Preserved Ratio Impaired Spirometry (PRISm) Prevalence, Risk Factors, and Outcomes: A Systematic Review and Meta-Analysis.

Background: The prevalence of chronic respiratory diseases is increasing globally. There is evidence that those with spirometric impairment, and no evidence of obstruction, termed preserved ratio impaired spirometry (PRISm), have increased risk of morbidity and mortality, compared to those with normal lung function. There remain several gaps in characterizing PRISm.

Research questions: What is the prevalence, risk factors and clinical outcomes associated with PRISm globally?

Study design and methods: In this systematic review a comprehensive search using MEDLINE, Web of Science, CINHAL, and CENTRAL databases was conducted to include epidemiological studies with no language or data restrictions. Two reviewers independently screened citations and shortlisted full-text articles according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and data was extracted. Quality was assessed with the Effective Public Health Practice Project tool.

Results: 52 studies met the inclusion criteria with 33 studies included in the meta-analysis. Pooled PRISm prevalence was 12% (95% CI: 0.10, 0.15) with greater prevalence in low-and middle-income countries (LMICs) compared to high-income countries (19% vs. 11%). Comorbid diabetes was a significant risk factor associated with PRISm but data for female sex and smoking were mixed. PRISm was associated with increased all-cause (OR 1.41, 95% CI:1.08, 1.83, p=0.02), cardiovascular (OR 1.84, 95% CI:1.31, 2.58, p<0.01), and respiratory mortality (OR 1.82, 95% CI:1.08, 3.05, p=0.03). PRISm was not associated with a reduced lung cancer diagnosis (p=0.46). Quality assessment analysis revealed 34.6% (n=18) studies were rated "strong," 42.3% (n=22) "moderate," and 23.1% (n=12) "weak." Studies conducted LMICs had lower quality ratings.

Interpretation: Individuals with PRISm have increased risk of all-cause, cardiovascular, and respiratory mortality. Recognizing and targeting modifiable PRISm risk factors may reduce the growing burden of PRISm and transition to obstructive lung disease globally. Additional studies are needed in LMICs that have unique risk factors a disease trajectory.