Study design
A single-center cross-sectional study was carried out from October 2018 to April 2019.
Sample and setting
Patients were recruited from the nephrology department in Shanghai, China. The sample size was determined based on the number of variables. Taking into account 10 variables in this study, a sample size should be 5-10 times of the variables according to Kendall’s calculation principle, and considering the invalid questionnaire, the sample size was therefore set at 120 (10*10*1.2=120), plus the samples (n=17) included in the pre-experiment, the final sample size for this study was 137.
Data collection
Three researchers (WHZ, JL and HW) approached potential inpatients of nephrology. The inclusion criteria were as follows: (1) patients were diagnosed as CKD met the criteria of the National Kidney Foundation [14]; (2) patients who did not participate in other exercise-related clinical trials, and (3) patients who were 18 or older and able to communicate in both oral and writing the Chinese language, had no mental and conscious disorders and volunteered to participate in this study. Patients who received dialysis (ex. peritoneal dialysis, hemodialysis) or complicated with severe organic diseases were excluded.
Variable instrument
Self-administered questionnaire
For socio-demographic, age, gender, body mass index (BMI), employment status, average monthly income, education level, stage of the disease, time of diagnosis, and daily physical activity were surveyed by a self-administered questionnaire.
Leicester Uremic Symptom Score (LUSS)
LUSS was used to measure symptom burden. The LUSS has proved useful and sensitive to change in CKD patients as an outcome measure to assess symptoms in cross-sectional studies [15], which assesses the frequency (how often a patient experienced a symptom) and intrusiveness (how much a symptom affects patient’s life) of 11 symptoms, including itching, sleep disturbance, loss of appetite, excessive tiredness, pain in bones/joints, poor concentration/mental alertness, impotence/lack of sex drive, loss of muscle strength/power, shortness of breath, muscle spasm/stiffness and restless legs. The frequency was assessed using “never”, “1-2 times a week”, “several times a week” and “every day”. Intrusiveness was assessed including “not applicable”, “not at all intrusive”, “slightly intrusive”, “quite intrusive”, “very intrusive’ and “extremely intrusive”, scored from 0 to 5 [15].
Exercise Self-Efficacy Scale (ESES)
ESES was used to measured exercise self-efficacy, which was developed by Bandura, with a Cronbach`s alpha coefficient of 0.96 [16]. The scale contains 18 items, categorized into three dimensions including competing demands, internal feelings, and situation/interpersonal. Each of these targets for situations that may affect the patients engage in physical activity. For each item, individuals describe their confidence to finish the behavior on a 100-point scale comprised of 10-point increments. 0 means “not at all unconfident", 50 indicates “moderately confident”, 100 indicates “highly confident”. The overall score for the ESES was calculated by adding all of the item scores and dividing by the number of items [16].
Ethical approval
The study was approved by the Ethics Committee of Longhua Hospital. Before signing the consent form, each participant received an oral explanation of the study procedures, and the right to withdraw at any time. Using identification numbers instead of real names for the data record protected participants’ confidentiality.
Statistical analysis
Data were analyzed using the Statistical Package for Social Sciences, version 21.0 (SPSS Inc., Chicago, IL, USA). Results were reported as frequencies and percentages or mean ± SDs or as median (lower quartile, upper quartile) based on normality test, which was analyzed using the Kolmogorov-Smirnov test. The Mann-Whitney U test or Kruskal-Wallis test was used to analysis
non-normal data according to the number of groups. The Spearman correlation coefficient was used to assess the correlation between the ESES scores and symptom burden values. Multiple linear regression was carried out to identify factors that were significantly associated with ESES. The independent factors were including socio-demographic, and symptom burden. A dummy coding of 0 and 1 were used to enter the categorical variable into the regression model. Variables with a p < 0.05 in univariate analysis were entered into the regression model. Statistical significance was set at a p < 0.05.
Table 1
Socio-demographic and clinical characteristics of the study sample (n = 137)
Variables | Frequency (%) | Variables | Frequency (%) |
Age (Year) | | Stage of disease | |
< 65 | 94 (68.6%) | CKD stage 1 | 30 (21.9%) |
≥ 65 | 43 (31.4%) | CKD stage 2 | 34 (24.8%) |
Gender | | CKD stage 3 | 32 (23.4%) |
Male | 78 (56.9%) | CKD stage 4 | 20 (14.6%) |
Female | 59 (43.1%) | CKD stage 5 | 21 (15.3%) |
BMI (kg/m2) | | Time of diagnosis (year) | |
< 18.5 | 6 (4.4%) | < 1 | 33 (24.1%) |
18.5 ~ 24 | 66 (48.2%) | 1 ~ 3 | 19 (13.9%) |
> 24 | 65 (47.4%) | > 3 | 85 (62.0%) |
Employment status | | Daily physical activity (min) (min) | |
Employed | 41 (29.9%) | < 30 | 60 (43.8%) |
Unemployed | 96 (70.1%) | 30 ~ 60 | 50 (36.5%) |
Average monthly income | | > 60 | 27 (19.7%) |
Poor | 12 (8.8%) | | |
Moderate | 88 (64.2%) | | |
Good | 37 (27.0%) | | |
Education level | | | |
Primary school and below | 21 (15.3%) | | |
Junior middle school | 46 (33.6%) | | |
Senior school or technical secondary school | 31 (22.6%) | | |
College and above | 39 (28.5%) | | |
Abbreviations: CKD chronic kidney disease; BMI body mass index; |
Table 2
ESES total score by socio-demographic and clinical variables (n = 137)
Variables | ESES index score | P-value |
Mean ± SD | Median [interquartile range] |
Age (Year) | | | |
< 65 | 50.94 ± 19.07 | 51.67[34.44, 69.72] | 0.040a |
≥ 65 | 44.28 ± 16.18 | 42.78[30.56, 54.44] |
Gender | | | |
Male | 51.96 ± 18.96 | 50.84[34.44, 67.92] | 0.030a |
Female | 44.74 ± 16.97 | 42.78[30.56, 60.56] |
BMI (kg/m2) | | | |
Underweight (< 18.5) | 32.31 ± 15.99 | 29.17[23.89, 41.11] | 0.048b |
Normal (18.5 ~ 24) | 50.93 ± 17.67 | 50.56[33.75, 66.95] |
Overweight (> 24) | 48.27 ± 18.79 | 46.11[34.17, 62.78] |
Employment status | | | |
Employed | 47.93 ± 18.07 | 49.44[30.56, 63.06] | 0.769a |
Unemployed | 49.24 ± 18.64 | 48.89[33.47, 66.11] |
Average monthly income | | | |
Poor | 45.70 ± 16.20 | 46.39[30.97, 57.64] | 0.005b |
Moderate | 45.68 ± 17.84 | 45.84[30.84, 61.11] |
Good | 57.41 ± 18.13 | 61.11[39.45, 71.95] |
Education level | | | |
Primary school and below | 47.28 ± 16.22 | 48.89[31.67, 57.50] | 0.547b |
Junior middle school | 45.71 ± 16.40 | 44.73[33.32, 57.64] |
Senior school or technical secondary school | 51.58 ± 20.40 | 51.11[33.89,63.33] |
College and above | 51.23 ± 20.08 | 53.33[30.56, 68.33] |
Stage of disease | | | |
CKD stage 1 | 55.06 ± 18.28 | 55.28[40.56, 70.56] | 0.027b |
CKD stage 2 | 53.09 ± 17.16 | 53.34[37.64, 68.06] |
CKD stage 3 | 44.77 ± 17.92 | 39.17[29.72, 62.22] |
CKD stage 4 | 46.28 ± 18.08 | 43.34[32.91, 61.81] |
CKD stage 5 | 41.77 ± 18.80 | 37.78[28.62, 51.39] |
Time of diagnosis (year) | | | |
< 1 | 47.70 ± 18.69 | 42.78[32.50, 66.67] | 0.930b |
1 ~ 3 | 48.68 ± 16.94 | 49.44[30.00, 60.11] |
> 3 | 49.33 ± 18.81 | 50.00[33.31, 64.17] |
Daily physical activity (min) | | | |
< 30 | 33.39 ± 10.86 | 33.03[25.00, 38.75] | < 0.001b |
30 ~ 60 | 57.36 ± 13.16 | 54.17[49.86, 66.67] |
> 60 | 67.46 ± 11.39 | 68.89[62.22, 72.78] |
Abbreviations: ESES Exercise Self-efficacy Scale, CKD chronic kidney disease; BMI body mass index; |
aStatistical significance of differences calculated using the Kruskal-Wallis test |
bStatistical significance of differences calculated using the Mann-Whitney U test |
Table 3
Multiple linear regression analysis of association between factors and ESES score
Variables | Unstandardised coefficients (B) | Standardised coefficients (Beta) | P-value | 95% CI for B |
Age (Year) | | | | |
< 65 | Reference | | | |
≥ 65 | 0.313 | 0.008 | 0.899 | −4.562−5.189 |
Gender | | | | |
Male | Reference | | | |
Female | −2.489 | −0.067 | 0.262 | −6.864−1.886 |
BMI (kg/m2) | | | | |
Underweight | −3.083 | −0.034 | 0.563 | −13.594−7.428 |
Normal | Reference | | | |
Overweight | −1.061 | −0.029 | 0.624 | −5.328−3.206 |
Income (month) | | | | |
Poor | −0.836 | −0.013 | 0.830 | −8.544−6.872 |
Moderate | Reference | | | |
Good | 5.449 | 0.132 | 0.036 | 0.357–10.541 |
Stage of disease | | | | |
CKD stage 1 | Reference | | | |
CKD stage 2 | −0.648 | −0.015 | 0.831 | −6.643−5.346 |
CKD stage 3 | −1.451 | −0.033 | 0.642 | −7.616−4.713 |
CKD stage 4 | 1.252 | 0.024 | 0.723 | −5.712−8.216 |
CKD stage 5 | −3.847 | −0.076 | 0.285 | −10.936−3.242 |
Daily PA (min) | | | | |
< 30 | Reference | | | |
30 ~ 60 | 22.348 | 0.586 | < 0.001 | 17.605–27.091 |
> 60 | 31.257 | 0.678 | < 0.001 | 25.413–37.101 |
LUSS | | | | |
Continuous | −0.165 | −0.058 | 0.365 | −0.524−0.194 |
Abbreviations: ESES Exercise Self-efficacy Scale, CKD chronic kidney disease; BMI, body mass index; PA physical activity; LUSS Leicester Uremic Symptom Score; CI confidence interval |