Lung function trajectories and exacerbation risks in preserved ratio impaired spirometry (PRISm) patients

Preserved ratio impaired spirometry (PRISm) is a heterogeneous, clinically relevant pre-chronic obstructive pulmonary disease (pre-COPD) state that remains incompletely understood. Recurrent exacerbations link to poor outcomes, but data on subtype-specific (lung function trajectory) exacerbation risk is scarce. This study assessed lung function trajectory changes and exacerbation risk in PRISm. We enrolled 204 PRISm patients and 501 individuals with normal lung function. Demographics, clinical features, and exacerbation events over the past year were evaluated. 204 PRISm patients were subsequently followed for one year, and categorized into three subgroups: PRISm-normal, persistent PRISm, and PRISm-COPD. Exacerbation events and lung function changes were analyzed. Univariate and multivariate logistic regression analyses were used to identify risk factors for exacerbation. PRISm patients had higher smoking prevalence, comorbidities, and symptom burden than controls (p < 0.05). The incidence of moderate and severe exacerbations and frequent exacerbations in PRISm patients were 1.8-fold (0.35 vs. 0.19, p < 0.001), 2.1-fold (0.17 vs. 0.08, p < 0.05), and 2.7-fold (10.3% vs. 3.8%, p < 0.001) higher than the normal group. The PRISm-COPD subgroup had the highest risk, with rates 3.7- to 7.7-fold higher than the normal group. Furthermore, persistent PRISm and PRISm-COPD subgroups showed significantly greater declines in forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and FEV1/FVC. After adjusting for confounders, the PRISm-COPD subgroup had a more pronounced FEV1 decline (− 27.2 ml/y vs. −30.5 ml/y, p < 0.001). Multivariate analysis showed that FEV1 decline was inversely associated with exacerbations in PRISm patients, whereas elevated C-reactive protein levels were positively correlated with exacerbation risk (p < 0.001). PRISm patients exhibit worse lung function and more frequent acute exacerbations, with the PRISm-COPD subtype predicting faster lung function decline. Worsening lung function and inflammation levels significantly increase exacerbation risk in PRISm patients.