Letter to the Editor: "Global, regional, and national burden of malignant neoplasm of bone and articular cartilage in adults aged 65 years and older, 1990-2021: a systematic analysis based on the global burden of disease study 2021".

The recent publication by Zhang et al. on the burden of malignant neoplasm of bone and articular cartilage in the geriatric population reports age-standardized incidence, prevalence, disability-adjusted life year (DALY), and mortality rates. The authors present age-standardized rates for the 6+ age group based on the Global Burden of Disease (GBD) 2021 study. However, calculating age-standardized measures for a single age group is methodologically inconsistent and may lead to misinterpretation. These measures are designed to compare populations with varying age distributions by applying a uniform age structure. Thus, the GBD 2021 study only offers age-standardized rates for total populations, not specific age groups. Moreover, the 65 + group is not among the predefined age groups in the GBD 2021 study for any health measures. While crude numbers for custom age groups, such as individuals aged 65 years and older, can be derived from the available data, estimating incidence, prevalence, DALY or mortality rates requires complex calculations that cannot be reproduced externally. These limitations raise notable concerns about the reliability of the reported measures and their interpretation.