Longitudinal Changes and Association of Respiratory Symptoms with Preserved Ratio Impaired Spirometry (PRISm): The Nagahama Study

Rationale: Subjects with preserved ratio impaired spirometry (PRISm) experience increased respiratory symptoms, although they present heterogeneous characteristics. However, the longitudinal changes in these symptoms and respiratory function are not well known. Objectives: To investigate PRISm from the viewpoint of respiratory symptoms in a longitudinal, large-scale general population study. Methods: The Nagahama study included 9,789 inhabitants, and a follow-up evaluation was conducted after 5 years. Spirometry and self-administered questionnaires regarding respiratory symptoms, including prolonged cough, sputum and dyspnea, and comorbidities were conducted. Results: In total, 9,760 subjects were analyzed, and 438 subjects had PRISm. Among the subjects with PRISm, 53% presented with respiratory symptoms; dyspnea was independently associated with PRISm. Follow-up assessment revealed that 73% of the subjects with PRISm with respiratory symptoms were consistently symptomatic, whereas 39% of the asymptomatic subjects with PRISm developed respiratory symptoms within 5 years. In addition, among subjects with respiratory symptoms without airflow limitation at baseline, PRISm was a risk factor for the development of airflow limitation independent of smoking history and comorbidities. Conclusions: This study demonstrated that 53% of the subjects with PRISm had respiratory symptoms; dyspnea was a distinct characteristic of PRISm. Approximately three-fourths of the symptomatic subjects with PRISm consistently complained of respiratory symptoms within 5 years. Together with our result that PRISm itself is an independent risk factor for the development of chronic obstructive pulmonary disease among subjects with respiratory symptoms, the clinical course of subjects with PRISm with symptoms requires careful monitoring.