Coding of Obesity-related Mortality Impacts Estimates of Obesity on U.S. Life Expectancy

Background High levels of obesity remain an important population health problem in the U.S. and a possible contributor to stalling life expectancy. However, reliable estimates of the contribution of obesity to mortality in the U.S. are lacking, because of inconsistent coding of obesity-related causes of death. Methods We compare five International Classification of Diseases version 10 (ICD-10) coding schemes for obesity-related mortality used in the literature and examine how the magnitude of obesity-related mortality burdens varies across different schemes. We use U.S. multiple cause of death data and population estimates for the Black, white, and Latino population in the years 2010, 2015, and 2020. In sex- and race/ethnic-stratified analyses, we estimate the potential years of life expectancy gained if obesity-related mortality had not occurred as measured by each coding scheme. Results We estimate that obesity-related mortality contributes to up to 78 months (6.5 years) of lost U.S. life expectancy, though estimates range from as low as 0 months, with a median contribution across ICD-10 coding schemes of about 20 months (1.7 years). Despite substantial variation across coding schemes, obesity-related mortality consistently contributes more to life expectancy deficits for Black Americans compared to white and Latino Americans. Across all ICD-10 coding schemes, the age pattern of obesity follows a J-shaped curve, suggesting exponential increases in obesity-related mortality after age 25. Conclusions The estimation of the burden of obesity-related mortality on life expectancy in the United States varies widely depending on the causes of death used in analyses. This inconsistency may obscure our understanding of the contribution of obesity-related mortality to trends in life expectancy. We propose a standardization of the coding of obesity-related mortality for future studies and outline which causes should be included. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement British Academy Newton International Fellowship grant NIFBA19/190679 (JMA) Rockwool Foundation Excess Deaths grant (JMA) Leverhulme Trust Large Centre Grant (JMA; AMT; JBD) European Research Council grant ERC-2021-CoG-101002587 (JBD; AMT) ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes The code, and all harmonized input and output data pertaining to our analysis, is hosted on GitHub https://github.com/OxfordDemSci/ex_USA.