SELF-ADMINISTERED EXERCISE AND BONE MINERAL DENSITY IN PATIENTS WITH CHRONIC KIDNEY DISEASE: A SUBSTUDY OF RENEXC-A RANDOMIZED CONTROLLED TRIAL

Abstract BACKGROUND AND AIMS The aim of the study was to evaluate the effects of 12 months self-administered exercise training on bone mineral density (BMD) in non-dialysis-dependent patients with chronic kidney disease stages 3–5. METHOD In this single-centre, randomized controlled trial, 151 patients were allotted 60 minutes of endurance training in combination with 90 minutes of either balance or strength training. The exercise was prescribed and monitored by a physiotherapist and performed at home or a gym. Total body-, hip- and lumbar BMD (g/m2), T-score and Z-score were measured at baseline (T0) and after 12 months (T12) using dual-energy X-ray absorptiometry (DEXA). A total of 112 patients completed the study. Of these, five patients were excluded from analysis because they missed either the T0 or T12 DEXA evaluation. To evaluate between-group changes after the study period delta BMD, delta T-score and delta Z-score values (T12 value–T0 value) were calculated. These results were also used to define progressors and non-progressors. Statistical analyses were performed using SPSS for Windows 24. Statistical significance was assessed using Student's t-test, paired-sample t-test, Mann–Whitney or Wilcoxon matched-pairs signed-rank tests depending on normality of data distribution. The two-tailed chi-squared test was used to compare categorical variables. Values are given as mean ± SD or median (min-max). A P-value < 0.05 was accepted as the level of significance. RESULTS A total of 107 patients [69 men, 38 women; age 66 ± 13.5 years, measured glomerular filtration rate (GFR) 22 ± 8 mL/min/1.73 m2] were analysed. There were 50 patients (34 men, 16 women) in the strength group and 57 (35 men, 22 women) in the balance group. After 12 months of training the whole group showed a statistically significant decrease in hip BMD [0.886 (0.479–1.922) T0 versus 0.873 (0.521–2.045) T12, P = 0.002], hip T score [−1.177 ± 1.419 T0 versus − 1.4 (−4.0 to 6.6) T12, P = 0.049] and total body BMD (1.156 ± 0.508 T0 versus 1.149 ± 0.164 T12, P = 0.032). When data were analysed separately within each group, the strength group showed a decrease in total body BMD (1.152 ± 0.151 T0 versus 1.141 ± 0.153 T12, P = 0.001). Changes in total body T-score and Z-score did not reach the level of significance (T-score − 0.392 ± 1.56 T0 versus − 0.484 ± 1.56 T12, P = 0.138; Z-score 0.07 ± 1.19 T0 versus − 0.012 ± 1.21 T12, P = 0.052). The balance group showed a statistically significant increase after 12 months training in total body T-score (−0.312 ± 1.659 T0 and − 0.196 ± 1.707 T12, P = 0.035) and total body Z-score [0.05 ± 1.626 T0 and 0.4 (−5.1 to 6.8) T12, P = 0.003] but not in total body BMD [1.16 ± 0.151 T0 versus 1.123 (0.668 to 1.818) T12, P = 0.135]. Delta total body T-score was negative in the strength group [−0.10 (−1.0 to 2.1) and unchanged in the balance group 0.00 (−0.60 to 1.00), showing a significant between-group difference (P = 0.005)]. Delta total body Z-score was negative in the strength group (−0.092 ± 0.430) and positive in the balance group (0.1158 ± 0.403) showing a significant between-group difference (P = 0.001). Moreover, the proportion of progressors was higher in the strength group as shown by the delta total body T-score (60%) strength versus (40%) balance group (P = 0.006) and delta total body Z-score (61%) and (40%) respectively (P = 0.029). CONCLUSION Balance—in combination with endurance training seemed to be superior to strength—in combination with endurance training in preserving and even improving bone health. The 12 months of balance training resulted in an increase in total body T-score and Z-score, respectively. The strength group showed a decrease in total body BMD after 12 months of training. Moreover, when comparing the delta values there were significant between-group effects with the balance group showing an unchanged T-score in comparison with the strength group's decreased T-score and a positive Z score in comparison with the strength group's negative value. Finally, a greater proportion of participants in the strength group were classified as progressors with a deterioration of bone health.