Decreased activities of daily living and associations with bone loss among aged residents in a rural Japanese community: the Miyama Study

The present study aimed to clarify frequencies of decreased activities of daily living (ADL) and associations with rate of bone loss among inhabitants more than 60 years old in Miyama, a rural community in Japan. A cohort of 1543 inhabitants aged 40–79 years was established according to Miyama resident registrations in 1989. Men (n = 50) and women (n = 50) from each of two age strata between 60 and 79 years (N = 200) were selected from this cohort, and bone mineral density (BMD) of the lumbar spine and proximal femur was measured using dual-energy X-ray absorptiometry in 1990 (initial survey) and again in 1993, 1997, and 2000. Difficulties involving ADL were surveyed at every follow-up study. Of the 200 initial participants, 124 (57 men, 67 women; 62.0%) completed all BMD measurements and answered all items about ADL in the follow-up survey. The following items were investigated as a general indication of changes to ADL: reaching objects on a high shelf or cupboard (reaching); washing and drying the body (washing body); washing hair over a washbasin (washing hair); sitting for 1 h on a hard chair (sitting); raising the torso from a lying position in bed (raising); standing continuously for 30 min (standing); taking socks on and off the feet (taking socks); bending down from a seated position and picking up a small object at the side of the chair (bending); lifting heavy objects (lifting); and running 100 m without stopping (running). Among ADL items, the most frequent difficulties in men involved running (50.0%), followed by raising (30.6%), standing (27.1%), sitting (24.7%), and reaching (16.5%). In women, difficulties involved running (67.0%), followed by lifting (36.3%), standing (33.1%), reaching (30.8%), and sitting (23.6%). To evaluate relationships between decreased ADL and changes in BMD, annual rates of change for BMD at the lumbar spine and femoral neck were compared to changes for each ADL item (2 grade decrease; 1 grade decrease; or no change). Analysis of covariance (ANCOVA) was then performed on decreased ADL and annual bone changes after adjustment for age, concomitant disease (previous fractures, gastrectomy, diabetes mellitus, and renal dialysis at initial survey). In men, annual rates of change in BMD at the femoral neck over 10 years were significantly correlated with decreased abilities in bending (P = 0.046; R² = 0.10). In women, annual rates of change in BMD at the lumbar spine over 10 years were significantly correlated with decreased abilities in reaching (P = 0.007; R² = 0.25), and lifting (P = 0.014, R² = 0.27), and those at the femoral neck were significantly correlated with decreased abilities in lifting (P = 0.001, R² = 0.33).