Alzheimer incidence and prevalence with and without asthma: A Medicare cohort study.
Level 3 - non-randomized controlled study
Retrospective observational cohort study using administrative claims data
PubMed 38670235 · doi:10.1016/j.jaci.2024.04.008
What was done
Researchers analyzed a 20% random sample of national Medicare beneficiaries (2013–2015) with over 12 months of continuous enrollment. Adult patients with asthma (defined by 1 inpatient or 2 outpatient diagnostic codes) were compared with individuals without asthma, both overall and in a matched analysis. The primary outcomes were 2-year claims-based incident or prevalent Alzheimer disease (AD) identified by ICD-9 and ICD-10 diagnostic codes.
What was found
Among 5,460,732 beneficiaries, 678,730 had baseline asthma. Patients with asthma had a 2-year AD incidence of 1.4% compared with 1.1% in those without asthma, and an AD prevalence of 7.8% versus 5.4% (both P ≤ .001), corresponding to 303 excess incident cases and 2,425 excess prevalent cases per 100,000 individuals over 2 years. In multivariable models, asthma was associated with higher odds of 2-year incident AD (adjusted OR 1.33, 95% CI 1.29–1.36; matched OR 1.20, 95% CI 1.17–1.24) and prevalent AD (adjusted OR 1.48, 95% CI 1.47–1.50; matched OR 1.25, 95% CI 1.22–1.27).
Why it matters
This study provides large-scale population evidence linking asthma to a modestly increased risk of Alzheimer disease, supporting the hypothesis that systemic inflammatory conditions may contribute to neurodegenerative disease risk.
Limits
The study relied strictly on administrative billing codes for asthma and Alzheimer disease without clinical or biomarker confirmation. The follow-up duration was short (2 years), raising the potential for reverse causality or surveillance bias, and residual confounding from unmeasured socioeconomic or lifestyle factors may remain.
Cited by
- supports Having asthma increases the risk of Alzheimer's disease by 20%.