Objectively Measured Physical Activity and Changes in Life-Space Mobility Among Older People.

Background: Our aim was to study the relationship between objectively measured physical activity and subsequent changes in life-space mobility over 2 years among older people. Life-space mobility refers to the area a person moves through in daily life, taking into account frequency, and need of assistance. Life-space mobility and physical activity correlate, but whether different intensities of objectively assessed physical activity predicts decline in life-space mobility is not known.

Methods: Prospective cohort study of the "Life-space Mobility in Old Age" (LISPE) project accelerometer substudy. Participants were community-dwelling older people aged 75-90 (n = 164). Life-space mobility was measured with the Life-Space Assessment at baseline face-to-face home interview and telephone follow-up interviews 1 and 2 years after baseline. Physical activity (step count and time spent in moderate activity, low activity, and sedentary behavior) was measured by a tri-axial accelerometer (Hookie "AM20 Activity Meter") for 7 days at baseline. Generalized estimating equations (GEE models) were used to compare changes in life-space mobility between participants categorized according to the baseline physical activity measures.

Results: Median age of the participants was 79.5 (IQR 6.7) and 64% were women. Over the 2 years, life-space mobility declined significantly among those with lower step counts and less time spent in moderate activity measured at baseline. Time spent in low activity and sedentary behavior did not predict changes in life-space mobility.

Conclusions: In old age, more time spent walking outdoors and accumulation of moderate-intensity physical activity may help to maintain higher life-space mobility, a correlate of good quality of life.