Patient Characteristics and Comorbidities
All 3073 incident CAPD patients from five dialysis centers were included in the present study. All variables with less than 5% missing data were imputed before the data analysis, and there was no missing data for outcomes. Of 3073 with a median age of 49.0 (IQR 39.0-61.0), 1780 (57.9%) were men, 1987 (64.6%) had HTN, 431 (14.1%) had pre-existing CVD, and 567 (18.4%) had diabetes mellitus. All patients were divided into four group: HTN plus CVD group (n=370, 12.0%), CVD group (n=60, 2.0%), HTN (52.6%) group, and the control group (n=1027, 33.4%, Table 1). Compared to the control group, HTN plus CVD group tended to be elderly, with higher body mass index, systolic BP, hemoglobin, and cholesterol, but lower diastolic BP, as well as more likely to be current smoking, diabetes mellitus, hyperlipidemia, taking calcium channel blockers, beta blockers, diuretics, ACEI/ARBs, aspirin, and statins.
Related Factors and Co-existence of HTN plus pre-existing CVD, Pre-existing CVD, and HTN
We analyzed baseline factors associated with the co-existence of HTN and CVD, pre-existing CVD, and HTN versus the control group using the multinomial logistic regression (Table 2). When adjusting for confounding factors, elderly age and diabetes mellitus were associated with higher risk of co-existence of HTN and CVD, pre-existing CVD, and HTN versus the control group. Men was independently associated with higher risk co-existence of HTN and CVD, lower body mass index was associated with higher risk of pre-existing CVD, higher systolic BP and diastolic BP were associated with higher risk of HTN and co-existence of HTN and pre-existing CVD, lower hemoglobin was associated with higher risk of HTN, and higher cholesterol and lower low density cholesterol were associated with higher risk of co-existence of HTN and pre-existing CVD, compared with the control group. Of note, diabetes mellitus was associated with 6.22 (4.46 to 8.68)-time risk of co-existence of HTN and pre-existing CVD, followed by hyperlipidemia with 2.05 of odd ratio (1.51 to 2.78). Lower levels of low density cholesterol was associated with high risk of co-existence HTN and pre-existing CVD (odd ratio 0.98, 95% CI 0.97 to 0.99).
Observational Period and Mortality
The median observational period was 33.7 (IQR 15.7-60.9) months. During this period, 571 (18.6%, 95% CI 17.1 to 20.0%) patients died, with 286 (9.3%, 95% CI 8.2% to 10.4%) CVD deaths, 59 (1.9%, 95% CI 1.2% to 2.8%) infection deaths, 10 (0.3%, 95% CI 0.1% to 0.6%) gastrointestinal bleeding, 17 (0.6%, 95% CI 0.3 to 0.8%) tumor deaths, 101 (3.3%, 95% CI 2.7% to 3.9%) other death causes, and 89 (2.9%, 95% CI 2.3% to 3.5%) unknown death causes. In addition, 375 (12.2%, 95%CI 11.2% to 13.4%) transferring to hemodialysis, 159 (5.2%, 95% CI 4.5% to 6.0%) receiving renal transplants, 26 (0.8%, 95% CI 0.6% to 1.2%) transferring to other dialysis centers, and 106 (3.4%, 95% CI 2.8% to 4.1%) loss of follow-up. The number of all-cause mortality was 143 (38.6%, 95% CI 33.7% to 44.2% ), 15 (25.0%, 95% CI 14.6% to 36.0%), 293 (18.1%, 95% CI 16.2% to 20.1%), and 120 (11.7%, 95% CI 9.7% to 13.5%) in the HTN plus CVD, CVD, HTN, and control groups, respectively. The number of CVD mortality was 76 (20.5%, 95% CI 16.5% to 25.0% ), 7 (11.7%, 95% CI 4.8% to 21.1%), 147 (9.1%, 95% CI 7.7% to 10.6%), and 56 (5.5%, 95% CI 4.2% to 6.8%) in the HTN plus CVD, CVD, HTN, and control groups, respectively.
The incidence of all-cause mortality was 55.7/1000 patient-years in the study population, with 27.9/1000 patient-years of CVD mortality incidence (Table 3). The incidence of all-cause mortality was 131.0, 74.4, 56.1, and 32.2/1000 patient-years, and CVD mortality incidence was 69.6, 34.7, 28.2, and 15.0/1000 patient-years among the HTN plus CVD, CVD, HTN, and control groups, respectively.
Comorbidities and Mortality
Survival analysis found that the HTN plus CVD group had poorer cumulative survival (P<0.001) and CVD mortality-free survival (P=0.006) compared to the control group (Figure 1). The association between comorbidities and mortality was evaluated by the different Cox proportional hazards regression models (Table 4). When comparing to the control group, the HTN plus CVD, CVD and HTN groups had 3.98 (95% CI 3.07 to 5.17), 2.18 (95%CI 1.27 to 3.74), and 1.83 (95%CI 1.47 to 2.28)-time risk of all-cause morality, and 4.68 (95%CI 3.27 to 6.69), 2.11(95%CI 0.96 to 4.63), and 1.87 (95%CI 1.37 to 2.54)-time risk for CVD mortality compared to the control group in the model 4, respectively. Similar trends were observed among subgroups of men, women, diabetes mellitus, non-diabetes mellitus, hyperlipidemia, and non-hyperlipidemia (Figure 2). There was no significant interaction between HTN and CVD on all-cause and CVD mortality (β=0.010, P=0.973; β=0.058, P=0.892) in the study population.
Sensitivity Analysis
When performing competing risk analyses with hemodialysis or renal transplants as the competing risk factors, the HTN plus CVD, CVD, and HTN groups had 3.00 (95% CI 2.19 to 4.11), 2.03 (95%CI 1.11 to 3.73), and 1.37 (95%CI 1.07 to 1.75)-time risk of all-cause morality compared to the control group, respectively, in the Fine and Gray model 4. Similarly, when using non-CVD mortality, hemodialysis or renal transplants as the competing risk factors, compared to the control group, the HTN plus CVD, CVD, and HTN groups had 3.17 (95% CI 2.03 to 4.97), 2.01 (95%CI 0.83 to 4.89), and 1.54 (95%CI 1.08 to 2.18)-time risk of all-cause morality, respectively, in the Fine and Gray model 4.
A total of 42 (1.4%) patients aged < 18 years at the start dialysis were excluded, with 6 deaths at the end study. By the end of study, 810 (26.3%) adult patients were follow up less than 24 months, and 282 (9.2%) adult patients survived for less than 24 months. The remaining 1939 (63.1%) adult patients were follow up for at least 24 months, with 283 (14.6%, 95% CI 12.9% to 16.1%) of all-cause mortality and 135 (7.0%, 95% CI 5.8% to 8.1%) of CVD mortality. We found that when comparing to the control group, the HTN plus CVD, CVD, and HTN groups had 3.53 (95% CI 2.32 to 4.84), 1.73 (95% CI 1.01 to 2.97), and 1.46 (95% CI 1.17 to 1.81)-time risk of all-cause mortality, and 4.59 (95% CI 2.70 to 7.79), 1.93 (95% CI 0.88 to 4.28), and 1.58 (95% CI 1.15 to 2.16)-time risk of CVD mortality in the Cox regression model 4, respectively, among adult those with at least 24-month follow-up period.