Of the 1,500 patients selected to participate in the study and were contacted, 284 neither went to the center nor responded to the researchers' calls; Forty-eight patients had a history of substance use or were taking it; Fifteen had a history of hospitalization in a psychiatric hospital, reported in psychiatric hospitals or had traumatic brain injury; Thirty-three people answered the questionnaires incompletely or without accuracy. Finally, 1120 people entered the results analysis process.
Essential characteristics of the study population
Five hundred sixty patients with PDN participated in this study. The mean age of the subjects was 53.6± 12.6 years, of which more than half were male (342 patients, 61.1% of them) and married (90.9%). Also, the mean duration of their diabetes was 13.3± 3.4 [Table 1].
Table 1: Demographic information of participants
Variables
|
Status
|
Free count (%)
|
Gender
|
Male
|
342(61.1)
|
|
Female
|
218(38.9)
|
Marital status
|
Married
|
483(86.3)
|
|
Single
|
9(1.6)
|
|
Other Statuses
|
68(12.1)
|
Education Level
|
Under Diploma
|
389(69.5)
|
|
Diploma
|
158(28.2)
|
|
University
|
13(2.3)
|
Insulin Treatment
|
Yes
|
399(71.3)
|
|
No
|
161(28.7)
|
All of the patients were residents of Isfahan, Iran, and were Persian‑native speakers. The mean and standard deviation of the variables are reported in Table 2. Results from an independent t‑test showed that no significant difference was observed between the mean scores of Qol, pain severity, pain acceptance, depression, pain catastrophizing, and sleep disturbance in two groups of males and females (P>0.05).
Table 2: Descriptive statics of research variables
Variable
|
|
Mean ± SD
|
|
P value
|
|
Total
|
Male
|
Female
|
|
Depression
|
18.61±8.5
|
18.1±8.5
|
19.3±8.4
|
0.1
|
Anxiety
|
20.9±9.5
|
20.7±9.6
|
21.2±9.2
|
0.5
|
Quality of Life
|
69.6±21.4
|
69.5±21.9
|
69.5±20.7
|
0.9
|
Pain Severity
|
6.1±2
|
6.1±2.1
|
6.1±1.9
|
0.7
|
Pain Acceptance
|
39.1±19.07
|
38.8±18.5
|
39.6±19.8
|
0.6
|
pain Catastrophizing
|
27.3±12
|
27.4±11.8
|
27.1±12.2
|
0.7
|
Sleep Disturbance
|
11.1±4.6
|
11.3±4.05
|
11.2±4.5
|
0.5
|
Correlational matrix among variables
Pearson’s correlation (univariate correlations) between Ql, pain severity, anxiety, depression, pain acceptance, pain catastrophizing, and sleep disturbance are presented in Table 3.
According to the table.3, Qol increases with increasing pain acceptance. There is also an inverse relationship between anxiety, depression, pain catastrophizing, pain severity, sleep disturbance and Qol. Interactions between all of the variables with each other are significant, except for the correlation between pain severity and pain acceptance. Depression has the strongest negative correlation (r = −0.484) with Qol. Also, Pain severity has the weakest negative correlation (r = −0.32) with Qol.
Table 3: Correlation matrix among variables
Variables
|
Qol
|
Pain Severity
|
Anxiety
|
Depression
|
Pain Acceptance
|
Pain Catastrophizing
|
Qol
|
1
|
|
|
|
|
|
Pain Severity
|
-0.321**
|
1
|
|
|
|
|
Anxiety
|
-0.352**
|
0.135**
|
1
|
|
|
|
Depression
|
-0.484**
|
0.154**
|
0.273**
|
1
|
|
|
Pain Acceptance
|
0.409**
|
-0.104*
|
-0.3**
|
-0.289**
|
1
|
|
Pain Catastrophizing
|
-0.426**
|
0.271**
|
0.252**
|
0.273**
|
-0.295**
|
1
|
Sleep Disturbance
|
-0.367**
|
0.154**
|
0.338**
|
0.275**
|
-0.356**
|
0.271**
|
**Significant at level P<0.01, *Significant at level P<0.05
Normality and homoscedasticity of the error distribution were examined before operating the regression. The Kolmogorov–Smirnov analysis determined the normality of distribution of the variable scores. The results showed that the variables had a normal distribution. Homoscedasticity was examined using the scatter plot. In the current data, the residuals and the variance of the residuals were the same for all predicted variables. Multiple outliers were evaluated by Mahalanobis distance. None of the distances were bigger than or equal to Chi‑square, so there were no multiple outliers among the data.
Regression analysis
A step‑by‑step multiple regression analysis was conducted to predict life quality (criterion variable) based on pain severity, pain catastrophizing, pain acceptance, depression, anxiety, and sleep disturbance (predictive variables). Six models were implemented in which the sixth one demonstrated the highest R square.
According to Table 4, a significant regression equation was found: (F (10, 1110) = 74.1, P < 0.001) with an R2 = 0.42, which confirmed that the model adequately fits the data. Overall, the results showed that all independent variables significantly predicted quality of life (P < 0.05).
Table 4. Analysis of variance of model (Anova a)
|
Model
|
Sum of Squares
|
df
|
Mean Square
|
F
|
Sig.
|
1
|
Regression
|
218691.775
|
11
|
19881.070
|
74.108
|
.000
|
Residual
|
297245.936
|
1108
|
268.273
|
|
|
Total
|
515937.711
|
1119
|
|
|
|
a. Dependent Variable: quality of life
|
b. Predictors: (Constant), Insulin treatment, pain catastrophizing, age, education, sex, diabetes duration, sleep, pain acceptance, anxiety, pain severity and depression
|
|
Table 5 assesses the regression analysis of variables regarding QOL. Based on the R square measure, the current model explained approximately 42% of the variance. This model takes the form of a statistical equation.
Ypred = a + b1 *1 + b2 *2 + b3 *3 + b4 *4+b5*5+b6*6
Ypred = 110.8 - 0.71 * Depression - 0.353 * Pain catastrophizing + 0.207 * Pain acceptance–
1.67 *Pain Severity – 0.549 * sleep disturbance – 0.219 * Anxiety.
Table 5. Coefficients a of regression model
|
Model
|
Unstandardized Coefficients
|
Standardized Coefficients
|
t
|
Sig.
|
B
|
Std. Error
|
Beta
|
1
|
(Constant)
|
110.878
|
4.769
|
|
23.250
|
.000
|
Pain Severity
|
-1.671
|
.257
|
-.157
|
-6.509
|
.000
|
Pain Catastrophizing
|
-.353
|
.045
|
-.197
|
-7.773
|
.000
|
Pain Acceptance
|
.207
|
.029
|
.184
|
7.143
|
.000
|
Depression
|
-.710
|
.064
|
-.283
|
-11.016
|
.000
|
Anxiety
|
-.219
|
.058
|
-.097
|
-3.788
|
.000
|
Sleep Disturbance
|
-.549
|
.120
|
-.118
|
-4.555
|
.000
|
a. Dependent Variable: quality of life
|
Psychological Symptoms Prevalence
With a cut-off point of 14, the prevalence of depressive symptoms in this population was 63.2%. Scores are distributed in the Spectrum of Depression, which are reported in Table 6.
Table.6 Spectrum of depression in the study population
Depression category
|
Range
|
No. of Patients
|
Percentage (%)
|
Non depression
|
0-13
|
412
|
36.8
|
Mild depression
|
14-19
|
186
|
16.6
|
Moderate depression
|
10-28
|
328
|
29.3
|
Severe depression
|
29-63
|
194
|
17.3
|
As stated in the method section, the cut-off point for clinically significant anxiety on the BAI is 16. The prevalence of anxiety in patients with PDN is 62.1%. Scores are distributed in the Spectrum of anxiety, which are reported in Table 7.
Table7. Spectrum of anxiety in the study population
Anxiety category
|
Range
|
No. of Patients
|
Percentage (%)
|
Nothing anxiety
|
0-16
|
204
|
18.2
|
Mild anxiety
|
17-35
|
327
|
32.8
|
Moderate and severe anxiety
|
36-63
|
392
|
35.4
|
Also, regarding the comorbidity between depression and anxiety, 47% of patients with PDN have the comorbidity symptoms of depression and anxiety. Regarding sleep problems, the cut-off point for sleep problems is 5. Therefore, according to data, the prevalence of sleep problems in the sample is 85.5%. That is, 85% of people have significant problems related to sleep needing to follow.