BONE MINERAL CONTENT IN 70- AND 75-YEAR-OLD MEN AND WOMEN: AN ANALYSIS OF SOME ANTHROPOMETRIC BACKGROUND FACTORS

The bone mineral content (BMC) in the heel bone of the right foot has been determined in representative samples consisting of 253 men and 309 women aged 70 years, and 105 men and 159 women aged 75, with dual photon absorptiometry in a cross-sectional study. The large number of subjects of the same age makes a detailed analysis of the covariation of anthropometric background variables with the BMC suitable. Lower BMC values at the age of 75 were found for men, but not for women, compared to subjects aged 70. In the present study women at the age of 75 had almost the same mean body weight as those aged 70, while men aged 75 had significantly lower body weight compared to men aged 70. Statistical analysis for conditional dependence showed that, if body weight was kept constant, significantly lower BMC values at the age of 75 were found for women but not for men. Thus, the influence of body weight on BMC seems to be stronger than a cross-sectional age difference of five years. Further analyses showed close correlations between parameters such as body weight, relative weight, body mass index and skinfold thickness with BMC. The more weight the heel bone has to carry, whether it is muscle tissue or fat tissue, the more mineral is found in this bone. It is concluded that, for the lower extremities, body weight must be taken into account in studies of BMC changes, especially in cross-sectional studies and most certainly when analysing the age factor.