Validation of Accelerometers to Assess Physical Activity in Elderly Subjects

Aging is characterized by a decline in physical activity and those who are more active are likely to maintain a better physical functionality. There is however little data on objective measures of physical activity in elderly subjects. The aim of this study was therefore to validate the use of the ActiGraph accelerometer (Manufacturing Technology Inc., Fort Walton Beach, FL) for the assessment of physical activity in the elderly (from the Louisiana Healthy Aging Study) using the doubly labeled water (DLW) technique as the gold standard. Physical activity was measured over a 2-week period in 20 elderly subjects (11 men, 9 women, age 73 ± 8 y, height 1.67 ± 0.10 m, weight 83.3 ± 20.9 kg, body fat by DEXA 35 ± 8%) (mean ± SD) by ActiGraph accelerometers in combination with DLW for total energy expenditure (TEE) and indirect calorimetry for resting metabolic rate (RMR). Correlation analyses were performed between average daily activity counts and different indexes of physical activity: 1) TEE adjusted for fat-free mass and fat mass; 2) TEE adjusted for RMR and 3) TEE divided by RMR. Significant correlations were found between activity counts and the different measures of physical activity by DLW with correlation coefficients of 0.628 (P = 0.003), 0.639 (P = 0.002) and 0.481 (P = 0.03) for model 1, 2 and 3 respectively. In conclusion, these preliminary data show that the ActiGraph accelerometer is a valid method to assess physical activity in healthy elderly volunteers.