Physical activity levels in patients on hemodialysis and healthy sedentary controls

Physical activity levels in patients on hemodialysis and healthy It has long been known that patients on dialysis are sedentary controls. debilitated (1, 2) and report low levels of physical func- Background. Patients on dialysis have reduced exercise tol- tioning on questionnaires (3). Anemia was believed to erance compared with age-matched sedentary controls. The be an important reason for the reduced functional capac- reasons for this debility have not been fully elucidated, but ity of these patients, and improvements were noted after physical inactivity could be a contributing factor. The purpose of the current study was to determine whether patients on the introduction of recombinant erythropoietin (4, 5). hemodialysis are less active than healthy sedentary controls However, erythropoietin treatment does not restore ex- and to explore clinical correlates of physical activity level in a ercise capacity to normal levels in dialysis patients (6-8). group of hemodialysis patients. It is now apparent that a muscle defect accounts for at Methods. Thirty-four hemodialysis patients and 80 healthy sedentary individuals participated in the study. Physical activity least a part of the reduced physical functioning in this was measured for seven days with a three-dimensional acceler- group (9, 10). The exact nature of the muscle defect is ometer and with an activity questionnaire. not clear, but morphologic studies have shown changes Results. Vector magnitude values from the accelerometer in uremic muscle that are consistent with atrophy (9, 11). for the dialysis and control subjects were 104,718 6 9631 and Inactivity is a common cause of muscle atrophy and 161,255 6 6792 arbitrary units per day, respectively (P , 0.0001, mean 6 SEM). The estimated energy expenditure values de- could be a contributing factor to the muscle abnormali- rived from the questionnaire were 33.6 6 0.5 kcal/kg/day and ties and reduced functional status of the dialysis popula- 36.2 6 0.5 kcal/kg/day (P 5 0.002). The difference between tion. Alternatively, uremia itself or hormonal abnormali- patients on dialysis and controls increased with advancing age. ties associated with uremia, such as hyperparathyroidism Among the dialysis subjects, some measures of nutritional sta- tus correlated with physical activity level, including serum albu- or resistance to growth hormone, may result in muscle min concentration (r 5 0.58, P 5 0.003), serum creatinine atrophy and may thus contribute to inactivity. However, concentration (r 5 0.37, P 5 0.03), and phase angle derived few studies of physical activity have been performed in from bioelectrical impedance analysis (r 5 0.40, P 5 0.02). the end-stage renal disease (ESRD) population. Infor- Conclusions. Patients on hemodialysis are less active than mation about physical activity levels could be important healthy sedentary controls, and this difference is more pro- nounced among older individuals. There is an association be- for identifying patients in need of physical therapy or tween the level of physical activity and nutritional status among other interventions designed to increase mobility. More- patients on dialysis. These findings are of great concern, given over, if levels of physical activity are low in dialysis pa- the trend toward increasing age in incident dialysis patients and tients or in a subset of patients, raising activity levels the well-known association between inactivity and increased mortality in the general population. could be beneficial since it is well established that in- creasing physical activity reduces the risk of cardiovascu- lar disease in the general population (12). The major goals of the study were to measure physical activity levels in patients on dialysis and to compare these levels with healthy sedentary controls. We also