Risk Factors, Morbidity, and Mortality in Association With Preserved Ratio Impaired Spirometry and Restrictive Spirometric Pattern: Clinical Relevance of Preserved Ratio Impaired Spirometry and Restrictive Spirometric Pattern

Abstract

BackgroundPreserved Ratio Impaired Spirometry (PRISm) and Restrictive Spirometric Pattern (RSP) are often considered interchangeable in identifying restrictive impairment in spirometry. Research QuestionDo PRISm and RSP have different individual associations with risk factors, morbidity, and mortality? Study Design and MethodsIn a cross-sectional and longitudinal study, including 26,091 30–46-year-old Norwegian general population men, we explored the association of PRISm and RSP with smoking habits, BMI, education, respiratory symptoms, self-reported cardiopulmonary disease, and mortality after 26 years of follow-up. PRISm was defined as FEV1/FVC ≥ lower limit of normal (LLN) & FEV1<LLN, RSP as FEV1/FVC≥LLN & FVC<LLN. We compared the associations of PRISm and RSP to airflow obstruction and normal spirometry, both as mutually (PRISm-alone, RSP-alone) and non-mutually exclusive (PRISm, RSP) categories, adjusting for age, BMI, smoking, education. We also conducted sensitivity analyses using GOLD criteria to define spirometric abnormalities. ResultsThe prevalence of the mutually exclusive spirometric patterns was: normal 82.4%, obstruction 11.0%, PRISm-alone 1.4%, RSP-alone 1.7%, PRISm+RSP 3.5%. PRISm-alone subjects were frequently obese (11.2%), current or former smokers, commonly reporting cough, phlegm, wheeze, asthma, and bronchitis. RSP-alone subjects were both obese (14.6%) and underweight (2.9%), with increased breathlessness, but similar smoking habits to subjects with normal spirometry. The prevalence of heart disease was 4.6% in PRISm-alone, 2.7% in RSP-alone and 1.6% in obstruction. With normal spirometry as a reference, RSP-alone had increased all-cause (HR 1.57 (1.21–2.04 95%CI), cardiovascular (1.48 (0.88–2.48)), diabetes (6.43 (1.88–21.97)), and cancer (excl. lung) mortality (1.51 (0.95–2.42)). PRISm-alone had increased respiratory disease mortality (HR 4.00 (1.22–13.16 95%CI)). Subjects with PRISm+RSP had intermediate characteristics and the worst prognosis. Findings were overall confirmed with non-mutually exclusive categories and GOLD criteria. InterpretationPRISm and RSP are spirometric patterns with distinct risk factors, morbidity and mortality, which should be differentiated in future studies.