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Spatial analysis of urine zinc (Zn) concentration for women of reproductive age and school age children in Malawi.

ABSTRACT: Zinc (Zn) is an essential micronutrient, and Zn deficiency remains a major global public health challenge. Recognised biomarkers of population Zn status include blood plasma or serum Zn concentration and proxy data such as dietary Zn intake and prevalence of stunting. Urine Zn concentration is rarely used to assess population Zn status. This study assessed the value of urine Zn concentration as a biomarker of population Zn status using a nationally representative sample of non-pregnant women of reproductive age (WRA) and school-aged children (SAC) in Malawi. Spot (casual) urine samples were collected from 741 WRA and 665 SAC. Urine Zn concentration was measured by inductively coupled plasma mass spectrometry with specific gravity adjustment for hydration status. Data were analysed using a linear mixed model with a spatially correlated random effect for between-cluster variation. The effect of time of sample collection (morning or afternoon), and gender (for SAC), on urine Zn concentration were examined. There was spatial dependence in urine Zn concentration between clusters among SAC but not WRA, which indicates that food system or environmental factors can influence urine Zn concentration. Mapping urine Zn concentration could potentially identify areas where the prevalence of Zn deficiency is greater and thus where further sampling or interventions might be targeted. There was no evidence for differences in urine Zn concentration between gender (P?=?0.69) or time of sample collection (P?=?0.85) in SAC. Urine Zn concentration was greater in afternoon samples for WRA (P?=?0.003). Relationships between urine Zn concentration, serum Zn concentration, dietary Zn intake, and potential food systems covariates warrant further study.

SUBMITTER: Phiri FP

PROVIDER: S-EPMC7847879 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Spatial analysis of urine zinc (Zn) concentration for women of reproductive age and school age children in Malawi.

Phiri Felix P FP Ander E Louise EL Lark R Murray RM Joy Edward J M EJM Kalimbira Alexander A AA Suchdev Parminder S PS Gondwe Jellita J Hamilton Elliott M EM Watts Michael J MJ Broadley Martin R MR

Environmental geochemistry and health 20200830 1

Zinc (Zn) is an essential micronutrient, and Zn deficiency remains a major global public health challenge. Recognised biomarkers of population Zn status include blood plasma or serum Zn concentration and proxy data such as dietary Zn intake and prevalence of stunting. Urine Zn concentration is rarely used to assess population Zn status. This study assessed the value of urine Zn concentration as a biomarker of population Zn status using a nationally representative sample of non-pregnant women of ...[more]

PMID: 32862269

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Project description:BackgroundIn low-resource settings, urbanization may contribute to the individual-level double burden of malnutrition (DBM), whereby under- and overnutrition co-occur within the same individuals.ObjectiveWe described DBM prevalence among Malawian women by urban-rural residence, examined whether urban residence was associated with DBM, and assessed whether DBM prevalence was greater than the prevalence expected by chance given population levels of under- and overnutrition, which would suggest DBM is a distinct phenomenon associated with specific factors.MethodsWe analyzed nationally representative data of 723 nonpregnant women aged 15-49 y from the 2015-2016 Malawi Micronutrient Survey. DBM was defined as co-occurring overweight or obesity (OWOB) and ≥1 micronutrient deficiency or anemia. We used Poisson regression models to examine the association between urban residence and DBM and its components. The Rao-Scott modified chi-square test compared the observed and expected DBM prevalence.ResultsNationally, 10.8% (95% CI: 7.0, 14.5) of women had co-occurring OWOB and any micronutrient deficiency and 3.4% (95% CI: 1.3, 5.5) had co-occurring OWOB and anemia. The prevalence of co-occurring OWOB and any micronutrient deficiency was 2 times higher among urban women than rural women [urban 32.6 (24.1, 41.2) compared with rural 8.6 (5.2, 11.9), adjusted prevalence ratio: 2.0 (1.1, 3.5)]. Co-occurring OWOB and anemia prevalence did not significantly differ by residence [urban 6.9 (0.6, 13.2) compared with rural 3.0 (0.8, 5.3)]. There were no statistically significant differences in observed and expected prevalence estimates of DBM.ConclusionsThis analysis shows that co-occurring OWOB and any micronutrient deficiency was higher among women in urban Malawi compared with rural areas. However, our finding that co-occurring OWOB and any micronutrient deficiency or anemia may be due to chance suggests that there may not be common causes driving DBM in Malawian women. Thus, there may not be a need to design and target interventions specifically for women with DBM.

Project description:Dietary zinc (Zn) deficiency is widespread globally, and in particular among people in sub-Saharan Africa (SSA). In Malawi, dietary sources of Zn are dominated by maize and spatially dependent variation in grain Zn concentration, which will affect dietary Zn intake, has been reported at distances of up to ~ 100 km. The aim of this study was to identify potential soil properties and environmental covariates which might explain this longer-range spatial variation in maize grain Zn concentration. Data for maize grain Zn concentrations, soil properties, and environmental covariates were obtained from a spatially representative survey in Malawi (n = 1600 locations). Labile and non-labile soil Zn forms were determined using isotopic dilution methods, alongside conventional agronomic soil analyses. Soil properties and environmental covariates as potential predictors of the concentration of Zn in maize grain were tested using a priori expert rankings and false discovery rate (FDR) controls within the linear mixed model (LMM) framework that informed the original survey design. Mean and median grain Zn concentrations were 21.8 and 21.5 mg kg-1, respectively (standard deviation 4.5; range 10.0-48.1). A LMM for grain Zn concentration was constructed for which the independent variables: soil pH(water), isotopically exchangeable Zn (ZnE), and diethylenetriaminepentaacetic acid (DTPA) extractable Zn (ZnDTPA) had predictive value (p < 0.01 in all cases, with FDR controlled at < 0.05). Downscaled mean annual temperature also explained a proportion of the spatial variation in grain Zn concentration. Evidence for spatially dependent variation in maize grain Zn concentrations in Malawi is robust within the LMM framework used in this study, at distances of up to ~ 100 km. Spatial predictions from this LMM provide a basis for further investigation of variations in the contribution of staple foods to Zn nutrition, and where interventions to increase dietary Zn intake (e.g. biofortification) might be most effective. Other soil and landscape factors influencing spatially dependent variation in maize grain Zn concentration, along with factors operating over shorter distances such as choice of crop variety and agronomic practices, require further exploration beyond the scope of the design of this survey.

Dataset Information

Spatial analysis of urine zinc (Zn) concentration for women of reproductive age and school age children in Malawi.

Publications

Spatial analysis of urine zinc (Zn) concentration for women of reproductive age and school age children in Malawi.

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