which used simple random sampling. The inclusion criteria were having a BAZ or WHZ ≥ −2 SD and a negative malaria test result. AGP, alpha-1-acid glycoprotein; BAZ, BMI-for-age z-score; BRINDA, Biomarkers Reflecting Inflammation and Nutritional Determinants of Anemia; CIC, country income classification; CRP, C-reactive protein; NM, no mediation; PSC, pre-school age children; WHZ, weight-for-height z-score.

2

CIC was defined according to the World Bank definition for the year in which the survey was conducted (38).

3

Model for mediation analyses:

Inline graphic (2)

Here, all values were continuous and AGP was included as a mediator only in analyses for which it was available in the data set. Interpretation was as follows: total effect is the effect of BAZ on ferritin; direct effect is the effect of BAZ on ferritin, controlling for inflammation; and indirect effect is the effect of BAZ on ferritin as mediated by the effect of CRP or AGP. Mediation was considered present when both the total and indirect effects were significant (41). The covariates available for adjustment were age, education level (respondent or maternal education level), household socioeconomic status, access to an improved water source, access to an improved toilet, and urban or rural residence. Covariates were included in the mediation model if they were associated with the outcome variable at a P value < 0.1 in bivariate models (Supplemental Table 6). Unadjusted mediation estimates are presented in Supplemental Table 11.