Importance of Preserved Ratio Impaired Spirometry as a Risk Factor for Development of COPD, Also in Those Who Do Not Smoke

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BACKGROUND: COPD is largely underdiagnosed. Active identification of cases is crucial to establish preventive measures before manifestation of clinical disease. The significance of different spirometric patterns preceding COPD, especially preserved ratio impaired spirometry (PRISm), has been highlighted but remains unclear. RESEARCH QUESTION: Which clinical characteristics, smoking habits, and spirometric patterns, with primary focus on PRISm findings, precede the development of airway obstruction (AO)? STUDY DESIGN AND METHODS: to VC ratio ≥ 0.70). Most of these people had participated in examinations during the 1980s or 1990s, and in total, 902 cases and 819 control participants had previous clinical data. Logistic regression was performed with case status as outcome and spirometric patterns, age, sex, smoking habits, and BMI at first examination as covariates. RESULTS: The mean (SD) person-years between first examination and inclusion in the OLIN COPD Study was 10.5 (4.0) years. At first examination, the prevalence of PRISm was higher in cases (18.6%) vs control participants (13.4%). Current smoking was more common in cases (45.1% vs 18.2%), whereas former smoking was similar (31.8% vs 34.9%). Cases reported more respiratory symptoms (78.0% vs 44.3%) than control participants. At first examination, PRISm, current smoking, and former smoking were strongly associated with becoming a case when adjusted for confounders, with adjusted OR (aOR) of 3.5, 4.1, and 1.5, respectively. When stratifying for smoking habits, aORs for PRISm in those with current smoking, former smoking, and nonsmoking status were 2.9, 3.8 and 3.7, respectively. INTERPRETATION: In this study, PRISm was associated with transition into AO corresponding to COPD within 1 decade, independent of smoking habits and with similar strength of association among those who have never smoked, who formerly smoked, and who currently smoke.