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

Importance: 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. Objective: To evaluate the instability and inconsistency of GBD risk factor estimates for mortality and DALYs across GBD iterations. Data Sources: GBD risk factor collaboration estimates extracted from the published tables of GBD iterations and the Institute for Health Metrics and Evaluation repository. Study Selection: GBD risk factor collaboration publications published for 2010 through 2023. Data Extraction and Synthesis: 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. Main Outcomes and Measures: 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. Results: 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. Conclusions and Relevance: 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.