In patients with nonobstructive lung function abnormalities — otherwise known as preserved ratio impaired spirometry (PRISm) — baseline values were moderately correlated with increased risk of death, as well as negative cardiovascular and respiratory outcomes. These and other findings were described in a recent population-based study of US adults published in Journal of the American Medical Association.
PRISm is characterized by symmetric reductions in both forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC). Clinical outcomes associated with these proportional reductions in expiratory lung volumes without obstruction remain to be elucidated.
The central question addressed in this study was whether PRISm — defined as the ratio of a forced expiratory volume in 1 second to forced vital capacity ratio (FEV1:FVC) greater than or equal to 0.7, with an FEV1 less than 80% predicted — was associated with adverse clinical outcomes. Researchers mined data from the National Heart Lung and Blood Institute (NHLBI) Pooled Cohorts Study, which spanned 9 diverse population-based samples. They determined the prevalence and correlates of PRISm and investigated whether PRISm was associated with increased odds of cardiovascular-related and respiratory-related hospitalization and death than was normal spirometry.
From the dataset of 53,701 adult patients with valid baseline lung function, researchers identified 4582 (8.5%) with PRISm. When compared with normal spirometry, PRISm was significantly associated with all-cause mortality (adjusted HR: 1.50); respiratory-related mortality (adjusted HR: 1.95), coronary heart disease (CHD)-related mortality (adjusted HR: 1.55), respiratory-related hospitalizations and mortality (adjusted HR: 1.90), and CHD-related hospitalizations and mortality (adjusted HR: 1.30). In other findings, the presence of PRISm at baseline was associated with obesity, underweight status, female sex, and current smoking.
Previous research has suggested that the prevalence of PRISm varied by geography, race, and ethnicity. In the current study, the unadjusted prevalence of PRISm was higher in marginalized/underserved communities, but after further analysis, no differences were observed in those of different races or ethnicities.
This study had certain limitations. For instance, postbronchodilator spirometry could have led to an overestimation of the prevalence of both PRISm and obstructive lung disease. Furthermore, it is possible that certain respiratory and CHD-related hospitalizations were improperly classified. Notably, although this large cohort was racially and ethnically diverse, it included only adults residing in the US; thus, results may not be applicable to a global population.
The investigators concluded that “In a large, population-based sample of US adults, baseline PRISm, compared with normal spirometry, was associated with a small but statistically significant increased risk for mortality and adverse cardiovascular and respiratory outcomes. Further research is needed to explore whether this association is causal.”
Wan ES, Balte P, Schwartz JE, et al. Association between preserved ratio impaired spirometry and clinical outcomes in US adults. JAMA. 2022;327(3):286. doi:10.1001/jama.2021.20939