Objective To investigate the effects of blood biochemical indicators on physical functional status and exercise duration in patients with chronic kidney disease (CKD) in stages 3-5.

Methods A total of 156 patients with stages 3-5 CKD admitted to our hospital between March 2021 and February 2024 were enrolled in the study. General information questionnaires, the Karnofsky Performance Status (KPS) scale of functional status, and the International Physical Activity Questionnaire-Long Form (IPAQ-L) were used for data collection. Blood biochemical indicators were assessed through blood tests. Patients who engaged in physical activity meeting the recommended standards of the CKD clinical practice guidelines were defined as the high-level exercise group, while the others were defined as the low-level exercise group. Pearson correlation analysis was performed to examine the relationship between blood biochemical indicators, physical functional status, and exercise duration. Multiple linear regression was performed to identify factors influencing exercise duration. The SPSS macro program Process 4.1 was used to analyze the mediating effect.

Results The average KPS score of the 156 patients with stage 3-5 CKD was 77.03 ± 11.99, and the average weekly exercise duration was (71.67 ± 10.16) min. Compared with the high-level group, the low-level group had lower hemoglobin (Hb) (94.76 ± 16.98 g/L) and serum albumin (Alb) (30.96 ± 6.35 g/L) levels and a higher blood urea nitrogen (BUN) (13.45 ± 3.28 mmol/L) level (P < 0.05). Hb levels were positively correlated with physical functional status (r = 0.248, 95% CI: 0.085 to 0.402) and exercise duration (r = 0.231, 95% CI: 0.081 to 0.372). Alb was positively correlated with physical functional status (r = 0.192, 95% CI: 0.044 to 0.329) and exercise duration (r = 0.238, 95% CI: 0.071 to 0.380). BUN was negatively correlated with physical functional status (r = －0.277, 95% CI: －0.404 to －0.115) and exercise duration (r = －0.277, 95% CI: －0.397 to －0.142). Physical functional status was positively correlated with exercise duration (r=0.240, 95% CI: 0.084 to 0.375). The factors influencing exercise duration were Hb (β = 0.160, 95% CI: 0.004 to 0.179), Alb (β = 0.162, 95% CI: 0.011 to 0.460), and BUN (β = －0.221, 95% CI: －1.199 to －0.220) levels (P < 0.05). The physical functional status played a partial mediating role between blood biochemical indicators and exercise duration, accounting for 20.45%, 16.14%, and 17.55% of the total effects of Hb, Alb, and BUN on exercise duration, respectively.

Conclusion Hb, Alb, and BUN can directly affect the exercise duration of patients with CKD in stages 3-5, and can also indirectly affect the exercise duration of patients through physical functional status.