Statistical analysis

Differences in baseline characteristics were evaluated using a chi-square test (categorical variables) or Student’s t-test (continuous variables) in age, number of HF exacerbation patients in the past year, number of COPD exacerbation patients in the past year. A time-dependent Cox proportional hazards regression model was used to evaluate the effects of β-blockers on survival outcome and hospitalization rates due to CHF exacerbation and COPD exacerbation, using the β-blocker group as the time-dependent covariate. The model was adjusted by age, sex, number of HF and COPD exacerbation patients in the past year, HF and COPD exacerbation rate in the past year, comorbidities, and co-medication. The age, comorbidities, and co-medications adjusted in the model were time-varying. All analyses were performed using the SAS statistical software (version 9.4; SAS Institute Inc., Cary, NC, USA), and a P-value <0.05 was considered statistically significant.