Investigating Epidemiologic and Geospatial Patterns of Alzheimer’s Disease in the Medicare Population Across the United States
George Karway1, Irene Faust1, Brad Racette1, Brittany Krzyzanowski1
1Neuroepidemiology, Barrow Neurological Institute, Dignity Health | St. Joseph's Hospital and Medical Center
Objective:
To investigate epidemiologic and geospatial patterns of Alzheimer’s disease (AD) in the Medicare population
Background:
As the “baby boomer” generation ages, neurodegenerative diseases like AD will become more common and estimates of the disease burden are critical. Moreover, understanding the impact of cardiometabolic diseases (CMD) on incident AD can inform primary prevention measures.
Design/Methods:
We conducted a population-based epidemiologic and geospatial analysis of 21,475,504 Medicare beneficiaries from 2014 to 2019. We computed county-level national AD incidence and used R-project’s integrated nested Laplace approximation (R-INLA) to adjust for age, race, and sex within our county-level AD map. We used data from the Chronic Conditions Warehouse to create a map of prevalent CMD from data on acute myocardial infarction, chronic obstructive pulmonary disease, congestive heart failure, diabetes, ischemic heart disease, and stroke. We also mapped two other AD risk factors, smoking and educational attainment. We examined the similarities of spatial patterns between our AD map and maps of CMD, educational attainment, and smoking using Mapcurves (MC)—a goodness-of-fit method that quantifies the degree of spatial concordance between two categorical maps using a 0 to 1 scale where higher values represent greater similarity. We visualized map similarity using bivariate local indicators of spatial association (biLISA).
Results:
We found strong nationwide agreement between spatial patterns of incident AD and CMD (MC = 1.0) and moderate alignment of AD and smoking (MC = 0.75). There was weak, inverse map alignment between AD and educational attainment (MC = 0.5). Our biLISA maps corroborated these results and further demonstrated areas of interest for investigating environmental or genetic risk factors of AD (i.e., regions which were AD hot spots and cardiometabolic disease cold spots).
Conclusions:
We demonstrated a very strong relation between AD and CMD, particularly in the Southern U.S., suggesting that targeted primary prevention could substantially reduce disease incidence.