Statistical analysis
Logistic regression and univariate analyses were performed to determine the predictors of PIMs in our study population. The candidate predictors included age, sex, number of comorbidities, number of prescribed medications, and classes of healthcare facilities (first-tier, second-tier or third-tier hospitals). Detailed information on the classification of three-tiered healthcare system in China is provided in the online supplementary appendix table 1. Statistical analyses were performed with the application of SPSS Version 19.0 (Statistical Product and Service Solutions) for Windows.