Data analysis
We first used descriptive analysis to describe the characteristics of the study sample. Then multiple logistic regressions were used to examine the associations of PA with outpatient visit, inpatient admission, outpatient visit in PHC facilities and inpatient admission inside counties. Individual and county characteristics were controlled. Lastly, we compared PA estimates between 2013 and 2018 using a fully interactive model to examine changes in PA impact, and the Chow test was used to compare the differences16, 17. Two-sided p-values less than 0.05 were considered statistically significant. Stata 15.0 (Stata Corp LP, College Station, TX, USA) was used to perform all analyzes.

Results

The characteristics of the study sample are presented in Table 1. Overall, the majority of rural patients with chronic diseases were female, aged 60 years or older, married and had a low education level of primary school or below, consistent with the 2013 and 2018 waves. In 2018, 37.9% of middle-aged 35-59-year-olds in rural areas had chronic diseases, which was greater than 28.5% in 2013. The majority of rural patients with chronic diseases were covered by health insurance. We also presented the characteristics of all rural residents in two waves of survey (Supplementary file, Table S1).
Table 1. Characteristics of the study sample