Instability of Global Burden of Disease Estimates of Deaths and DALYs from Major Risk Factors

Abstract Importance The Global Burden of Disease (GBD) study provides widely used estimates of mortality and disability-adjusted life years (DALYs) attributable to risk factors. Objective To evaluate the variability and consistency of GBD risk factor estimates for mortality and DALYs. Data Sources GBD Risk Factor collaboration estimates extracted from published tables and IHME repository. Study Selection GBD Risk Factor collaboration publications (2010-2023). Data Extraction and Synthesis Death and DALY estimates were manually extracted by one 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 We calculated the fluctuations in deaths and DALYs for each risk factor across GBD iterations for different years (2010-2023), and between the original and subsequently revised estimates for each year (1990-2021) expressed in the ratio of the min-max range to the mean (R/M) and coefficient of variation (CV). We examined in more detail analyses diet and low physical activity. Finally, 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 R/M was 0.8 (range, 0–3.8) for deaths, and 0.7 (range, 0.1–3.3) for DALYs. Among level 2 dietary and child and maternal malnutrition death estimates showed high variability (R/M>1 for 7/16 and 3/8 of risks, respectively). When comparing original estimates with GBD 2019, 2021, and 2023 estimates for the same years, the median R/M was 0.5 (0.0-2.9) for deaths and 0.4 (0-2.9) for DALYs. The CV was above 0.2 for 320/580 (52%) of death and 306/609 of DALY estimates. 70-96% 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 over half of point estimates outside the GBD 2021 95%UI. Conclusions and Relevance GBD estimates show large instability, particularly for behavioral risks, making them unlikely to simply reflect genuine changes over time, and warranting caution in interpretation. Key Points Question How stable and consistent are the Global Burden of Disease (GBD) estimates for mortality and disability-adjusted life years (DALYs) attributable to major risk factors across iterations from 2010 to 2023? Findings In this study comparing estimates across eight GBD iterations, substantial variability was observed. Behavioral, particularly dietary risks showed the greatest instability. Comparing revised estimates across iterations half the estimates had a coefficient of variation exceeding 0.2. A third of estimates for dietary risks in GBD 2021 fell outside the corresponding GBD 2019 uncertainty intervals. Meaning GBD risk factor estimates, especially for behavioral and dietary risks, show marked inconsistency likely reflecting methodological or data changes rather than true burden shifts.