Challenges for Estimating the Global Prevalence of Micronutrient Deficiencies and Related Disease Burden: A Case Study of the Global Burden of Disease Study

Abstract

Information on the prevalence of micronutrient deficiencies is needed to determine related disease burden; underpin evidence-based advocacy; and design, deliver, and monitor safe, effective interventions. Assessing the global prevalence of deficiency requires a valid micronutrient status marker with an appropriate cutoff to define deficiency and relevant data from representative surveys across multiple locations and years. The Global Burden of Disease Study includes prevalence estimates for iodine, iron, zinc, and vitamin A deficiencies, for which recommended biomarkers and appropriate deficiency cutoffs exist. Because representative survey data are lacking, only retinol concentration is used to model vitamin A deficiency, and proxy indicators are used for the other micronutrients (goiter for iodine, hemoglobin for iron and dietary food adequacy for zinc). Because of data limitations, complex statistical modeling is required to produce current estimates, relying on assumptions and proxies that likely understate the extent of micronutrient deficiencies and the consequent global health burden. Brief lay summary In this review, steps needed to estimate micronutrient deficiency prevalence and related disease burdens are described; challenges are outlined using the Global Burden of Disease Study as a case study.

Basis for changes in the disease burden estimates related to vitamin A and zinc deficiencies in the 2017 and 2019 Global Burden of Disease Studies

“…Thus, additional effort is needed to validate these results. Moreover, the use of proxy indicators may obscure the well-recognised issue of data scarcity concerning population micronutrient status (40) , and thus discourage investments in much needed micronutrient status biomarker information collected from representative samples of various population groups (10) .…”

“…diarrhoea attributable to vitamin A deficiency) (9) . The modelling strategies for these two approaches differ, but in both approaches the first step is to estimate the prevalence of the micronutrient deficiency of interest (10) . In the risk factor approach, which is used to estimate the attributable deaths and disability-adjusted life-years, the disease burden and mortality estimates are based on findings of meta-analyses of randomised controlled trials of the effects of providing additional amounts of the MN and are modelled specifically for the population attributable fraction of a target population group that is deemed to be deficient.…”

Accelerating action to reduce anemia: Review of causes and risk factors and related data needs

“…16,[68][69][70][71] Although there has been an increase in awareness of the importance of these micronutrient deficiencies due to their adverse health effects, there is a sparsity of information on deficiency prevalence 72 and thus estimating the prevalence of various micronutrient deficiencies and their respective anemia-attributable burden remains challenging. 52 In malaria-endemic countries, assessing malaria prevalence is warranted. Rapid diagnostic tests are inexpensive (cost approximately 1 US$) and are easy to administer.…”

“…The GBD 2019 study estimates the proportion of total anemia prevalence attributable to 35 causes based on cause‐specific hemoglobin shifts, the estimated prevalence of known causes, and the overall hemoglobin distribution for each location, year, and population group from 1990 to the present 47 . Because of the data sparsity, the GBD study does not use indicators of iron status to estimate the prevalence of iron deficiency, instead, it relies on counterfactual modeling and attempts to isolate the disease burden due to iron deficiency using hemoglobin as a proxy 52 . Systematic data collection of various causes and risk factors of anemia from population‐representative surveys could contribute to a better understanding of the complex interplay of causes and risk factors associated with the occurrence of anemia.…”

“…While deficiencies of some micronutrients (such as vitamins B 6 , C, D, E, copper, selenium, and zinc) may not contribute much to the global anemia burden, deficiencies in vitamins A, B 2 , B 12 , and folate could potentially be important in some contexts 16 , 68–71 . Although there has been an increase in awareness of the importance of these micronutrient deficiencies due to their adverse health effects, there is a sparsity of information on deficiency prevalence 72 and thus estimating the prevalence of various micronutrient deficiencies and their respective anemia‐attributable burden remains challenging 52 …”