Self-reported lifetime physical activity and areal bone mineral density in healthy postmenopausal women: the importance of teenage activity.
Girls who exercise athletically have higher bone mass than their sedentary counterparts, and this difference may be sustained in adulthood. However, whether moderate physical activity during youth confers lasting benefits for bone is unclear. We explored lifetime physical activity and current areal bone mineral density (aBMD) in 78 postmenopausal women with no known history of osteoporosis. Subjects reported physical activity for four age periods (12-18, 19-34, 35-49, > or = 50 years) using the Historical Leisure Activity Questionnaire, completed two 3-day food records, had measurements of height and weight, and aBMD assessed using dual-energy X-ray absorptiometry at the lumbar spine (L1-4) and proximal femora. Low aBMD was detected at the lumbar spine in 43 (56%) women and at the proximal femora in 38 (49%) women. Teenage physical activity, but not activity during other age periods, was associated with current aBMD at both sites (lumbar spine r = 0.31, P < 0.01; mean proximal femora r = 0.33, P < 0.01). Weight-bearing physical activity (WBPA) at age 12-18 years was the only predictor of current lumbar spine aBMD (R (2) = 0.110, P = 0.004). Current proximal femoral aBMD was positively predicted by physical activity at age 12-18 years and negatively predicted by current age (R (2) = 0.175, P = 0.001). Subjects above the median of teen WBPA had 5-8% higher current aBMD than those reporting less teen WBPA and were less likely to be classified with osteopenia or osteoporosis. Moderate physical activity during years of peak bone acquisition appears to have lasting benefits for lumbar spine and proximal femoral aBMD in postmenopausal women.