Are associations between physical activity and bone mineral density in adults sex- and age-dependent? An analysis of the UK biobank study

Montgomery, Gallin, Yusuf, Mohamed, Cooper, Rachel and Ireland, Alex ORCID: https://orcid.org/0000-0003-1094-9183 (2024) Are associations between physical activity and bone mineral density in adults sex- and age-dependent? An analysis of the UK biobank study. Journal of Bone and Mineral Research, 39 (4). pp. 399-407. ISSN 0884-0431

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Abstract

Whilst physical activity (PA) is recognised as a key bone mass determinant across life, athlete studies suggest that it may be less effective in women and older individuals. This has not been explored within the general population. We aimed to address this knowledge gap using data from the UK Biobank Study, a large population-based study of middle-aged and older adults. Free-living PA data collected at 100 Hz for seven days using wrist-worn accelerometers was classified as sedentary behaviour (0-29 milligravities (mg)), light (30-124 mg) or moderate-to-vigorous PA (125 + mg). Lumbar spine and femoral neck bone mineral density (BMD) was assessed using dual-energy X-ray absorptiometry. Associations between PA and BMD were assessed using linear regression models, with formal assessments of sex and age interactions undertaken and adjustments made for accelerometer wear time, height, body mass index, education, ethnicity, disability, and (in women only) menopausal status. In total, 15 133 UK Biobank participants (52% women) had complete PA, bone, and covariate data. In this sample, greater overall and moderate-to-vigorous PA was associated with higher lumbar spine BMD. In women these associations were typically weaker in older individuals, for example regression coefficients in women aged ≥70y ~50% were lower than at 45-54y (age-by- PA interactions p < 0.01 in all models). Similar associations were observed in basic but not full models for femoral neck BMD. Greater sedentary time was associated with lower lumbar spine BMD in men only, and greater light PA and sedentary time were associated with higher and lower femoral neck BMD respectively in both sexes. These results suggest that associations between PA and bone health at clinically-relevant sites are weaker in older than younger women. That positive associations are evident between overall and moderate-vigorous PA and femoral neck BMD even in women ≥70y suggests that PA for bone health should still be promoted in older women.