A pilot survey of selenium status and its geospatial variation among children and women in three rural districts of Zimbabwe

Abstract

IntroductionSelenium (Se) deficiency is increasingly recognized as a public health problem in sub-Saharan Africa.MethodsThe current cross-sectional study assessed the prevalence and geospatial patterns of Se deficiency among children aged 6–59 months (n = 741) and women of 15–49 years old (n = 831) selected by simple random sampling in rural Zimbabwe (Murewa, Shamva, and Mutasa districts). Venous blood samples were collected and stored according to World Health Organization guidelines. Plasma Se concentration was determined by inductively coupled plasma-mass spectrometry.ResultsMedian, Q1, and Q3 plasma Se concentrations were 61.2, 48.7, and 73.3 μg/L for women and 40.5, 31.3, and 49.5 μg/L for children, respectively. Low plasma Se concentrations (9.41 μg/L in children and 10.20 μg/L in women) indicative of severe Se deficiency risk was observed. Overall, 94.6% of children and 69.8% of women had sub-optimal Se status defined by plasma Se concentrations of <64.8 μg/L and <70 μg/L, respectively.DiscussionHigh and widespread Se deficiency among women and children in the three districts is of public health concern and might be prevalent in other rural districts in Zimbabwe. Geostatistical analysis by conditional kriging showed a high risk of Se deficiency and that the Se status in women and children in Murewa, Shamva, and Mutasa districts was driven by short-range variations of up to ⁓12 km. Selenium status was homogenous within each district. However, there was substantial inter-district variation, indicative of marked spatial patterns if the sampling area is scaled up. A nationwide survey that explores the extent and spatial distribution of Se deficiency is warranted.

Urine Se concentration poorly predicts plasma Se concentration at sub-district scales in Zimbabwe, limiting its value as a biomarker of population Se status

“…The overall median (Q1, Q3) Se concentrations were 61.2 μg/L (48.7, 73.3) and 40.5 μg/L (31.3, 49.5) for children and women, respectively. Notable evidence of severe Se deficiency risk was observed in the sample population, with children recording plasma Se concentrations as low as 9.41 μg/L and 10.20 μg/L being the minimum in WRA ( 40 ). The urine and plasma samples were collected from individuals on the same day, allowing for comparison of urine and plasma at individual, household, EA, and district levels.…”

“…The current study assesses the usefulness of casual urine Se concentration as an alternative biomarker to plasma Se concentration, which has previously been reported ( 40 ), for the population-level Se status. The plasma Se study found that Se deficiency is widespread among women and children in all three rural districts.…”

“…Study design and methods are described in detail elsewhere ( 40 , 43 ). The sampling design was nested at the level of the National Demographic Health Survey (DHS) sampling approach ( 44 ).…”

“… Sampling locations of eligible households ( n = 900) from which study participants were recruited in Shamva, Murehwa, and Mutasa districts, rural Zimbabwe [adapted from Mutonhodza et al ( 40 )]. …”

“…In Zimbabwe, food systems are localized, with a large proportion of diets coming from their own production or locally traded foods ( 38 , 39 ), meaning that dietary exposures are closely related to the concentrations of plant-available Se in surrounding agricultural soils, and in these contexts, spatial variation in Se exposures at different scales is expected ( 9 ). The current study tested if casual urine is a practicable biomarker for measuring the Se status of children and WRA in a population where Se status is under strong geospatial control ( 40 ) by comparing casual urine Se status with plasma Se status. The study also examined the usefulness of urine Se concentration in predicting plasma Se concentration at different population scales: between district, enumeration areas (EAs) within district, and households (HHs) within EAs.…”