Objectives: It is necessary to examine weight gain and affecting factors after kidney transplant. This study was performed to examine weight gain and affecting factors in kidney transplant recipients in the first 2 years after transplant.
Materials and Methods: This descriptive cross-sectional study included 139 kidney transplant recipients who were regularly followed by 2 university hospitals in the first 2 years after transplant. Data were collected with the use of a sociodemographic and clinical features’ form and the General Self-Efficacy Scale. Weight and body mass index at 3, 6, 12, and 24 months after transplant were evaluated. Differences between weight (in kilograms) and body mass index (in kilograms divided by height in meters squared) at the first outpatient clinic visit and weight and body mass index at 24 months after transplant were calculated.
Results: The mean age of patients was 46.32 ± 12.39 years. Differences in mean weight and body mass index between the first posttransplant outpatient clinic visit and at month 24 posttransplant were 7.07 ± 7.57 and 2.6 ± 2.37, respectively. Statistically significant differences were found in weight and body mass index at 2 years posttransplant. As age increased, weight gain decreased. Differences in weight gain and body mass index were not significantly associated with sex, presence of chronic diseases, donor type, steroid dose, and self-efficacy.
Conclusions: Kidney transplant recipients in our study population had increased weight and body mass index at 2 years after transplant. Younger kidney transplant recipients had higher weight gains. Therefore, kidney transplant recipients, especially younger ones, should be closely followed in terms of weight gain after transplant.

Key words : Body mass index, Nursing, Renal transplant, Self-efficacy

Introduction

Despite recent increases in graft and patient survival in the first year after kidney transplant,^1-3 the incidences of obesity and cardiovascular disease have increased, which have negative effects on patient survival and on duration of hospital stay.^4,5 In addition, weight gain and obesity after transplant can create risks of chronic nephropathy, graft loss, surgical site infection, acute rejection, and negative effects on graft survival.^6-13

Obesity can negatively affect outcomes of renal allografts in both the short- and long-term after transplant.¹⁴ In investigations of weight gain at different intervals and over different lengths of time, posttransplant weight gain has been most frequently investigated in the first year after transplant,⁵ with only one study focusing on weight gain at 3 years posttransplant. A 1-year period is not long enough to examine weight gain. In addition, factors affecting weight gain are not clear in the literature, and there have not been any studies on the effects of health behavior-related self-efficacy on weight gain. However, it is necessary to keep weight gain-related factors under control to prevent weight gain and its negative effects on transplant outcomes. It is important that nurses assess weight gain during follow-up of posttransplant patients and examine risks of weight gain. Results of our present study could be used to guide assessment of posttransplant weight gain, examination of affecting factors, and follow-up and care of posttransplant patients.

The World Health Organization has stated that a body mass index (BMI; in kilograms divided by height in meters squared) of <18.5 is considered as underweight, 18.5 to 24.9 is considered as normal weight, 25.0 to 29.9 is considered as pre-obesity, 30.0 to 34.9 is considered as class I obesity, 35.0 to 39.9 is considered as class II obesity, and ≥40 is considered as class III obesity.¹⁵ Pantik and colleagues reported that the prevalence of weight gain and obesity in the first year after transplant is very high.⁵ Hap and colleagues noted that about two-thirds of patients gained weight.¹⁶ Several other studies have revealed that 50% to 90% of patients gained weight after kidney transplant1,¹⁷ and that 10% to 35% of the patients have weight gain of 5 to 10 kg in the first year posttransplant.^3,5,16,18,19

Posttransplant weight gain can be affected by individual, environmental, and clinical factors.¹⁸ Immunosuppressive treatment can also play a role.³ The risk of posttransplant weight gain and obesity may increase as a result of decreased physical activity, genetic factors, age, female sex, high pretransplant BMI, transplant from a living donor, high daily calorie intake, unhealthy nutrition, and increased appetite led by immunosuppressive drug use and regression in uremia.^3,17-23 There have not been any studies examining the relation between kidney transplant and self-efficacy. In the present study, we evaluated the effects of self-efficacy on posttransplant weight gain. Our aim was to examine weight gain in the first 2 years posttransplant and factors affecting weight gain in kidney transplant recipients (KTRs).

Materials and Methods

Study design
The study design was descriptive and cross-sectional.

Participants
The study included 139 kidney transplant recipients regularly followed by 2 university hospitals in the first 2 years after transplant. Data were collected between October 2019 and March 2020.

Weight gain assessment
Data on weight gain during the first 2 years after transplant were obtained from medical records of patients who had kidney transplant between 2014 and 2017 in the transplant center where the study was conducted. Kidney transplant recipients can have the lowest weight at their first visit to the outpatient clinic posttransplant. To determine differences in weight and BMI correctly, the weight and BMI at the first outpatient visit were subtracted from the weight and BMI at month 24 posttransplant. However, the day when each patient presented to the outpatient clinic differed due to differences in the length of hospital stay and time of discharge. To eliminate differences between the patients in weight and BMI in the first 2 years posttransplant with respect to time, weight and BMI at month 3 posttransplant were considered as baseline values. As a result, changes in weight and BMI at 3, 6, 12, and 24 months posttransplant were evaluated. Patients were also analyzed according to 2 groups: those gaining weight and those not gaining weight or losing weight.

Because not all blood chemistry tests were performed at each follow-up, triglyceride, high-density lipoprotein, and low-density lipoprotein levels were derived from the patients who had laboratory test results. Because hemoglobin A1C was measured in only a few patients, data on hemoglobin A1C could not be evaluated.

Questionnaires
A form to gather sociodemographic and clinical information was developed in light of the literature by the researchers to collect data on sociodemo-graphic and clinical features and changes in weight.

The General Self-Efficacy Scale was utilized to collect data on self-efficacy levels of the patients. This scale, developed by Sherer and colleagues,²⁴ has a 2-factor structure: general self-efficacy and social self-efficacy. General self-efficacy was reported to explain 26.5% of the total variance and had Cronbach α of 0.86, and social self-efficacy was reported to explain 8.5% of the variance and had Cronbach α of 0.71. Each item is scored between 1 and 5, and the total score obtained from the scale ranges from 17 to 85. Higher scores on the scale show increased self-efficacy. The validity and reliability of the scale in the Turkish population were tested by Yıldırım and Özgür,²⁵ and the number of the items decreased to 17. They found that Cronbach α for the scale was 0.79.

Data on self-efficacy were collected during face-to-face interviews with the patients when they presented to the kidney transplant outpatient clinics after transplant. Self-efficacy levels of patients were examined at approximately 2, 3, 4, and 5 years posttransplant, and significant differences in self-efficacy with respect to years elapsing after transplant (minimum to maximum [min-max] of 2-5 years) were analyzed. Our analysis showed no significant difference in the mean self-efficacy level of all patients in terms of time posttransplant (F = 0.919; P = .616). For this reason, the mean self-efficacy level of all patients was included in the analysis.

Statistical analyses

Data were analyzed with the Statistical Package for Social Sciences version 23.0. Data on descriptive characteristics are presented as numbers and percentages and means and standard deviations. The Kolmogorov-Smirnov test was utilized to analyze normality of the data. The repeated measures analysis of variance was used to determine differences in mean BMI and weight in the first 2 years posttransplant. Multiple regression analysis was performed to determine whether age, sex,donor type, steroid dose, presence of chronic diseases, and self-efficacy levels were predictive of differences in weight and BMI. The statistical significance was set at P < .05. The significance level for Bonferroni corrected t test was considered as P = .008 (P = .05/6).

Results

The mean age of the kidney transplant recipients was 46.32 ± 12.39 years. The mean score for self-efficacy was 68.55 ± 9.87 (min-max, 44-85) (Table 1). The distributions of weight and BMI of the recipients at 3, 6, 12, and 24 months posttransplant are illustrated in Figure 1. Mean weight gain was 11.98 ± 12.30 kg (min-max, -24.01 to 64.90 kg). Recipients were divided into groups according to the World Health Organization BMI classification. At the first outpatient visit, 16 KTRs (11.5%) were underweight, 70 KTRs (50.4%) had normal weight, 46 KTRs (33.1%) were pre-obese, and 7 KTRs (5.0%) had class I obesity. At 24 months posttransplant, 5 KTRs (3.6%) were underweight, 50 KTRs (36%) had normal weight, 61 KTRs (43.9%) were pre-obese, 21 KTRs (15.1%) had class I obesity, and 2 KTRs (1.4%) had class II obesity. Among total patients, 116 (83.5%) had gained weight and 23 (16.5%) did not gain weight or lost weight. The laboratory results of recipients at 24 months posttransplant are presented in Table 2.

Figure 2 shows the distribution of weight and BMI at the first posttransplant outpatient clinic visit, the distribution of weight and BMI at 24 months posttransplant, and differences in weight and BMI. The mean difference in weight was 7.07 ± 7.57 kg, and the mean difference in BMI was 2.63 ± 2.37. There was a significant difference in weight and BMI in terms of time elapsed after kidney transplant (P < .001) (Table 3). Further analyses showed a significant difference in weight between months 3 and 6 (t test = -5.628, P < .001), between months 3 and 12 (t test = -6.516, P < .001), and between months 3 and 24 (t test = -7.032, P < .001). Further analyses also showed a significant difference in BMI between months 3 and 6 (t test = -8.879, P < .001), between months 3 and 12 (t test = -8.424, P < .001), between months 3 and 24 (t test = -9.345, P < .001), and between months 6 and 24 (t test = -3.913, P < .001).

Multiple regression analysis of factors affecting differences in weight in the first 2 years post-transplant revealed a significant model (R = 0.346, R² = 0.120, F = 2.995, Durbin-Watson [DW] = 2.534, P = .009). All the variables included in the model accounted for 12% of weight gain. Age was a significant and negative predictor of weight gain (B = -0.178, standard error = 0.052, t test = -3.419, beta = -0.292, P = .001). Individually, other variables were not significant predictors of differences in weight (P > .05). Multiple regression analysis of the factors affecting differences in BMI in the first 2 years posttransplant also revealed a significant model (R = 0.344, R² = 0.118, F distribution = 2.955, DW = 2.303, P = .010). All the variables included in the model explained 12% of the increase in BMI. Age was a significant, negative predictor of the difference in BMI (B = -0.053, standard error = 0.016, t test = -3.246, beta = -0.278, P = .001). Individually, other variables did not significantly predict the difference in BMI (P > .05) (Table 4).

The mean self-efficacy score with its standard deviation was 68.30 ± 9.88 in the patients who gained weight (n = 116) and 69.83 ± 9.99 in the patients who did not gain weight or lost weight (n = 23) without a significant difference (t test = 0.674, P = .502).

Discussion

We found that the KTRs included in our study experienced weight gain in the first 2 years posttransplant. The mean weight was 67.83 kg at posttransplant month 3 and increased to 71.74 kg at posttransplant month 24, with mean BMI increasing from 24.54 to 26.04. During the first 2 years posttransplant, KTRs gained weight at a rate of 11.98%. Compared with the first outpatient clinic visit, the rate of pre-obese recipients increased by 10.8%, the rate of class I obese recipients increased by 10.1%, and 2 recipients had class II obesity by 24 months posttransplant. There have been several studies to evaluate changes in weight and BMI of KTRs in the first 6 months, 1 year, 2 years, and 3 years posttransplant. Consistent with our present study, these studies revealed that, as time elapsed after transplant, weight and BMI increased.^16-19,26,27 Sukackiene and Miglinas reported that the BMI of their patients was 25.9, 26.1, and 26.4 before transplant, at 6 months posttransplant, and at 1 year posttransplant, respectively.²⁸ Cashion and colleagues noted that the mean weight of the recipients was 81.1 kg after transplant, which increased to 87.0 kg in the first year posttransplant.²⁹ Liese and colleagues also showed that BMI increased from the baseline value of 29.9 to 35 in the first year posttransplant.²¹ Forte and colleagues reported that the mean BMI was 24.7 before transplant and increased to 26.2 in the first year posttransplant.¹⁷ In a study from Williams-Hooker and colleagues, transplant recipients were found to have weight gain of 1.9 kg in the first posttransplant year compared with their weight before transplant.²⁷ Cashion and colleagues showed an increase in BMI of 2.1 in the first year posttransplant,¹⁹ and Forte and colleagues reported a weight gain of 7.12 ± 5.9 kg in the first year posttransplant.¹⁷ De Oliveira and colleagues showed that BMI increased from 21.8 at 1 month post-transplant to 24.3 at 3 years posttransplant, with rate of weight gain of 9.1%.⁷

We found that, as age increased, weight gain decreased. Although one study found no effect of age on weight gain,³⁰ most evidence in the literature is consistent with our present study. Gill and colleagues³¹ also reported that, as age increased, the mean BMI dropped. In a study from Knight and colleagues,³² women younger than 40 years had a higher weight gain in the first posttransplant year. Arshad and colleagues¹⁸ revealed that young recipients had a higher increase in BMI at 6 months posttransplant. Other studies have also shown an inverse relation between age and weight gain in transplant recipients.^7,29 With increased age, the number and size of muscle fibers decrease. It seems that, as age increases, weight loss occurs due to a decrease in muscle mass. Although BMI can suggest the amount of fat in the body, it does not provide objective data on muscle mass. For this reason, assessing BMI can lead to a misevaluation of weight gain in older recipients.³³ In addition, in general, as age increases, so does the incidence of chronic diseases. Therefore, it is necessary that recipients should have healthier eating habits.

Among our patients, we found that sex of the recipient had no effect on the differences in weight and BMI, which is compatible with the evidence from other studies.^{18,28,29,32,34} However, many studies have shown that female sex has an effect on weight gain,^5,7,16,17,21 whereas others have revealed that male recipients had a higher weight gain.^27,35 It seems that there is not an agreement on the effects of sex on weight gain.

In our present study, donor type was also found to have no effect on the differences in weight and BMI, which is consistent with some previous findings.^18,21 Turkey has the highest rate of kidney transplants from living donors in the world, at 53.02 for every 1 million.³⁶ Among our KTRs, 67.6% had living donors. In a study performed in Italy, recipients of transplants from living donors had a higher weight gain.¹⁷ In Italy, the rate of kidney transplants from living donors is 5.6 for every 1 million.³⁶ We suggest that high rates of living donor transplants can have 2 opposing psychological effects on recipients. Some recipients may not understand the value of the transplanted kidney due to shorter wait time or lack of an obligation to register on a wait list. In contrast, other recipients may be more careful and attach more value to the transplanted kidney since they may have put a loved one at risk when they received their organ. Qualitative studies are needed to gain insight into the effects of transplants from living donors. However, it was striking that donor type was shown to have no effect on weight gain in our present study, performed in a country with a very high rate of transplants from living donors.

We also found no effect of steroid dose on differences in weight and BMI. In studies that showed an effect of steroids on weight gain, patients who received steroids were compared with those who did not receive them.^21,37 Because all patients in our present study received steroids, increases in weight and BMI were compared in terms of doses of steroids given.

Among KTRs included in our study, 61.87% had a chronic disease. Consistent with our present study, renal failure is accompanied by a chronic disease in most KTRs in all reported studies. However, the presence of a chronic disease had no effect on weight gain after transplant in our study. The high rate of recipients with a chronic disease might have affected the results of the analysis. Several studies have shown that only diabetes affects weight gain after transplant,^21,26 although another study found that diabetes and hypertension had no effect.¹⁸

High self-efficacy may have a positive effect on patient adherence to their new life after transplant and may decrease undesirable outcomes.³⁸ Therefore, it was expected at the onset of this study that KTRs with high self-efficacy would have less weight gain. However, self-efficacy of KTRs in our study had no effect on differences in weight and BMI. It may be that the mean self-efficacy scores of the recipients was high (mean = 68.55).

Limitations

Our retrospective study design may have been a limitation in terms of recording and standardization of obtained data. In addition, we did not have a recipient group not taking steroids in the present study, although steroid use is an important factor in weight gain. In addition, stress, eating and endocrine disorders, and depression, which affect weight gain, were not routinely screened before and after transplant in the centers where the present study was conducted and thus could not be evaluated. In addition, the study sample included the recipients with 2- to 5-year time elapsed since transplant. Data on weight and other variables in the second year posttransplant were obtained from patient records, and these data were standardized with respect to time elapsed posttransplant. However, the mean self-efficacy was based on data obtained from not only the recipients with 2-year time elapsed since transplant but also those with 2- to 5-year time elapsed since transplant. In general, self-efficacy is not routinely assessed in transplant clinics. Therefore, data on self-efficacy displayed differences in terms of time elapsed since transplant. This can be considered as a limitation, although self-efficacy levels of KTRs were analyzed with regard to time elapsed posttransplant and found to have no effect.

Conclusions

In our examination of weight gain in the first 2 years posttransplant and the affecting factors, our KTRs experienced weight gain in the first 2 years after transplant. Younger age was found to affect weight gain. Recipient sex and the presence of a chronic disease were not found to affect weight gain. However, there is no clear evidence about this issue in the literature. Therefore, the effects of sex and chronic diseases should be rigorously examined in further studies. Turkey has the highest rate of transplants from living donors in the world. Therefore, the finding that donor type did not affect weight gain was striking. Our present study, which is the first to evaluate the effects of self-efficacy on weight gain in KTRs, showed that self-efficacy did not affect weight gain. Further studies are needed to reevaluate and elucidate the effects of self-efficacy. In addition, prospective studies could be designed to perform in-depth examinations of the factors affecting weight gain in KTRs.

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