Effect of lifetime occupational physical activity on indices of bone mineral status in healthy postmenopausal women.

The purpose of this study was to examine the effect of lifetime physical activity of farmers on skeletal status. Seventy-one healthy, postmenopausal women (mean age 52.3 +/- 5.9 years, range 42-61 years) who worked professionally on farms were compared with 78 matched controls (mean age 51.8 +/- 5.5 years, range 42-61 years). Broadband ultrasound attenuation (BUA) and speed of sound (SOS) at the os calcis were measured using an ultrasound transmission imaging system. Bone mineral density (BMD) of the lumbar spine and femoral neck were measured by dual-energy X-ray absorptiometry (DXA). Differences in BUA, SOS, and BMD between farmers and controls were expressed relative to standard deviation (SD) of the farmers. Farmers had significantly higher density values than controls (difference = 1.3 SD in the spine and 1.5 SD in the femoral neck, P < 0.0001 for both comparisons). Ultrasound values were significantly higher in the farmers compared with the controls in calcaneus (difference = 1.1 SD for BUA and 0.7 SD for SOS, P < 0.0001 for both comparisons). The difference of spine BMD, femoral neck BMD, BUA, and SOS between farmers and controls, as judged by comparison of the slopes of the regression lines, was unchanged with age and years since menopause. These results suggest that lifetime physical activity has a positive effect on bone status of postmenopausal farmers.