Accelerometer-measured daily physical activity among octogenerians: results and associations to other indices of physical performance and bone density

Information on objectively assessed physical activity in elderly people is scarce. The aim of this study was to investigate accelerometer measures in elderly women, and its relation to other indices of physical activity and bone density. A subset of 57 women, all 80 years old, (range 80.0–80.7) of the Malmö OPRA study was equipped with an MTI accelerometer for a period of 5–7 days. A 7-day activity log was used. At baseline a self-assessment questionnaire was used and isometric muscle strength (knee), gait speed, balance and bone density measurements [dual-energy X-ray absorptiometry (total body, hip, and spine), and quantitative ultrasound of the calcaneus] were measured. About 14% (8 out of 57) had a moderate to vigorous physical activity (MVPA) (>1,952 counts per min [CPM]) exceeding 30 min/day. The median CPM was 18. When compared to questionnaire data, the correlation between MVPA and physical activity was 0.50 (P < 0.001). The corresponding result for CPM was 0.48, P < 0.001. When compared to the activity log, the correlation between MVPA and physical activity away from home was 0.49 (P < 0.001). The corresponding result for CPM was 0.55, P < 0.001. The correlation between MVPA and gait speed was 0.41 (P = 0.002). The corresponding result for CPM was 0.40, P = 0.002. There were no correlations to the measurements of muscle strength, balance or bone density (all P ≥ 0.07). Accelerometers can be used for measuring of physical activity also of the elderly. Questions on daily physical activity correlated modestly with accelerometer results in elderly women. Accelerometer results were not correlated to measures of balance, muscle strength and bone density.