Asthma Linked to Increased Dementia Risk

Asthma is significantly associated with an increased risk of all-cause dementia, but those who have all 3 allergic triad diseases are at the highest risk, according to a recent study.

Hee-Kyung Joh, MD, MPH, PhD, of the Seoul National University College of Medicine, the Seoul National University Health Service Center, and the Seoul National University Hospital, and colleagues conducted the study. The researchers published their findings in Annals of Neurology.

The study included 6,785,948 adults aged ≥ 40 years who did not have a prior history of dementia. Researchers prospectively investigated the associations between physician-diagnosed asthma, allergic rhinitis, and atopic dermatitis, and the risk of all-cause dementia, Alzheimer’s disease, and vascular dementia. Each patient received an initial medical examination in 2009, and researchers prospectively collected data on patients from 2009 to 2017 using national health insurance claims data.

The researchers identified 260,705 cases of dementia, including 195,739 cases of Alzheimer’s disease and 32,789 cases of vascular dementia, during 8.1 years of follow-up. The risk of all-cause dementia was greater in patients with asthma than in patients without allergic diseases (multivariable hazard ratio [HR], 1.20; 95% CI, 1.19-1.22). The risk of all-cause dementia was also greater in patients with allergic rhinitis (multivariable HR, 1.10; 95% CI, 1.09-1.12) and patients with atopic dermatitis (multivariable HR, 1.16; 95% CI, 1.11-1.21) than in patients without allergic diseases.

Patients with any of the 3 allergic diseases had a higher risk of developing Alzheimer’s disease (HR, 1.16; 95% CI, 1.14-1.17) or vascular dementia (HR, 1.04; 95% CI, 1.01-1.06) than patients without any allergic disease.

Patients who had asthma, allergic rhinitis, and atopic dermatitis had an increased risk of all-cause dementia (HR, 1.54; 95% CI, 1.35-1.75), Alzheimer’s disease (HR, 1.46; 95% CI, 1.25-1.70), and vascular dementia (HR, 1.99; 95% CI, 1.44-2.75) compared with those who did not have an allergic disease. There was a linear relationship between the number of comorbid allergic diseases and the risk of dementia, with the risk of dementia rising with the number of comorbid allergic diseases.

“Asthma, allergic rhinitis, and atopic dermatitis were significantly associated with increased risk of all-cause dementia and subtypes, with dose-effect relationships with the severity of allergic diseases,” the researchers concluded.

Joh HK, Kwon H, Son KY, et al. Allergic diseases and risk of incident dementia and Alzheimer’s disease. Ann Neurol. 2022. doi:10.1002/ana.26506