Demographic characteristics of the participants
There were 320 patients with SHPT in this study: 172 (53.8%) were males, and 148 (46.2%) were females. 295(92.19%) had different degrees of forgetfulness,302(94.38%) had varying degrees of fatigue.The age of the patients ranged from 20 to 70 years. The years of renal failure ranged from 2 to 30, and the average was 10.71±4.64 years. The years of SHPT ranged from 1 to 9, and the average was 3.07±2.13 years.
Descriptive statistics
In this study,the measurement data showed a normal distribution,so it was expressed as `x±s.The QOL score ranged from 25 to 68, with an average of 41.76±8.15. The scores for bone pain and skin pruritus ranged from 1 to 10, with averages of 5.08±2.65 and 3.58±3.19, respectively. The years of bone pain ranged from 0 to 10, and the average was 2.30±1.95. The years of skin pruritus ranged from 0 to 8, and the average was 2.13±2.05. The SDS score ranged from 20 to 65, and the average was 46.04±8.98. The preoperative PTH ranged from 588 to 2934 pg/ml, and the average was 1729.15±376.20 pg/ml. The serum calcium ranged from 1.95 to 2.93 mmol/L, and the average was 2.43±0.19 mmol/L. The serum phosphorus ranged from 1.30 to 3.59 mmol/L, and the average was 2.38±0.52 mmol/L. The comparative results of each scale for SHPT patients with different demographic characteristics are shown in Table 1.
Table 1 Descriptive statistics (N=320)
Variable
|
QOL
|
|
Bone Pain
|
|
Skin Pruritus
|
|
SDS
|
t/F
|
P
|
|
t/F
|
P
|
|
t/F
|
P
|
|
t/F
|
P
|
Gender
|
2.066
|
0.040
|
|
-3.313
|
0.001
|
|
-3.300
|
0.001
|
|
-3.156
|
0.002
|
Age
|
1.635
|
0.181
|
|
2.325
|
0.075
|
|
0.428
|
0.733
|
|
2.524
|
0.058
|
Marital status
|
5.783
|
0.001
|
|
5.407
|
0.001
|
|
5.786
|
0.001
|
|
0.309
|
0.819
|
Occupation
|
2.339
|
0.042
|
|
4.708
|
0.000
|
|
4.974
|
0.000
|
|
10.076
|
0.000
|
Education
|
0.688
|
0.601
|
|
2.589
|
0.037
|
|
2.807
|
0.026
|
|
2.949
|
0.020
|
Income
|
2.185
|
0.090
|
|
1.453
|
0.228
|
|
2.153
|
0.093
|
|
5.659
|
0.001
|
Residential area
|
0.207
|
0.892
|
|
0.337
|
0.798
|
|
0.463
|
0.708
|
|
0.955
|
0.414
|
Insurance
|
1.866
|
0.116
|
|
0.617
|
0.651
|
|
1.428
|
0.225
|
|
2.884
|
0.023
|
Preliminary correlation analyses
First,the correlation analysis of renal replacement therapy (RRT) type,renal failure time,dialysis vintage,duration of SHPT and QOL,bone pain,skin pruritus,SDS showed that renal failure time was significantly (P<0.01) negatively correlated with QOL (r=-0.232) and positively correlated with skin pruritus (r=0.142) and SDS (r=0.149),other variables were not relevant.The Pearson correlation analysis of QOL, bone pain, skin pruritus and SDS is presented in Table 2. The results showed that QOL was significantly (P<0.01) and negatively correlated with bone pain (r=-0.509), skin pruritus (r=-0.517) and SDS (r=-0.465). Bone pain was significantly (P<0.01) and positively correlated with skin pruritus (r=0.568) and SDS (r=0.450). Skin pruritus was significantly (P<0.01) and positively correlated with SDS (r=0.426).
Table 2 Correlations between the main variables (N=320)
Variable
|
QOL
|
Bone pain
|
Skin pruritus
|
SDS
|
QOL
|
1
|
|
|
|
Bone pain
|
-0.509**
|
1
|
|
|
Skin pruritus
|
-0.517**
|
0.568**
|
1
|
|
SDS
|
-0.465**
|
0.450**
|
0.426**
|
1
|
Note:**P<0.01
Testing for the mediation effect
The variable was normalized first, and three regression equations were established according to the purpose of this study. Equation 1: depression as the dependent variable and bone pain or skin pruritus as the independent variable; Equation 2: QOL as the dependent variable, with SDS and bone pain or skin pruritus as the independent variable; and Equation 3: SDS as the dependent variable, with QOL and bone pain or skin pruritus as the independent variable. The results showed that bone pain and skin pruritus could significantly predict depression (β=0.485/0.375, P=0.000) and that bone pain and skin pruritus could significantly predict QOL (β=-0.407/-0.337, P=0.000). When bone pain or skin pruritus and QOL predicted SDS at the same time, the predictions were significant (β=0.310/0.223, P=0.000; β=-0.429/-0.450, P=0.000). This indicated that the direct or indirect effects of bone pain or skin pruritus on SDS were significant; that is, QOL plays an intermediary role between bone pain or skin pruritus and SDS. The results are shown in Tables 3 and 4.
Table 3 The moderating effects of QOL (Part 1)
Equation
|
Dependent
variable
|
Independent variable
|
β
|
SE
|
t
|
P
|
Equation 1
|
SDS
|
Bone pain
|
0.485
|
0.054
|
8.984
|
0.000
|
Equation 2
|
QOL
|
Bone pain
|
-0.407
|
0.039
|
-10.548
|
0.000
|
Equation 3
|
SDS
|
Bone pain
|
0.310
|
0.060
|
5.190
|
0.000
|
|
|
QOL
|
-0.429
|
0.075
|
-5.740
|
0.000
|
Table 4 The moderating effects of QOL (Part 2)
Equation
|
Dependent
variable
|
Independent variable
|
β
|
SE
|
t
|
P
|
Equation 1
|
SDS
|
Skin pruritus
|
0.375
|
0.045
|
8.404
|
0.000
|
Equation 2
|
QOL
|
Skin pruritus
|
-0.337
|
0.031
|
-10.757
|
0.000
|
Equation 3
|
SDS
|
Skin pruritus
|
0.223
|
0.050
|
4.510
|
0.000
|
|
|
QOL
|
-0.450
|
0.076
|
-5.929
|
0.000
|
Verification of the mediating effect
On the basis of multivariate regression analysis, the bootstrap method was used to further test the intermediary effect of QOL. To test the intermediary effect, we needed to establish a structural equation model, and we used AMOS 23.0 to test it. The specific path analysis diagram is shown in Figures 1 and 2.
The structural equation model fit results showed that CMIN/DF=2.437/1.202 (<3); AGFI=0.928/0.965, GFI=0.960/0.980, TLI=0.961/0.994, IFI=0.973/0.996, and CFI=0.973/0.996 (>0.9); and SRMR=0.042/0.026 and RMSEA=0.067/0.025 (<0.08), indicating that the model fit well. The results showed that the confidence intervals for both the direct and indirect effects of bone pain and skin pruritus on SDS did not reach 0. The mediating effect model of QOL was established, and the mediating effect was 0.212/0.275, accounting for 48.62%/45.08% of the total effect. See Tables 5 and 6 for details.
Table 5 Results for total, indirect and direct effects of bone pain on SDS with QOL as a mediator
|
SE
|
Bias-Corrected
|
Percentile
|
95%CI
|
95%CI
|
Lower
|
Upper
|
Lower
|
Upper
|
total effect
|
Bone pain—SDS
|
0.436
|
0.279
|
0.585
|
0.276
|
0.581
|
indirect effect
|
Bone pain—QOL—SDS
|
0.212
|
0.101
|
0.371
|
0.069
|
0.336
|
direct effect
|
Bone pain—SDS
|
0.224
|
0.053
|
0.43
|
0.061
|
0.438
|
Table 6 Results for total, indirect and direct effects of skin pruritus on SDS with QOL as a mediator
|
SE
|
Bias-Corrected
|
Percentile
|
95%CI
|
95%CI
|
Lower
|
Upper
|
Lower
|
Upper
|
total effect
|
Skin pruritus—SDS
|
0.61
|
0.435
|
0.795
|
0.433
|
0.792
|
indirect effect
|
Skin pruritus—QOL—SDS
|
0.275
|
0.188
|
0.378
|
0.183
|
0.374
|
direct effect
|
Skin pruritus—SDS
|
0.335
|
0.179
|
0.493
|
0.179
|
0.492
|