Physical Activity Associations With Bone Mineral Density and Modification by Metabolic Traits

Anshu Buttan; Jinrui Cui; Xiuqing Guo; Yii-Der I. Chen; Willa A. Hsueh; Jerome I. Rotter; Mark O. Goodarzi

Disclosures

J Endo Soc. 2020;4(8) 

In This Article

Abstract and Introduction

Abstract

Objective: To assess the relationship of physical activity with bone mineral density (BMD) at various sites and examine potential modifying metabolic factors.

Methods: Responses from physical activity questionnaires were used to determine total physical activity (PA), moderate physical activity (mod-PA), and sedentary time. Regression analyses were performed to evaluate association of activity traits with insulin sensitivity by euglycemic clamp, adiponectin, C-reactive protein (CRP), and plasminogen activator inhibitor-1 (PAI-1) in 741 healthy subjects.

Results: The cohort was relatively sedentary. Activity level was associated with arm, pelvis, and leg BMD in univariate analyses. In multivariate association analyses of arm BMD, only female sex (β = -0.73, P < 0.0001) and adiponectin (β = -0.076, P = 0.0091) were significant. Multivariate analyses of pelvis BMD found independent associations with body mass index (BMI) (β = 0.33, P < 0.0001), adiponectin (β = -0.10, P = 0.013), female sex (β = -0.18, P < 0.0001), sedentary time (β = -0.088, P = 0.034), PA (β = 0.11, P = 0.01), and mod-PA (β = 0.11, P = 0.014). Age (β = -0.10, P = 0.0087), female sex (β = -0.63, P < 0.0001), BMI (β = 0.24, P < 0.0001), and mod-PA (β = 0.10, P = 0.0024) were independently associated with leg BMD.

Conclusions: These results suggest that BMD increases with physical activity in the arms, legs, and pelvis and is inversely related to sedentary time in the pelvis and legs; these associations may be modified by age, sex, BMI, and adiponectin, depending on the site, with physical activity being more important to pelvis and leg BMD than arm BMD and sedentary time being important for pelvis BMD. Moreover, we demonstrated that CRP, PAI-1, and insulin sensitivity play a minor role in BMD.

Introduction

Physical activity is known to play a significant role in bone mineral density (BMD). Multiple studies have shown positive correlations between both resistance and aerobic training exercise with improved BMD.[1–4] In a meta-analysis of 32 randomized clinical control trials, both premenopausal and postmenopausal women demonstrated improved lumbar spine BMD in aerobic and resistance training groups.[5] Data also suggest that increased activity level in young women and minimizing sedentary behavior in older women are independently associated with improved lumbar spine and femoral neck BMD across a woman's lifespan.[6] Others have reported positive effects on BMD of increased activity level and reduced sedentary time in both men and women.[7,8] Screen-based sedentary time has been noted to have a particularly deleterious impact on BMD.[8]

Moreover, seemingly disparate activities, sports, and exercise regimens have demonstrated improved BMD.[9–11] One study noted improved BMD in both men and women with swimming, a nonimpact sport, over a 9-month follow-up period, though prolonged periods of engagement appeared to negatively affect these gains, independent of sex.[11] Basketball, karate, judo, ballet, and water polo have also all demonstrated improved BMD compared with control.[9,10,12] The benefits of exercise on BMD have even been seen in the context of weight loss.[13,14]

Interestingly, serum osteoprotegerin and receptor activator of nuclear factor kappa B ligand levels have not shown significant change in response to exercise, which may suggest alternative metabolic pathways mediating effects of exercise on BMD.[15] Exercise has been independently associated with changes in metabolic markers such as C-reactive protein (CRP), plasminogen activator inhibitor-1 (PAI-1), insulin sensitivity, and adiponectin.[16–19] Increased physical activity and reduced sedentary time have been shown to reduce CRP levels.[20,21] Several studies have also shown similar associations between PAI-1 and exercise, whereas increases in adiponectin and improved insulin sensitivity have been associated with exercise.[22–26]

However, data are currently limited regarding whether metabolic parameters such as CRP, PAI-1, insulin sensitivity, and adiponectin may modulate the effects of physical activity on BMD. Gaining a better understanding of this potential link may prove valuable in the context of clinical practice, counseling patients, and improving bone health. Our aim was to establish the relationship of physical activity level with BMD assessed by dual energy x-ray absorptiometry (DXA) and determine whether metabolic traits modify or mediate associations between physical activity and BMD.

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