Abstract Background Predictors of declining respiratory health aside from tobacco use are poorly understood. Respiratory symptoms in individuals without chronic respiratory diseases have been identified as risk factors for declining spirometry, but the mechanism connecting respiratory symptoms and progression to frank lung disease is unknown. Medically attended respiratory illnesses (MARI) have been hypothesized to be inflection points in the trajectory of lung health, due to the possibility of accumulating lung injury. We sought to investigate the connection between respiratory symptoms and spirometry in healthy adults and future respiratory illnesses. Methods The Lung Health Cohort is a longitudinal, multi-center cohort study of young adults (age 25-35 years) in the United States. Exclusion criteria include a medical history of cancer, cardiovascular disease, and chronic lung disease. Study procedures include baseline chest imaging, spirometry, biospecimen collection, and questionnaire assessments. Participants were followed with survey assessments of health events. Interval censoring accelerated failure time models a were employed to determine the relationship between time to first MARI and baseline respiratory assessments. Results 2497 participants completed follow-up assessments over a median follow-up period of 17.1 months (inter-quartile range (IQR) 8.5-24.6). 501 participants reported at least one MARI event during the follow-up period. Median age at study enrollment was 29 years old (IQR 27-32). Participants were predominantly female (1622, 65%), white (1463, 61%), non-Hispanic (1913, 77%), and non-asthmatic (2279, 91%), with a median BMI of 25.9 (IQR 22.8 - 30.0). Median forced expiratory volume in one second (FEV1) was 101% (IQR 91% - 111%) of predicted, and median forced vital capacity was 104% (IQR 94% - 114%) of predicted. Any respiratory symptoms were reported by 1191 participants (47.8%). Phlegm production was the most common symptom reported, (213, 8.6%) followed by cough (118, 4.8%). As seen in table 1, individuals with respiratory symptoms had increased hazard rate of MARI within the follow-up period. Spirometry values were inversely associated with hazard of MARI. In a sensitivity analysis excluding participants with a history of asthma, there were no substantive changes to the results. Conclusions In a cohort of healthy young adults, respiratory symptoms were common and strongly associated with respiratory illnesses requiring medical care. Impairments in spirometry also increased hazard for subsequent respiratory illnesses. This suggests a phenotype of impaired respiratory health in young adulthood which predisposes to significant respiratory infections. Further research is needed to identify ways to treat impaired respiratory health and intercept progression to chronic respiratory disease. This abstract is funded by: American Lung Association
Bailey et al. (Fri,) studied this question.