Using a newly validated algorithm to estimate prevalence and incidence of Alzheimer’s Disease and related dementias in Medicare claims

Abstract

AbstractBackgroundFew published studies have estimated the prevalence and incidence of Alzheimer’s disease (AD) and AD related dementias (ADRD) in the US Medicare population using fit‐for‐purpose claims algorithms. This study utilized a newly validated administrative claims algorithm for identifying ADRD, the “1‐year Bynum‐Standard ADRD algorithm”, adjusted for positive predictive value (PPV) and sensitivity, to estimate the 2019 annual prevalence and annual incidence of ADRD in US Medicare patients 65+ years of age.MethodsThis study utilized Medicare Part A and B claims (Fee‐For‐Service and Medicare Advantage) limited to patients with at least one 2019 medical encounter. The study’s source population was limited to those 65+ years of age with Medicare Part D coverage and 1‐year pre‐encounter continuous enrollment. Utilizing the 1‐year Bynum‐Standard ADRD claims algorithm, patients with ADRD were compiled. As the Brynum‐Standard algorithm includes AD as well as related dementias, a second AD cohort was built adapting the algorithm’s code list to include only specific AD diagnoses. Prevalence was calculated as a percent of the source population after adjustment for PPV and sensitivity of the algorithm. Incidence calculations required a 1‐year pre‐diagnosis exclusion period.ResultsFrom 53.9 million Medicare patients with at least one 2019 medical encounter, 33.3 million patients qualified for the source population. Of these patients, 2.7 million (8.0%) qualified as having ADRD using the 1‐year Bynum‐Standard algorithm and 0.86 million of these patients (32.2%) were newly diagnosed (incident). After adjusting for 31.3% sensitivity and 70.3% PPV of the algorithm the estimated 2019 annual prevalence and incidence of ADRD in the Medicare population aged 65 or older was 18% and 5.8% respectively. When limited to patients with specific AD diagnoses only, 1.0 million prevalent and 0.37 million incident patients were identified resulting in an annual adjusted prevalence and incidence of 6.9% and 2.5% respectively. Prevalence and incidence calculations including adjustments are provided in figure 1.ConclusionUsing a fit‐for‐purpose validated algorithm, the 2019 annual prevalence and incidence of ADRD in the Medicare population aged 65+ with Part D enrollment was estimated to be 18% and 5.8% respectively.