Exercise effects on hip bone mineral density in older, post-menopausal breast cancer survivors are age dependent

We evaluated whether age moderated the effect of impact + resistance exercise on hip BMD in older post-menopausal breast cancer survivors (BCS). Exercise was more beneficial among younger than older women within our sample, suggesting that much older BCS may require different training programs to improve hip health. Purpose: Previously, we reported that a program of resistance + impact training stopped bone loss at the spine in older, post-menopausal BCS but had no effect on bone mineral density (BMD) at the hip. Aging may blunt the responsiveness of the hip to mechanical loading, so we conducted a secondary data analysis to evaluate whether age moderated the effect of exercise on hip BMD. Methods: We analyzed data from our randomized, controlled trial in older (≥ 50 years of age at diagnosis), post-menopausal, post-adjuvant treatment BCS (n = 106) comparing women assigned to impact + resistance exercise (POWIR) or to a control program of low-intensity stretching (FLEX). We examined effect modification by age on BMD at three hip sites (greater trochanter, femoral neck, and total hip) using hierarchical linear modeling adjusting for time since diagnosis and use of adjuvant hormone therapy. Results: Age moderated the effect of exercise on total hip BMD such that younger women in POWIR were more likely to see a positive net benefit than FLEX compared to older women where there was little difference between groups (p = 0.02). Conclusions: The skeletal response to loading at the hip within post-menopausal BCS diminishes with age. Whether more vigorous exercise programs and/or longer training periods are required to favorably change hip health in older BCS will require future study and careful thought about the risks and benefits of tougher training programs.