Asthma, eczema, rhinitis and the risk for dementia

Inflammation is associated with Alzheimer's disease (AD) and dementia. In light of the chronic inflammatory properties of the atopic disorders asthma, eczema and rhinitis, we hypothesized an association with dementia.

Self-reported asthma, eczema or rhinitis was assessed (prior to dementia follow-up) through questionnaires in the 1960s or 1970s in twins from the population-based Swedish Twin Registry. Dementia was assessed both longitudinally (n = 22,188), through linkages to two population-based registers, and cross-sectionally (n = 7,800), through telephone cognitive screening followed by a clinical evaluation of suspects of dementia. Risk ratios were estimated with Cox and logistic regression models controlling for vascular disease and genetic confounding.

In the longitudinal study, a history of atopy was positively associated with dementia (HR = 1.16; 1.01-1.33). In the cross-sectional study we found overall lower risks, none of which was statistically significant. Asthma was associated with a shorter survival time following AD onset.

Atopy is associated with a modestly increased risk of AD and dementia that is not mediated by vascular disease or due to genetic confounding. A history of asthma is associated with shorter life expectancy after AD diagnosis.