The effect of water fluoridation on the bone mineral density of young women.

INTRODUCTION: Osteogenic effects of therapeutic fluoride have been reported; however, the impact of exposure to low level water fluoridation on bone density is not clear. We investigated the effect of long-term exposure to fluoridated water from growth to young adulthood on bone mineral density (BMD). METHODS: BMD was measured in 24 healthy women from Regina (fluoride 0.1 mg/L) and 33 from Saskatoon (fluoride 1.0 mg/L), with no differences between groups for height, weight, lifestyle or dietary factors. RESULTS: Saskatoon women had significantly higher mean BMD at total anterior-posterior lumbar spine (APS) and estimated volumetric 1.3 (VLS), with no difference at total body (TB) or proximal femur (PF). CONCLUSION: Exposure to water fluoridation during the growing years may have a positive impact on axial spine bone density in young women.

Comparison of areal and estimated volumetric bone mineral density values between older men and women.

We compared areal bone mineral density (BMD) of the total body (TBMD), antero-posterior lumbar spine at L3 (APS), lateral spine at L3 (LS) and femoral neck (FN). In order to understand better the effect of gender-related size differences on BMD, we also compared the estimated volumetric BMD at L3 (VLS) and the femoral neck (VFN). Subjects were asymptomatic women (n = 22) and men (n = 44) with an age range of 58-79 years. BMD at each site was measured by dual-energy X-ray absorptiometry using a Hologic 2000 in array mode. Results of the statistical analyses (ANOVA) showed the men to have significantly greater BMD at all areal sites [APS, LS (p < 0.05); FN (p < 0.01); TBMD (p < 0.001)]. The two estimated volumetric comparisons, however, showed no gender differences. Results demonstrate how measures from areal BMD measures can be misleading when comparing groups of different size. In older men and women planar measures may overestimate gender differences in BMD.

Bone tissue and physical activity.

Bones provide more than just a structural framework for the body. In reality, bone is a multifunctional tissue dependent on, and sensitive to, a wide variety of biological, biochemical and biomechanical stimuli. This complex system is highly responsive to the mechanical stresses imposed by gravity and muscular contractions. Animal studies as well as human cross-sectional and longitudinal studies all point to the importance of weight-bearing physical activity and mechanical loading as the prime modalities in the preservation of skeletal integrity. Lack of weight-bearing activity is extremely harmful to the skeleton. Loss of skeletal density in individuals subjected to various types of immobilization or under conditions of weightlessness is well documented. The role of physical activity in the maintenance of skeletal integrity is a topic of considerable current interest when the increasing incidence of skeletal fragility in the elderly is taken into account.

Effects of physical activity, dietary calcium intake and selected lifestyle factors on bone density in young women.

To assess the possible effects of physical activity, calcium intake and lifestyle factors on bone density, we measured the calcaneal bone density of 101 healthy female volunteers aged 20 to 35 years. Information was obtained through questionnaires and 1-week and 2-week recall tests. There appeared to be no relation between height, weight or age and bone density in the study sample. Childhood milk consumption, current dietary calcium intake, level of avocational physical activity and lifestyle variables such as cigarette smoking and coffee consumption, considered separately, did not reach statistically significant levels as determinants of bone density. Childhood physical activity level appeared to have a significant positive effect on bone density.

Epidemiology of fractures of the distal end of the radius in children as associated with growth.

We determined the annual incidence of fracture of the distal end of the radius for patients of all ages and both sexes in the province of Saskatchewan, using two data sets: data on hospital admissions for 1970 through 1984, and data on physician billing for 1978 through 1985. The rate of occurrence of this fracture in children, by age and sex, was compared with longitudinal data on the velocity of growth that was collected during the same time for children from the same population. We compared the incidences of the fracture with the results of studies on the levels of activity in children and adolescents during growth. We also compared the age-specific incidence of the fracture in children with the incidence in adults. For both data sets, the age at the peak incidence of fracture of the distal end of the radius almost perfectly matched the age at which peak velocity of growth in height occurs for boys and girls. For girls, the peak incidence occurred between the ages of 11.5 and 12.5 years and for boys, between 13.5 and 14.5 years; these ages corresponded to the mean peak velocity of growth at 11.9 years for girls and 14.3 years for boys. The age-adjusted incidence of the fracture in male subjects was highest at fourteen years and was not exceeded by that in female subjects until fifty-three to fifty-four years.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone dynamics: stress, strain and fracture.

Bone is a dynamic tissue whose functional mass is controlled by the balance between the endocrine drive towards bone resorption and the mechanically-engendered drive towards bone formation. Strain is the key intermediate variable between loading forces and bone remodelling. Animal studies have shown that static loading of bone has no osteogenic effect; bone loss occurs as if there were no loading at all. However, dynamic loading, that is, cyclic change in internal strain, is strongly osteogenic, with relatively few cycles required for maximum effect. However, if a sufficient number of cycles is applied, repetitive loading can cause stress fractures. This number decreases as internal strains increase. Thus strain redistribution within bone, as caused by muscle fatigue or improper sports equipment, is a significant cause of fracture.