Spirometry-defined obstructive airflow limitation and risk of incident dementia: A nationwide cohort study in South Korea.

BackgroundWhether spirometry-defined airflow limitation is independently associated with incident dementia and related disability burden remains unclear.ObjectiveTo investigate the association between obstructive airflow limitation and incident dementia and to estimate dementia-related years lived with disability (YLDs) in a nationwide cohort.MethodsWe conducted a nationwide population-based cohort study linking the Korea National Health and Nutrition Examination Survey (2014-2021) with national health insurance claims data. Adults aged ≥40 years with baseline spirometry and no prior dementia were included. Airflow limitation was defined as FEV1/FVC <0.70, with severity classified by percent-predicted FEV1. Inverse probability of treatment weighting balanced baseline covariates. Cox models estimated adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) for incident dementia. Dementia-related YLDs were calculated using Global Burden of Disease Study weights.ResultsDuring follow-up (2014-2023), 760 cases (4.79%) of dementia occurred among 15,854 adults. Normal pulmonary function was associated with lower dementia risk than airflow limitation (aHR, 0.62 [95% CI, 0.50-0.77]). Within the normal range, risk decreased across increasing FEV1/FVC tertiles (T1 [lowest], 0.76 [0.60-0.96]; T2, 0.63 [0.49-0.81]; T3 [highest], 0.45 [0.34-0.59]). Among those with airflow limitation, risk increased with severity (mild: 1.32 [0.95-1.84]; moderate: 1.87 [1.41-2.46]). Greater severity was also associated with higher YLDs.ConclusionsSpirometry-defined airflow limitation was associated with higher dementia risk and greater disability burden, suggesting impaired pulmonary function as a potential factor in dementia risk stratification and brain health.