Risks of Dementia in a General Japanese Older Population With Preserved Ratio Impaired Spirometry: The Hisayama Study

Background: Studies on the association between preserved ratio impaired spirometry (PRISm) and dementia are limited. Indeed, PRISm has often been overlooked or ignored as an index of lung function impairment. Therefore, we investigated the association of PRISm with the risk for the development of dementia in an older Japanese population. Methods: A total of 1,202 community-dwelling, older Japanese participants aged ≥65 years without dementia were followed up for a median of 5.0 years. Participants were categorized by spirometry as follows: normal spirometry (FEV₁/FVC ≥0.70 and FEV₁ ≥80% predicted), PRISm (≥0.70 and <80%), airflow limitation (AFL) Global Initiative for Chronic Obstructive Lung Disease (GOLD) 1 (<0.70 and ≥80%), and AFL GOLD 2 to 4 (<0.70 and <80%). Hazard ratios (HRs) and their 95% confidence intervals (CIs) were computed using a Cox proportional hazards model. Results: During the follow-up period, 122 participants developed dementia. The age-and sex-adjusted incidences of dementia in the participants with normal spirometry, PRISm, AFL GOLD 1, and AFL GOLD 2 to 4 were 20.5, 37.0, 18.4, and 28.6 per 1,000 person-years, respectively. Participants with PRISm had a higher risk of dementia (HR 2.04; 95% CI, 1.19–3.49) than those with normal spirometry after adjusting for confounders. Moreover, both reduced FEV₁% predicted values and FVC% predicted values were associated with the risk of dementia. Conclusion: PRISm was associated with an increased risk of dementia in a general older Japanese population.