Identification of older adults with Alzheimer's and related dementias among patients newly diagnosed with cancer: A comparison of methodological approaches.

introductionResearch efforts to characterize and evaluate care delivery and outcomes for older adults with cancer and comorbid dementia are limited by varied methods used to classify Alzheimer's disease and related dementias (ADRD). The purpose of this study is to evaluate differences in demographic, clinical, and cancer characteristics of people newly diagnosed with cancer and concomitant dementia comparing two common methods to identify ADRD using administrative claims data. MATERIALS AND

methodsWe conducted a retrospective cohort study using Surveillance, Epidemiology, and End Results (SEER)-Medicare data. Our sample included adults aged 66 years and older with a first primary diagnosis of lung or colorectal cancer between 2011 and 2017. For each cancer diagnosis, we constructed analytical cohorts using the Center for Medicare and Medicaid Services' Chronic Condition Warehouse (CCW) flag and the Bynum-Standard one- and three-year algorithms to capture diagnosed ADRD. We estimated ADRD prevalence using the algorithms and compared Bynum and CCW cohorts on demographic, clinical, and cancer characteristics at cancer diagnosis and survival for lung and colorectal cancer separately.

resultsAmong older adults with lung cancer, ADRD prevalence was 4.7% with the one-year Bynum, 6.5% with the three-year Bynum, and 12.5% using the CCW flag. In the colorectal cohort, ADRD prevalence was 5.6% with the one-year Bynum, 7.6% with the three-year Bynum, and 14.1% with the CCW flag. Demographic characteristics were similar across ADRD cohorts. The Bynum cohorts identified higher proportions of individuals with moderate to severe dementia (13.8% and 11.2% versus 7.1% CCW in lung cancer; 13.1% and 10.6% versus 6.8% CCW in colorectal cancer), higher frailty rates (27.4% and 22.7% versus 15.0% CCW in lung cancer; 26.4% and 22.3% versus 14.8% CCW in colorectal cancer). Median survival was lower for the Bynum cohorts compared to the CCW, regardless of cancer type. DISCUSSION: Findings demonstrate that ADRD prevalence and certain clinical characteristics vary based on dementia ascertainment method and observation period used to classify individuals with ADRD. Considering differences in the cohorts of registry cases generated by the identification method used is essential when interpreting findings related to treatment, utilization, and outcomes within and across cancer cohorts.