ASSESSMENT OF AGE-RELATED BONE LOSS IN NORMAL SOUTH-AFRICAN WOMEN BY MEANS OF THE HOLOGIC QDR-1000 SYSTEM

The aim of this study was to evaluate age-related changes in cortical and trabecular bone mineral density (BMD) in South African subjects, a nd to develop a local reference database for dual energy X-ray absorpt iometry with the QDR 1000 densitometer. A questionnaire was used to re cruit volunteers. Age, years since menopause, use of medications and m edical diseases were recorded. Men were excluded. Only whites and colo ureds were studied. Three hundred and eleven women had single measurem ents over a 2-year period. Seven sets of subjects were defined accordi ng to age (18 - 44; 45 - 49; 50 - 54; 55 - 59; 60 - 64; 65 - 69; > 70 years) (N = 163; 32; 35; 23; 25; 16; 17 respectively). Height and weig ht did not change significantly with age. There were significant diffe rences in lumbar and femoral BMD (Ward's) compared with those of Ameri can subjects in the different age categories. Both the lumbar and tota l femoral BMD began to fall significantly between the ages of 60 and 6 5 years (P < 0,01). Ward's triangle showed a significant fall in BMD b etween 45 and 50 years of age (P < 0,01). Ward's BMD predicted 36% of the variation in lumbar BMD at 45 years but 10% at 70 years. Ward's tr iangle is a useful predictor of femoral bone loss in later years. The fracture threshold at the lumbar vertebrae was 0,822 g/cm(2); at Ward' s triangle it was 0,443 g/cm(2). This gave a 16% prevalence of osteope nia in the lumbar region and a prevalence of 24% at Ward's area.