Adult asthma increases dementia risk: a nationwide cohort study.

Background: Studies on the association between adult asthma and dementia are few. We investigated the risk of dementia in patients diagnosed with adult asthma compared with that of people without asthma who were age and sex matched to the study patients.

Methods: We used data from the National Health Insurance Research Database. A total of 12 771 patients with newly diagnosed asthma between 2001 and 2003 were evaluated and 51 084 people without asthma were used as the comparison cohort. Cox proportional hazard regression analysis was used to measure the HR of dementia for the asthmatic cohort, compared with that of the non-asthmatic cohort.

Results: The HR of dementia was 1.27 (95% confidence interval (CI) 1.15 to 1.41) for the asthmatic cohort, compared with the non-asthmatic cohort after adjusting for age, sex, comorbidities, annual outpatient department visits and medicine used. The HR of dementia development increased substantially as frequency of asthma exacerbation and hospitalisation increased.

Conclusions: This nationwide cohort study suggests that the risk of dementia development is significantly increased in patients with asthma compared with that of the general population. In addition, dementia risk increases substantially with asthma exacerbation and hospitalisation frequency increases.