Abstract
Background: The prevalence of chronic respiratory diseases is increasing globally. There is evidence that those with spirometric impairment and no signs of obstruction (termed preserved ratio impaired spirometry [PRISm]) have an increased risk of morbidity and mortality compared with those with normal lung function. Several gaps remain in characterizing PRISm. Research Question: What are 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, Cumulative Index to Nursing and Allied Health Literature, and Cochrane Central Register of Controlled Trials databases was conducted to include epidemiologic studies; there were 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 were extracted. Quality was assessed with the Effective Public Health Practice Project tool. Results: A total of 52 studies met the inclusion criteria, and 33 studies were 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 with high-income countries (19% vs 11%). Comorbid diabetes was a significant risk factor associated with PRISm, but the 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 = .02), cardiovascular (OR, 1.84; 95% CI, 1.31-2.58; P < .01), and respiratory (OR, 1.82; 95% CI, 1.08-3.05; P = .03) mortality. PRISm was not associated with a reduced rate of lung cancer diagnosis (P = .46). Quality assessment analysis found that 34.6% (n = 18) of studies were rated “strong,” 42.3% (n = 22) “moderate,” and 23.1% (n = 12) “weak.” Studies conducted in LMICs had lower quality ratings. Interpretation: Our findings show that individuals with PRISm have an 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 in LMICs are needed to assess unique exposures and disease trajectories relevant to these populations.