Figure 3
Associations between post-bronchodilator forced vital capacity/total lung capacity (FVC/TLCCT) quartiles at enrollment with prospective exacerbations and severe exacerbations in smokers with Preserved Ratio Impaired Spirometry (PRISm; n = 967). For exacerbation analysis, data for 967 subjects with PRISm at enrollment were available. Zero-inflated negative binomial regression models with post-bronchodilator FVC/TLCCT as independent variable (exposure) and total exacerbations and severe exacerbations as the dependent variables (outcome) were performed. All regression models included the following co-variates: age, sex, race, body mass index, smoking status at the enrollment, smoking pack-years, history of asthma and congestive heart failure, and chronic bronchitis in the count negative binomial regression and an intercept-only model in the zero component. Follow-up time was included as an offset in the models. FVC/TLCCT quartile is plotted on the x-axis while the IRR (and 95% CI) for each category is plotted on the y-axis. IRR = incidence rate ratio, FVC/TLCCT = forced vital capacity/total lung capacity.
