Letter to the Editor in Response to “Z-Score Burden Metric: A Method for Assessing Burden of Injury and Disease”

In their article, Wolff and colleagues propose a new Z-score Burden Metric (ZSBM) for assessing burden of injury and diseases. They describe the new metric as “ZSBM compares age-specific rates with those of the state as a whole and then collapses them to depict the burden imposed on a county on the basis of its own age distribution rather than that of the reference population as in age-adjusted rates.” The ZSBM is used to generate 4 complementary measures to describe various components of overall burden. The authors’ primary focus is on assessing the burden of injury and disease as defined by incidence (not severity of illness, cost of illness, years of potential life lost, or any other relevant measure). They propose a new measure named the Overall Burden Measure (OBM) to assess such burden and then use it to analyze data from firearm-related injury deaths in North Carolina. They compare the results on the basis of the OBM versus the unadjusted and age-adjusted rates and summarize the findings in their Figure 1 (available through the link https://doi.org/10.1016/j.amepre.2022.03.029). They conclude that burden as measured by the OBM and the unadjusted rate are similar but not the same. Thus, an important question arises: What measure is appropriate when the OBM and the unadjusted rate give different results? I suggest that using the OBM versus the unadjusted rate for measuring the burden of a disease is problematic when these measures disagree (e.g., Onslow versus Moore, which shows one of the highest disagreements in their Figure 1, available through the link https://doi.org/10.1016/j.amepre.2022.03.029).