The ESRD incidence densities for the PP and non-PP cohorts and the ESRD crude (relative) hazard ratios (HRs) for the patients in the PP cohort compared with those in non-PP cohorts are summarized in Table 2. The overall incidence of ESRD was 23% higher in the PP cohort than in the non-PP cohort (5.26 vs. 3.10 per 1000 person–years), with an adjusted HR of 1.14 (95% confidence interval (CI) 1⁄4 1.01–1.29). The incidence rates were 5.08 and 5.53 per 1000 person–years for the male and female PP patients, respectively. The crude HRs of ESRD for the male and female PP patients were 1.21 and 1.26, respectively, compared with the male and female non-PP subjects. The highest age- specific ESRD incidence rates for patients with PP were observed in patients aged 50–64 years (7.68 per 1000 person–years), with an adjusted HR of 1.61 (95% CI1⁄41.28–2.02) compared with the non-PP cohort in the same age subgroup. The age-specific hazard ratio of ESRD in the PP cohort was greatest for patients aged p34 years, with an adjusted HR of 4.15 (95% CI 1⁄4 1.55–11.1) compared with the non-PP cohort in the same age subgroup.The increased adjusted HRs of ESRD in the PP cohort were observed in the comorbid subgroups of hypertension (adjusted HR 1⁄4 1.19; 95% CI 1⁄4 1.01–1.39) and malignancy (adjusted HR 1⁄4 2.15; 95% CI 1⁄4 1.05–4.40) compared with that of the non-PP cohort. However, the case numbers in the malignancy subgroup were small in both cohorts, and the interpretation of the increased adjusted HRs in the malignancy subgroup should be limited. In the other aspect, the decreased adjusted HR of ESRD in the PP cohort was observed in patients with COPD (adjusted HR1⁄40.71; 95% CI1⁄40.52–0.96) compared with those without COPD. In the non-CKD subgroup, the adjusted HR of ESRD was higher in patients with PP compared with those without PP (adjusted HR = 1.20; 95% CI =1.05–1.37).