Systemic inflammation in HD patients has adverse outcomes including nutritional and metabolic abnormalities with increase rate of morbidities and mortalities . The participation in aerobic exercise has been recommended by the National Kidney Foundation and Kidney Disease: Improving Global Outcomes for dialysis patients .
This study aimed to evaluate the effect of intradialytic aerobic exercise on inflammatory markers such as CRP and IL-6 in prevalent hemodialysis patients. In this work, at baseline, there was no difference between patients in exercise group (EG) and non-exercise group (NEG) regarding physical performance assessed by 6-min walk test, SPBT, or serum inflammatory markers.
The short performance battery test (SPBT) was used for following-up functional capacity in the patients as it is quick, easy to perform, and useful for monitoring change. Any variation even at one point in SPBT score has clinical significance . After exercise, there was significant increase in the SPBT total score in the exercise group compared to NEG group, P value < 0.001. Also, there was significant increase in the individual components of SBPT in exercise group with no similar changes in the other group and this agrees with other studies that shows significant increase of physical performance and functional capacity of HD patients with exercise [11, 12]. The significant improvement in chair stand test in exercise group reflects an improvement in lower limb muscle strength and endurance post exercise .
Interlukin-6 (IL-6) is considered a strong predictor of inflammation in HD patients . Although there was no difference at baseline between EG and NEG regarding serum IL-6 levels, but at follow-up there was significant difference between EG and NEG group regarding IL-6 levels, P value < 0.05. Serum IL-6 was significantly reduced from 354.2 ± 167.10 to 251.4 ± 123.40 ng/l post-exercise, P value < 0.001. This agrees with the work of Dong et al. that showed significant decrease in IL-6 level after 12 weeks of intradialytic cycling exercise . Another study showed non-significant effect of IDE on in IL-6 levels after 6 months of exercise which may be attributed to smaller sample size . Similarly, serum CRP level significantly decreased in exercise group at 3 months follow-up, P value < 0.001 and there was significant difference between EG and NEG regarding serum CRP levels at follow-up; P value < 0.001 despite the non-significant difference between both groups at baseline. This is supported by previous work which proved that participation in intradialytic exercise reduced inflammatory markers with associated increase in physical performance .
According to Alves et al., higher mortality associated with low serum albumin is dependent on systemic inflammation in ESRD . In this work, the exercise group at follow-up showed significant increase in serum albumin level from 3.9 ± 0.24 to 4.2 ± 0.32 g/dl; P value = 0.05 which may be due to improvement of nutritional and inflammatory status by exercise. Previous work by Dong et al. showed significant increase of serum albumin in dialysis patients’ post-exercise . However, Kato et al. found serum albumin levels increased but not to a significant effect after 1 year of resistance lower limb exercise .
As regards blood hemoglobin level, in our study, there was slight increase in hemoglobin levels post exercise but not reaching significant difference between the 2 groups. According to Gluba-Brzózka et al., the state of chronic low-grade inflammation could exacerbate anemia in dialysis patients influenced by inflammatory cytokines . Perhaps longer duration exercise program could have shown significant improvement in hemoglobin levels post-exercise. Although the work of Chung et al. suggests positive influence of intradialytic exercise on hemoglobin level, Pu et al., in their systemic review, found no association between exercise and hemoglobin levels in dialysis patient [18, 19].
In this work, low to moderate intensity simple aerobic exercise program of few months’ duration proved to ameliorate inflammation and improve physical performance in dialysis patients. The limitations of this work are not measuring dialysis efficacy using the Kt/V formula or follow-up urea reduction ratio. However, the improvement in physical function, serum albumin, and decreased inflammatory markers indicates improved dialysis efficacy in this work. Also, the limitations of this study are the small number of patients and short duration of follow-up. Yet, future studies should focus on effect of longer duration combined aerobic, resistance, and flexibility exercise programs.