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

Background: The Global Burden of Disease (GBD) Study provides estimates of death and disability from eighty-seven risk factors, including some micronutrient deficiencies. Objectives: To review methodological changes that led to large differences in the disease burden estimates for vitamin A and Zn deficiencies between the GBD 2017 and 2019 Studies. Methods: GBD publications were reviewed; additional information was provided by GBD researchers. Results: Vitamin A deficiency prevalence is based on plasma retinol concentration, whereas the estimate for Zn deficiency prevalence uses dietary adequacy as a proxy. The estimated global prevalence of vitamin A deficiency for children aged 1-4 years in the year 2017 decreased from 0 center dot 20 (95 % CI 0 center dot 17, 0 center dot 24) in GBD 2017 to 0 center dot 16 (95 % CI 0 center dot 15, 0 center dot 19) in GBD 2019, while the global prevalence of Zn deficiency did not change between the two studies (0 center dot 09 (95 % CI 0 center dot 04, 0 center dot 17) and 0 center dot 09 (95 % CI 0 center dot 03, 0 center dot 18)). New to 2019 was that meta-analyses were performed using Meta Regression - Bayesian, Regularized, Trimmed, a method developed for GBD. Due to this and multiple other methodological changes, the estimated number of deaths due to vitamin A deficiency dropped from 233 000 (179 000-294 000) to 24 000 (3000-50 000) from GBD 2017 to 2019, and for Zn deficiency from 29 000 (1000-77 000) to 2800 (700-6500), respectively. Conclusion: The changes in the estimated disease burdens due to vitamin A and Zn deficiencies in the GBD reports from 2017 to 2019 are due primarily to changes in the analytical methods employed, so may not represent true changes in disease burden. Additional effort is needed to validate these results.

Automated summary

The Global Burden of Disease (GBD) Study shows significant changes in the estimated disease burden due to vitamin A and zinc deficiencies from 2017 to 2019, primarily due to changes in analytical methods, which may not represent true changes in disease burden. Further efforts are needed to validate these results.