Physical activity and 5-year changes in physical performance tests and bone mineral density in postmenopausal women: the Yokogoshi Study

Objective: The effect of physical activity on musculoskeletal health in older adults is not completely understood. The aim of this study was to determine the relationship between physical activity and 5-year changes in physical performance tests and bone mineral density (BMD) in postmenopausal women.

Study design: The design was a 5-year cohort study.

Main outcome measures: Subjects were 507 women (55-74 years old) living in a rural community in Japan. Physical activity assessed included housework, farm work, and moderate leisure-time physical activity within the previous week. Measurements at baseline included handgrip strength, walking time (timed "Up & Go" test) and BMD of the femoral neck and vertebrae. Five-year changes in these measures (outcome variables) were compared among groups with different levels of physical activity by analysis of covariance.

Results: Women who did not do housework performed worse in changes in handgrip strength (difference=2.22 kg, P=0.0201) and worse in changes in the walking time (difference=0.54 s, P=0.0072) than those who did housework alone. Women who spent at least 9h per week (median=24) doing farm work performed better in changes in handgrip strength (difference=0.28 kg, P=0.0334), but worse in changes in the walking time (difference=0.66 s, P<0.0001) than those who did not do farm work. However, leisure-time activity was not associated with changes in any outcome variable, and none of the physical activities predicted BMD changes.

Conclusions: Engaging in housework and farm work are determinants of physical function in postmenopausal women, which may help them maintain independence in daily living.