Bone mass of spine and forearm in osteoporosis and in German normals: influences of sex, age and anthropometric parameters

We measured forearm bone mineral density (BMD) using single photon absorptiometry (SPA) and bone mineral content (BMC) and BMD of lumbar spine by dual photon absorptiometry (DPA). The population consisted of 463 bone healthy subjects, 346 females and 117 males aged 20–85 years. Any underlying bone disease or other diseases known to affect bone mass were excluded by physical examination, thoracic and lumbar radiographs and laboratory screening. Patients with osteoarthritis of lumbar spine were excluded as well as patients taking drugs known to affect bone mass. All bone mass values declined with age. Body height also declined with age by 1.2 cm and 1.8 cm per 10 years (— 0.7% and — 1 %) in females and males respectively. Main effects of age, body height, ‐surface, ‐weight and ‐mass index on bone mass were calculated using multiple regression models. In males and females lumbar BMC measured in gHA depended primarily on body height and secondarily on age. Spinal BMD as measured in g cm‐2 was primarily dependent on age and then on height. In females forearm BMD depended primarily on age and then on body surface, in males on body surface only. Using receiver operating characteristic (ROC) analysis the ROC area increased from 0.81–0.85 (n.s.) including body height into spinal BMD values leading to a higher sensitivity of measurements of spinal bone mass in recognizing 58 patients with spinal postmeno‐pausal osteoporosis. Including body surface into forearm BMD measurements ROC area increased from 0.66–0.69 (P=0.055). We conclude from these data that measurements of bone mass not only depend on age and sex, but on body height and surface. These anthropometric parameters and their changes over decades have to be taken into account when examining any effects on bone mass in cross‐sectional studies. Including these parameters into bone mass values may lead to higher sensitivity of the method.