Assessment of habitual physical activity and energy expenditure in dialysis patients and relationships to nutritional parameters

Background and aim: Assessment of physical activity level and of energy expenditure is important in the clinical and nutritional care of dialysis patients, but it is not so easy to accomplish. The SenseWear (TM) Armband (SWA) is a novel multisensory device that is worn on the upper arm and collects a variety of physiologic data related to physical activity. Thus, duration and intensity of physical activity is recorded and expressed as METs (Metabolic Equivalent Task), and energy expenditure is estimated. The aim of our study was to assess interdialytic spontaneous physical activity in stable chronic hemodialysis (HD) patients and the relation to nutritional status and dietary nutrient intake. Patients and methods: In 50 stable patients on maintenance hemodialysis treatment and 33 normal subjects (control group), level of spontaneous physical activity and estimated daily energy expenditure was assessed by SWA and related to biochemistry and anthropometry data, bioelectric impedance vector analysis, and energy and nutrient intake information coming from a 3-day food recall. Results: In respect to controls, HD patients showed lower mean daily METs value (1.3 +/- 0.3 vs. 1.5 +/- 0.2, p < 0.01), a lower time spent on activities > 3 METs (89 +/- 85 vs. 143 +/- 104 min/day, p < 0.05), lower number of steps per day (5,584 3,734 vs. 11,735 5,130, p < 0.001), resulting in a lower estimated energy expenditure (2,190 +/- 629 vs. 2,462 +/- 443 Kcal/day, p < 0.05). 31 out of the 50 HD patients (62%) had a mean daily value < 1.4 METs and hence were defined as sedentary. They differed from the active patients for higher age (63 +/- 12 vs. 54 +/- 12 y, p < 0.01), lower energy intake (26.1 +/- 6.4 vs. 32.4 +/- 11.3 Kcal/day, p < 0.05) and lower phase angle (5.5 +/- 1.0 vs. 6.3 +/- 0.9, p < 0.05). SWA-based estimation of daily energy expenditure was negatively related to age (r = -0.31, p < 0.05), whereas positive relations were observed with HMI (r = 0.51, p < 0.001), phase angle (r = 0.40, p < 0.01), serum phosphate (r = 0.49, p < 0.001) and albumin (r = 0.41, p < 0.01). The mean daily METs values were strongly related to normalized energy intake (r = 0.47, p < 0.001) and also to protein intake (r = 0.33, p < 0.05) and to phase angle (r = 0.38, p < 0.01). Multiple regression analysis showed that energy intake and dietary protein intake were independently related to the intensity of physical activity. Conclusion: Our findings indicate that poor physical activity is highly prevalent in stable dialysis patients even when free from physical or neurological disabilities or severe comorbid conditions. The level and intensity of physical activity is positively related to body composition and to dietary nutrient intake. This confirms the strong interrelationship between exercise and nutrition, which in turn are associated with survival, rehabilitation and quality of life in dialysis patients.