Methodological concerns regarding mortality trends in CVD and Alzheimer's disease comorbidity

Methodological concerns regarding mortality trends in CVD and Alzheimer's disease comorbidityTo the Editor,We read with interest the article by Wen et al. [1] examining mortality trends for cardiovascular disease and Alzheimer's disease comorbidity in older U.S. adults using the CDC WONDER database.The authors address a topic of substantial public health importance, and the use of a comprehensive national mortality database is commendable.However, several methodological and presentational issues compromise the clarity and reliability of the reported findings, and we wish to highlight these concerns for the benefit of readers.A primary issue lies in the description of the study population.In the Methods section, the authors refer to "a nationally representative cohort of 10,000 participants" used to analyze mortality patterns.This is inconsistent with the actual study design, which draws from the full CDC WONDER multiple-cause-of-death database and encompasses over 1.2 million deaths.The mention of a 10,000-participant cohort misrepresents the scope of the analysis and should be corrected to reflect the population-based nature of the data.Additionally, while the authors note that crude mortality rates were calculated per 100 population, all age-adjusted mortality rates presented in the figures, tables, and results are reported per 100,000.This distinction is appropriate, but the text would benefit from greater clarity to avoid any potential confusion among readers regarding the denominators used.A second and equally concerning methodological flaw pertains to the urbanization analysis.CDC WONDER urbanization classification data are available only through 2020.In the supplementary material, the authors note that "The AMMR data for urbanization classification in 2023 is from 2020, and AAPC calculates it from 1990 to 2023."This means that the 2023 age-adjusted mortality rates for metropolitan and nonmetropolitan areas are actually based on 2020 data, and the average annual percent changes are calculated over a time frame that extends three years beyond the last actual observation.This practice is methodologically indefensible, as it artificially projects trends and misleads readers about the true temporal scope of the analysis.The urbanization results should be reported only through 2020, and all references to "2023" in the urbanization section, including the legend of Fig. 5, must be corrected accordingly.Additional data presentation errors further detract from the study's credibility.In the census region analysis, the annual percentage change for the West from 2004 to 2014 is reported as "-0.78 (95% CI: -1.84 to 70.29)."The upper confidence limit of 70.29 is implausible and likely a typographical error; it should probably read 0.29.Similar improbable confidence intervals appear elsewhere, suggesting that the Joinpoint regression outputs were not carefully transcribed.In the age-stratified analysis, the values for the 65-74, 75-84, and 85+ age groups are presented as age-adjusted mortality rates but have identical lower and upper confidence bounds.The supplementary table footnote clarifies that crude mortality was used for these age groups.Labeling crude rates