Generated Summary
This document is a correspondence discussing the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 results, specifically addressing concerns about the estimated deaths attributed to red meat intake. The authors, Alice Stanton and colleagues, raise questions about the substantial increase in these estimates compared to the GBD 2017 results. The response, by Christopher JL Murray on behalf of the GBD Risk Factors Collaborators, explains the methodological changes implemented in GBD 2019 and upcoming GBD 2020 revisions, and addresses the concerns raised. The study uses a systematic review and meta-analysis approach to assess the impact of diet on health outcomes. The document highlights the adoption of new systematic reviews, dose-response meta-regression methods, and the use of a star-rating system to assess the strength of evidence. It also clarifies the rationale behind the changes in the Theoretical Minimum Risk Exposure Level (TMREL) and the inclusion of new data and analytical approaches.
Key Findings & Statistics
- The document discusses a 36-fold higher estimate of deaths attributable to red meat intake in GBD 2019 compared to GBD 2017.
- The authors of the correspondence note concerns regarding the large increase in estimated deaths due to red meat intake in the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 results compared with the GBD 2017 results.
- The document refers to the GBD 2019 study, which analyzed 87 risk factors in 204 countries and territories from 1990-2019.
- The authors mention that in GBD 2019, the TMREL for red meat intake was estimated, and new risk functions were used.
- The study incorporated new systematic reviews and dose-response meta-regression methods.
- The document mentions that the GBD 2020 will include separate analyses for ischaemic stroke and haemorrhagic stroke.
- The increase in risk associated with red meat intake was not fully accounted for by the methodological changes in estimating risk functions.
- The GBD 2020 will introduce a five-star rating system to aid in interpretability of the strength of the evidence.
- The TMREL for protective risk factors was set to the 85th percentile of exposure in available studies.
- The GBD 2017 set the TMREL for harmful risks to the 15th percentile of exposure.
- The document notes the estimated protective effect of red meat on haemorrhagic stroke in GBD 2020, which will change the estimates of the TMREL.
- The document asserts that there are zero deaths attributable to red meat below the age of 25 years.
Other Important Findings
- The substantial increase in estimated deaths due to red meat intake is attributed to new risk functions, updated systematic reviews, and changes in the TMREL.
- The authors are introducing a five-star rating system in GBD 2020 to assess the strength of evidence.
- The document highlights the adoption of new systematic reviews and dose-response meta-regression methods.
- The document states that the new meta-regression methods better capture non-linear relationships in diet studies.
- The protective relationship between red meat intake and haemorrhagic stroke, which was not identified in the GBD 2019 analysis, will be reflected in the GBD 2020 findings.
- The authors acknowledge concerns regarding the potential for residual confounding in observational studies on diet.
- The document emphasizes the importance of standardizing methods to improve comparability and addresses the limitations in the GBD 2017.
- The document mentions that the GBD 2020 will conduct separate analyses for ischaemic stroke and haemorrhagic stroke.
- The authors address the value of meat as a protein source, particularly for children, noting that the GBD’s role is to follow the science on exposure levels associated with the lowest risk.
- The authors clarify that detailed citations for the sources used in the analysis of red meat are available in the GBD 2019 Data Input Sources Tool.
Limitations Noted in the Document
- The document acknowledges the inherent uncertainty in estimating risk functions, risk exposure, and the TMREL.
- The authors note the potential for residual confounding in observational studies on diet.
- The reliance on observational data for diet risk-outcome pairs is a limitation.
- The document mentions that the GBD estimates reflect uncertainty from the estimated risk functions, uncertainty in risk exposure, and uncertainty in the TMREL.
- The GBD estimates reflect uncertainty from the estimated risk functions, uncertainty in risk exposure, and uncertainty in the TMREL.
Conclusion
The correspondence provides a detailed response to the concerns raised about the significant increase in the estimated deaths attributable to red meat intake in the GBD 2019 results. The authors, Christopher JL Murray and the GBD Risk Factors Collaborators, emphasize the methodological changes implemented to improve the accuracy and standardization of the study. The shift in the TMREL, the incorporation of new data, and the use of advanced meta-regression techniques are key factors contributing to these changes. The introduction of the star-rating system aims to enhance the interpretability of the evidence supporting the analyses. While the document acknowledges the inherent uncertainty in the estimates and potential for confounding in observational studies, it stresses the importance of following scientific evidence to assess risk. The forthcoming GBD 2020 revisions, including separate analyses for different types of stroke and the consideration of the protective effects of red meat on haemorrhagic stroke, are expected to further refine the estimates. The authors maintain that the study’s focus is on the relationship between exposure levels and risk, rather than on balancing the overall dietary considerations, and reiterate that the results over age 25 years have no bearing on dietary recommendations for children. The response underscores the ongoing efforts to improve the methodology and address the concerns raised, highlighting the commitment to providing transparent and accurate health estimates, despite the complexities involved in dietary research and the associated controversies.