Risk of All-Cause Mortality in US Adults With Preserved Ratio Impaired Spirometry: An Observational Study

Background: Preserved ratio impaired spirometry (PRISm) is defined as forced expiratory volume in one second (FEV1)/forced vital capacity (FVC)>= 0.70 and FEV1< 80% predicted. Previous studies have shown that individuals with PRISm may develop airflow obstruction and have an increased mortality risk. However, studies with long-term follow-up are lacking, and this topic has not been evaluated in the general population. We explored the all-cause mortality risk of individuals with PRISm in a large sample of the general population.<br /> Methods: We used data from the National Health and Nutrition Examination Survey III and 2007- 2012. Participants aged 20- 79 years at baseline and who underwent spirometry were included. Normal spirometry was defined as a prebronchodilator FEV1/FVC >= 0.70 and FEV1 >= 80% predicted. We used Cox proportional hazards regression models to compare all-cause mortality between the groups. We performed sensitivity analyses stratified by the lower limit of normal definition of spirometry criteria. Subgroup analyses by sex, age, smoking status, race, body mass index, level of education, poverty-to-income ratio, respiratory symptoms, and comorbidities were performed in participants with the different spirometry classifications.<br /> Results: Overall, 24,691 participants were included, with a median follow-up time of 25.7 years. Of these, 19,969 had normal spirometry and 1,452 had PRISm. PRISm was associated with a high all-cause mortality risk (unadjusted hazard ratio [HR]=2.47, 95% confidence interval [CI]: 2.25- 2.71, P< 0.001; adjusted HR=1.69, 95% CI: 1.54- 1.86, P< 0.001) compared with normal spirometry. Sensitivity analyses and subgroup analyses showed a similar increased all-cause mortality risk in PRISm.<br /> Conclusion: Our finding revealed that PRISm was significantly associated with increased risk of all-cause mortality in the general population compared with normal spirometry. Further research is needed to explore the intervention effect of PRISm.