PRISm is an independent risk factor for development of COPD

<bold>Background:</bold> PRISm (Preserved Ratio Impaired Spirometry) is a phenotype for non-obstructive individuals who may be at risk for COPD. Identification of this precursor state may be crucial to establish preventive measures before manifestation of clinical disease. <bold>Aim:</bold> To evaluate PRISm as risk factor for the development of airway obstruction. <bold>Methods:</bold> The OLIN COPD Study was established in 2002-04, through re-examinations of population-based samples 993 cases with airway obstruction (FEV1/VC<0.70) and 993 controls (FEV1/VC≥0.70) were identified. The majority of these had participated in previous examinations, i.e. had a first examination during the 1980s or 90s. After excluding those with FEV1/VC<0.70 at first examination, 496 cases and 809 controls remained. Mean person-years between first- and re-examination was 10.5±4.0y. Logistic regression was performed with case as outcome and PRISm (FEV1/FVC≥0.7&FEV1<80%), former and current smoking, BMI, age and sex at first examination as covariates. <bold>Results:</bold> At first examination, the mean age was 54±11y and 56±11y in cases and controls, and the prevalence of PRISm was 33.9% and 13.6% (p<0.001), respectively. Current smoking was more common in cases (43.5%) vs. controls (18.2%), while former smoking was similar (30.6 vs. 34.5%). Annual FEV1 decline was 47±28ml vs. 32±26ml. There was no association between PRISm and smoking habits. Airway obstruction was associated with PRISm (OR 3.5 (95%CI 2.6-4.7)) and current smoking (OR 4.3 (95%CI 3.1-5.9)) after adjustment. <bold>Conclusion:</bold> PRISm is an independent risk factor for development of COPD, of similar importance as current smoking. Identification of pre-disease conditions may provide opportunities for early interventions.