Risk of neurodegenerative dementia in asthma patients: a nested case-control study using a national sample cohort

Objectives: This study investigated the risk of neurodegenerative dementia following asthma.

Design: A nested case-control study SETTING: The ≥60-year-old population was selected from the Korean Health Insurance Review and Assessment Service - National Sample Cohort from 2002 to 2013.

Participants and interventions: The 11 442 dementia cases were matched with 45 768 control cases for age, sex, income, region of residence, hypertension, diabetes and dyslipidaemia. Asthma was classified using International Classification of Disease-10 (ICD-10) codes (J45 and J46) and medication history. Dementia was identified based on ICD-10 codes (G30 and F00).

Primary and secondary outcome measures: The ORs of a previous history of asthma in patients with dementia were analysed using conditional logistic regression analysis stratified for age, sex, income, region of residence, hypertension, diabetes and dyslipidaemia. Subgroup analysis was performed according to age and sex.

Results: Overall, 22.6% (2587/11 442) and 22.3% (10 229/45 768) of the cases in the dementia and control groups, respectively, had a previous history of asthma. The OR for asthma in the dementia group was not higher than that in the control group (adjusted OR=0.97, 95% CI 0.92 to 1.02, p=0.207). All age and sex subgroups demonstrated consistent results.

Conclusions: Asthma was not related to an increased risk of dementia.