Bone mineral density (BMD) was measured over a ten year period in a cohort study in Miyama village, Wakayama Prefecture, Japan, to provide information on rate of bone loss in the mature and elderly population. Four hundred subjects were selected by sex and age decade from the full list of residents born in 1910-1949, and aged 40-79 years at the end of 1989, with 50 men and 50 women in each age decade. Baseline BMD of the lumbar spine and the proximal femur was measured using dual energy X-ray absorptiometry (DXA) in 1990 and again in 1993, 1997 and 2000. Annual rate of change in BMD (% per year) in the lumbar spine in men in their forties, fifties, sixties and seventies was 0.17, 0.55, 0.01 and -0.16, respectively, and in women, -0.87, -0.83, -0.48 and -0.48, respectively. Thus in men, BMD at the lumbar spine increased in all age strata but the oldest, when it decreased, whereas in women, it decreased in all age strata. On the other hand, BMD at the proximal femur decreased in both sexes in all age strata. Our results show that bone loss rates differ depending on the site involved, demonstrating that different strategies are needed for the prevention of bone loss in the spine and hip.Furthermore, we found evidence of differences in BMD for given age strata between birth cohorts. Data in 1990 and in 2000 showed significant improvements for men in their sixties and for women in their fifties, suggesting that future problems of osteoporosis might be less severe than has previously been predicted in Japan.

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The aim of this study was to clarify and compare the temporal course of bone mineral density (BMD) between fast bone losers and normal residents in Miyama Village, a rural Japanese community. BMD was measured over a 10-year period in a cohort study in Miyama Village, Wakayama Prefecture, Japan, to provide information on rate of bone loss in the mature and elderly population. Subjects ( n=400) were selected by sex and age stratum from the full list of residents born in 1910-1949, with 50 men and 50 women in each age decade. Baseline BMD of the lumbar spine and proximal femur was measured using dual energy X-ray absorptiometry in 1990, 1993, 1997 and 2000. In the cohort, 171 men and 189 women completed the follow-up survey performed in 1993. After calculating the rate of bone loss between 1990 and 1993, the greatest tertile from the distribution of bone loss was categorized as fast bone losers, with the remainder considered as normal subjects. Changes in BMD were compared between normal subjects and fast bone losers over the 10-year period. Mean rate of change for BMD at both lumbar spine and femoral neck in fast bone losers recovered to levels similar to those in normal subjects over 7 years of observation. By contrast, BMD at the lumbar spine and femoral neck decreased steeply over the 10-year period in both groups, and mean BMD for fast bone losers was significantly lower than that of normal subjects ( P<0.05). These differences were apparent only at the lumbar spine in both men and women, even after adjusting for age. These results indicate that fast bone loss is a transient phenomenon rather than a fixed status, although individuals who have been categorized as fast bone losers at some stage continue to display low BMD in the lumbar spine.

Reference values of bone mineral density (BMD) have mainly been based on hospital volunteers in Japan. Consequently, these values may be inappropriate for the use as a standard in the osteoporotic study. In order to establish reference values, BMD was measured of 400 age-stratified inhabitants of Miyama Village, utilizing dual energy x-ray absorptiometry (DEXA).The mean BMD of L2-L4 in males in each age group was 1.19-+ 0.16 g/cm 2 (mean + standard deviation) in 40's, 1.15 _+ 0.19 g/cm 2 in 50's, 1.03 -+ 0.18 g/cm 2 in 60's and 1.06 -+ 0.25 g/cm 2 in 70's. The difference of BMD was statistically significant between the 50 and 60 age groups. On the other hand, in females the mean BMD of L2-L4 was 1.18 + 0.16 g/cm 2 in 40's, 0.99-+0.18 g/cm 2 in 50's, 0.84_+0.19 g/cm 2 in 60's and 0.78_+0.17 g/cm 2 in 70's. The BMD was significantly lower in the 50 age group than in the 40 age group and was similarly lower in the 60 age group than in the 50 age group.The mean BMD of femoral neck in males was 0.98_+0.14 g/cm 2 in 40's, 0.91_+0.12 g/cm 2 in 50's, 0.83_+0.11 g/cm 2 in 60's and 0.78_+0.11 g/cm 2 in 70's. In females, the BMD of femoral neck was 0.88 -+ 0.11 g/cm 2 in 40's, 0.75 -+ 0.11 g/cm 2 in 50's, 0.68 _+ 0.11 g/cm 2 in 60's and 0.63-+0.10 g/cm 2 in 70's. BMD of the femoral neck in an older age group was lower than that in a younger age group both in males and females.

Femoral neck fracture at Wakayama Prefecture was surveyed in 1988.Questionnaires were sent to all clinics and hospitals totaling 109 equipped for orthopaedic and general surgeries through Wakayama Prefecture. Wakayama Prefecture is located in the southernmost peninsula of main island in Japan, and has a mild climate throughout the year. Number of femoral neck fractures were reported 159 in males and 509 in females. The inicidence of femoral neck fracture per 1,000 population was 0.61. The incidence increased concomitant with aging. The incidence of intra-and extracapsular fractures was equal in females. In both sexes, the incidence of intracapsular fracture was the highest in the age group 70-79, and that of extracapsular fractures was highest in the eighties. The incidence among males was one half to one third in comparison with that of females. Seasonal and regional differences were not observed in Wakayama Prefecture.