One hundred and sixteen community-dwelling premenoposal women aged 35-49 in Inner Mongolia (36 from a city, 39 from a farming village and 41 from a grassland community) were recruited for participation in a study to investigate osteoporosis-related factors. The bone mineral density (BMD) was measured by computed X-ray densitometry (CXD). Hand bone X-rays were taken with an aluminum step-wedge ruler. Anthropometric and several lifestyle data, including workload, exercise, milk drinking, smoking and nutrient intake, were also measured. Markers of bone metabolism, 1, 25 (OH)2D3 and fluoride in drinking water and urine samples were measured. Body height and grip strength were the highest in the city subjects. There were no significant differences in body weight and body mass index (BMI) among the three groups. The percentage of the subjects who were engaged in heavy or moderate workloads was the highest in the village subjects. The village subjects had the lowest percentages of habits of both regular exercise and milk drinking . The percentage of subjects with smoking habit was the highest in the village group. Intakes of calcium and animal protein were the lowest in the village group probably because their diets were mainly composed of grains and vegetables . For both non-dominant and dominant hands, however, the BMD of the second metacarpus were the highest in this group. Univariate logistic regression analysis demonstrated that the subjects who experienced moderate-heavy workload in their 20s and in the present time and those whose grip strength exceeded the average level had significantly higher BMD of non-dominant hand than the remainders, respectively. Multivariate stepwise logistic regression analysis also showed siginificant effects of workload and grip strength on BMD. The levels of bone-alkaline phosphatase (B-Alp) as a marker of bone formation and crosslaps (CL/Cr) as a marker of bone resorption were the highest in the grassland group. The level of 1, 25 (OH)2D3 was about 1.5 times higher in the grassland group compared with the city and village groups. Furthermore, the concentration of fluoride in drinking water and urine samples were about 5 times higher in the grassland group than other two groups . In the grassland group, concentration of fluoride in urine was positively correlated with B-Alp (r=0.34, p<0.05) and CL/Cr (r=0.39, p<0.05), respectively. These findings suggest that high workload and grip strength play important roles on BMD among women living in farming village of Inner Mongolia. Despite higher milk intake, the biological markers of bone metabolism among the grassland subjects showed postmenopausal pattern, suggesting the effects of high fluoride level in drinking water.
