Alzheimer’s Incidence and Prevalence with and without Asthma: A Medicare cohort study

Background International data suggest that asthma, like other inflammatory diseases, might increase Alzheimer’s disease (AD) risk. Objective To explore risk pathways and future mitigation strategies by comparing diagnostic claims-based AD incidence and prevalence among US patients with asthma to non-asthma patients. Methods This cohort study included a national Medicare 20% random sample 2013-2015. Adult patients with >12 months continuous Medicare with asthma were compared to non-asthma subjects overall and as matched. Asthma was defined by one inpatient or two outpatient codes for asthma. The main outcomes were two-year incident or prevalent AD defined as any codes for ICD-9 331.0 or ICD-10 G30.0, G30.1, G30.8, G30.9. Results Among 5,460,732 total beneficiaries, 678,730 patients were identified with baseline asthma and more often identified as Black or Hispanic, were Medicaid eligible, or resided in a highly disadvantaged neighborhood than those without asthma. Two-year incidence of AD was 1.4% with asthma vs 1.1% without; prevalence was 7.8% vs 5.4% (both p=<0.001). Per 100,000 patients over two years, 303 more incident AD diagnoses occurred in asthma, with 2,425 more prevalent cases (p<0.001). Multivariable models showed asthma had greater odds of two-year AD incidence [AOR 1.33 (1.29-1.36); matched 1.2 (1.17-1.24)] and prevalence [AOR 1.48 (1.47-1.50); matched 1.25 (1.22-1.27)). Conclusion Asthma was associated with 20-33% increased two-year incidence and 25-48% increased prevalence of claims-based Alzheimer’s disease in this nationally representative US sample. Future research should investigate risk pathways of underlying comorbidities and social determinants, as well as whether there are potential asthma treatments that may preserve brain health.