Association of small airways obstruction and mortality

Background The evidence assessing the association between small airways obstruction (SAO) and risk of mortality is limited. We aim to investigate the association between SAO and all-cause mortality in the general population. Methods Participants aged 18–79 years old with qualifying spirometry and mortality data from the National Health and Nutrition Examination Survey (NHANES) 1988–1994 and 2007–2012 cycles were included in this study. SAO was defined as maximal mid-expiratory flow (MMEF) less than the lower limit of normal (LLN). Logistic regression analysis was used to assess the relationship between SAO and respiratory symptoms and comorbidities. The Cox proportional hazard ratio model was used to investigate the association between SAO and all-cause mortality. Repeated the analysis among the participants with normal spirometry. Results A total of 25263 participants (48.7% male; mean age 44 years) were include in the study. During a median follow-up time of 309 months. 5583 (22.1%) deaths occurred, Including 940 (30.8%) participants with SAO and 4643 (20.9%) participants without SAO. SAO was associated with a heightened risk of chronic cough, chronic phlegm, wheezing, shortness of breathes, congestive heart failure, asthma, chronic bronchitis, emphysema, and cancer. Compared with participants without SAO, the unadjusted HR (95% Cl) and fully-adjusted HR (95% Cl) of all-cause mortality risk were 1.59 (95% CI 1.48–1.70) and 1.42 (95% CI 1.32–1.54) for those with SAO, respectively. Among the participants with normal spirometry, these associations were similar. Conclusions Our study indicated that SAO was associated with an increased risk of chronic respiratory symptoms, comorbidities, and all-cause mortality in the general population.