RELATIONSHIPS BETWEEN BONE MASS MEASUREMENTS AND LIFETIME PHYSICAL-ACTIVITY IN A SWEDISH POPULATION

Lifetime occupational and leisure time activities were assessed by a q uestionnaire in order to evaluate their relationship to bone mass meas urements and biochemical markers of bone metabolism in a population of 61 women and 61 men, randomly selected from a Swedish population regi ster, to represent ages between 22 and 85 years. We also considered po ssible confounders by using questions about smoking habits, milk consu mption, hormone replacement therapy (HRT), and menopausal age. Bone mi neral density (BMD) and bone mineral content (bone mass, BMC) of the t otal body, lumbar spine, and proximal femur (neck, trochanter, Ward's triangle) were measured by dual energy X-ray absorptiometry (DXA), and BMD of the forearm with single energy X-ray absorptiometry (SXA). In addition, both DXA and SXA provided information on bone area. Quantita tive ultrasound measurements (QUS) at the heel were performed to asses s the speed of sound (SOS) and broadband ultrasound attenuation (BUA). Easting blood samples were analyzed for biochemical markers of bone m etabolism as well as parathyroid hormone (PTH) and total serum calcium . After adjustment for confounding factors, neither BMD nor QUS measur ements were consistently related to lifetime leisure time or occupatio nal activities; nor were there any consistent patterns relating bioche mical markers of bone metabolism to bone mass measurements. However, p hysical activity seemed to influence bone mass, area, and width more t han density. In men, high levels of leisure time activity were associa ted with raised values for lumbar spine area (6.2%) and width (3.3%) a s well as for femoral neck area (5.5%) compared with their low activit y counterpart. Men exposed to high levels of occupational activity dem onstrated lower lumbar spine BMD (10.9%) and area (5.3%) than men with low activity levels. Within an unselected Swedish population, estimat ion of lifetime occupational and sport activities as well as bedrest, using a questionnaire, demonstrated no major effects on bone density. However, the association between high levels of lifetime activity and raised values for bone mass, area, and width indicate that geometrical changes in bone may provide better estimations of mechanically induce d bone strength than bone density, at least in men.