# Instability of Global Burden of Disease Estimates of Deaths and Disability-Adjusted Life-Years From Major Risk Factors: A Meta-Epidemiological Analysis

## TL;DR

This study finds that Global Burden of Disease estimates for deaths and disability from risk factors like diet are highly unstable over time, likely due to method changes rather than real health shifts.

## Contribution

The study introduces a meta-epidemiological analysis to quantify instability in GBD risk factor estimates across multiple iterations.

## Key findings

- Half of GBD death and DALY estimates had a coefficient of variation exceeding 0.2 across iterations.
- 70-96% of dietary risk point estimates in GBD 2021 fell outside the 2019 uncertainty intervals.
- Dietary and behavioral risk estimates showed the highest instability compared to other risk categories.

## Abstract

How stable and consistent are the Global Burden of Disease (GBD) estimates for mortality and disability-adjusted life-years (DALYs) that are attributable to major risk factors from 2010 to 2023?

This meta-epidemiological assessment comparing estimates across 8 iterations of GBD found substantial instability in behavioral risk, particularly dietary risks. Comparing revised estimates across iterations, half of the estimates had a coefficient of variation exceeding 0.2, and one-third of estimates for dietary risks in GBD 2021 fell outside the corresponding GBD 2019 uncertainty intervals.

GBD risk factor estimates, especially for behavioral and dietary risks, show marked inconsistency likely reflecting methodologic or data changes rather than true burden shifts.

The Global Burden of Disease (GBD) reports widely used estimates of mortality and disability-adjusted life-years (DALYs) and related risk factors. However, the overall reliability of these estimates between GBD iterations has not been assessed.

To evaluate the instability and inconsistency of GBD risk factor estimates for mortality and DALYs across GBD iterations.

GBD risk factor collaboration estimates extracted from the published tables of GBD iterations and the Institute for Health Metrics and Evaluation repository.

GBD risk factor collaboration publications published for 2010 through 2023.

Death and DALY estimates were manually extracted by 1 reviewer with independent validation of a random sample of 100 by another with no discrepancies. Risk factor naming was harmonized across iterations to ensure comparability; those with inconsistent definitions were excluded.

Fluctuations were calculated for numbers of deaths and DALYs for each risk factor across GBD iterations during the study period (2010-2023) and between the original and subsequently revised estimates for each year (1990-2021). Differences were expressed as a ratio of the minimum to maximum range to the mean (R:M) and coefficient of variation. Detail analyses assessed diet and low physical activity. Point estimates were compared to the previous iterations’ estimates 95% uncertainty intervals (95% UI) for GBD 2019, 2021, and 2023.

Across GBD iterations from 2010 to 2023, the median (range) R:M was 0.8 (0-3.8) for deaths, and 0.7 (0.1-3.3) for DALYs. Level 2 dietary and child and maternal malnutrition death estimates showed high instability (R:M >1 for 9 of 16 and 4 of 8 risks, respectively). When comparing original estimates with GBD 2019, 2021, and 2023 estimates for the same years, the median R:M was 0.4 (0-2.9) for both deaths and DALYs. The coefficient of variation was greater than 0.2 for 336 of 675 death estimates (50%). Specifically, 70% to 96% of point estimates for red meat, sugar-sweetened beverages, fruits, vegetables, and seafood omega-3 fatty acids in GBD 2021 fell outside the GBD 2019 95% UI. In GBD 2023, only diet high in trans fats had more than half of point estimates outside the GBD 2021 95% UI.

This meta-epidemiological assessment indicates that GBD estimates are substantially unstable, particularly for behavioral risks, making them unlikely to simply reflect genuine changes over time, and warranting caution in interpretation.

This meta-epidemiological assessment evaluates the reliability of the Global Burden of Disease risk factor estimates for mortality and disability-adjusted life-years.