Bone density of the spine and femur in adult white females

We measured bone mineral density (BMD in g/cm(2)) of the spine (L2-L4) and femur (four regions) in 1472 and 1487 cases, respectively, of ambulatory wh ite women ages 20-79 years in the USA. A DPX densitometer was used in a mob ile setting. The BMD values for women up to 69 years corresponded closely w ith published values for the USA, the UK, and northern Europe; our values w ere somewhat lower than those from other studies only in women over 70 year s. The USA data were combined with data from Europe to give reference curve s on about 12,000 subjects. Decreases of BMD with age in women below 50 yea rs were much smaller than in older women (0.2% versus 0.6-1.0% per year). F emoral bone decreased from the neck region, but not the trochanter with age ; the decrease of total femur BMD with age was due to loss from the former region. Loss of bone mineral content (BMC in g) from the femur neck and tot al femur region did not accelerate until after age 50 years, much like the spine. The apparent decrease of BMD in these regions that begins about age 40 actually is due to an increase of bone area. About 20% of USA women aged 50-79 years had BMD levels for the lumbar spine, or for the femur neck, mo re than -2.5 SD below the average values in young adult women 20-39 years o ld. Body weight had several times more impact on BMD than height, and in fa ct, a change of 1 kg in postmenopausal women was commensurate with the effe ct of a 1-year change in age. Subjects in the lowest quartile of body weigh t had T-scores that were 1 SD below those in the highest quartile.