Inactivity Is Associated with Impaired Physical Fitness and Quality of Life in Ambulatory Patients Under Chronic Hemodialysis

Research Objectives: To investigate the association of inactivity with physical fitness(main) and disease-specific quality of life(secondary) in ambulatory chronic hemodialysis patients.

Design: This cross-sectional study evaluated the physical fitness of each participant using cardiopulmonary exercise testing(CPET), isokinetic dynamometry(isok), and body composition analysis via dual-energy X-ray absorptiometry(DXA). Participants also received the HK Chinese Kidney Disease Quality of Life(KDQOL) assessment and the International Physical Activity Questionnaire. A sedentary lifestyle was defined as a total physical activity(TPA) of less than 577.5 MET-min.

Setting: All the participants underwent regular hemodialysis(HD) in the outpatient hemodialysis unit in referral centers for institutional practice.

Participants: Eligibility criteria included 62 referred samples receiving hemodialysis for more than three months, capable of walking independently for over 10 meters, and aging over 20 years old. Exclusion criteria comprised medical, physical, and mental comorbidities that contraindicated exercise, unstable cardiac conditions, and disabling orthopedic and neuromuscular diseases.

Interventions: Not applicable.

Main Outcome Measures: This study demonstrated that inactivity was associated with reduced cardiopulmonary fitness, diminished muscle strength, and adverse body composition, all contributing to impaired physical fitness. Inactivity was also associated with lower KDQOL scores across multiple domains and was the only major predictor of the physical composite score(PCS) of KDQOL.

Results: In CPET, TPA was positively correlated with peak work rate, total and body-weight-normalized peak oxygen consumption(V̇O2), peak minute ventilation(V̇e), ventilatory anaerobic threshold(VAT), and oxygen uptake efficiency slope(p-value < 0.001 to 0.047). TPA was negatively correlated with resting heart rate, lowest value of ventilatory equivalent for CO2(EqCO2 nadir), and V̇e to CO2 production(V̇e-V̇CO2) slope(p-value= 0.024 to 0.039). In isok, TPA showed positive correlations with hand grip strength(HGS), isometric peak torque, 120-degree peak torque, total work, and work in the last third of the 20-repetition fatigue test(p-value < 0.001 to 0.039). In DXA, TPA correlated positively with bone mineral content and lean mass of the right leg, left leg, and total body(p-value < 0.001 to 0.031). Sedentary behavior showed similar correlations with CPET, isokinetic, and DXA variables and with sarcopenia(p-value= 0.017). Moreover, inactivity was associated with lower KDQOL scores across multiple domains(p-value < 0.001 to 0.050) and was the primary predictor of the PCS of KDQOL(standard regression coefficient: -0.447, p-value= 0.006).

Conclusions: Ambulatory chronic HD patients exhibited a high prevalence of low peak V̇O2, sarcopenia, and sedentary behavior. Inactivity was associated with reduced cardiopulmonary fitness, decreased muscle strength, endurance and mass, and increased sarcopenia prevalence. Moreover, a sedentary lifestyle was a primary determinant of the physical component score in KDQOL.

Author(s) Disclosures: The authors declared no conflict of interest.