Maturitas 74 (2013) 264–269 Contents lists available at SciVerse ScienceDirect Maturitas jo ur n al hom ep age : www.elsevier.com/locate/maturitas Lean soft tissue contributes more to bone health than fat mass independent of physical activity in women across the lifespan Gunnhildur Hinriksdóttir a,∗ , Sigurbjörn Á. Arngrímsson a , Mark M. Misic b , Ellen M. Evans c a Center for Sport and Health Sciences, University of Iceland, Lindarbraut 4, 840 Laugarvatn, Iceland b Department of Kinesiology and Physical Education, Northern Illinois University, DeKalb, IL 60115 USA c Department of Kinesiology, 101A Ramsey Center, 300 River Road, University of Georgia, Athens, GA 30602 USA a r t i c l e i n f o Article history: Received 10 July 2012 Received in revised form 3 December 2012 Accepted 17 December 2012 Keywords: Bone density Lean soft tissue Fat mass Pedometer Women a b s t r a c t Objectives: To investigate the association between lean soft tissue (LST) and fat mass (FM) on bone health variables in women across the lifespan, while taking into account the influence of objectively measured habitual physical activity (PA). Study design: A total of 104 women, 37 young (23.3 ± 2.6 years), 28 middle-age (49.2 ± 5.4 years), and 39 old (68.3 ± 6.4 years) participated in this cross-sectional study. All underwent a DXA scan and wore a pedometer for 7 days. Main outcome measures: Bone mineral content (BMC) and BMD of the whole body (WB), lumbar spine (LS) and proximal femur (PF), and body composition (FM and LST) were assessed with DXA and PA (steps/day) was assessed from 7 day pedometer counts. Results: LST was significantly and positively associated with PF and LS BMD (r = 0.34; 0.67, p < 0.05), and WB, PF and LS BMC (r range = 0.41–0.59, p < 0.05) in all age groups and WB BMD in the middle-age group (r = 0.72, p < 0.05) independent of PA, FM, and hormonal status. FM was not positively associated with any bone variable in any age group when adjusted for PA, LST, and hormonal status. PA was significantly asso- ciated with WB BMD in the middle-age group (r = 0.60, p < 0.05), independent of LST, FM, and hormonal status. Conclusions: LST contributes more to bone health in women across the lifespan than FM, independent of PA and hormonal status. © 2013 Elsevier Ireland Ltd. All rights reserved. 1. Introduction Body weight, body composition, and physical activity (PA) have all been implicated as determinants of bone mineral density (BMD). It is well established that body weight is one of the main determinants of BMD in both pre- and postmenopausal women [1]. Postmenopausal women with low body mass index (BMI) (<19 kg/m 2 ) are at a significantly greater risk for osteoporosis than normal weight women, and as BMI increases, the risk for osteoporo- sis decreases [2]. Similarly, PA plays a major role in maximizing and maintaining bone mass during childhood and into adulthood and minimizing the loss as we age [3]. The association between body composition (i.e. fat and lean mass) and bone mineral content (BMC) and BMD is, however, not as conclusive and continues to be of debate. Generally, lean soft tissue (LST) appears to be a greater predictor of BMD [4–8] and ∗ Corresponding author. Tel.: +354 525 5313; fax: +354 481 3910; mobile: 354 694 5244. E-mail address: ghinriks@hi.is (G. Hinriksdóttir). BMC [9] than fat mass (FM) in pre- and perimenopausal women, although the opposite has also been reported [10,11]. Studies on postmenopausal women are equivocal regarding the association between LST, FM and BMD and/or BMC as some have reported a greater influence of FM [10,12–14], whereas other have reported a greater influence of LST [4,6,9,15–17], although FM appears to become more important with advancing age [4,6,7]. Further- more, changes in FM appear to be more important for BMD than changes in LST in postmenopausal women [17], whereas changes in LST appear more important in younger post- and premenopausal women [18]. It is well known that habitual PA has favorable effects on body composition and is associated with reduced weight and body fat mass [19]. Despite this, only limited literature in this area [4,10,14,15,20] has considered the influence of PA on bone health, however, the authors did not include PA in their analysis as PA was not associated with the bone health measures. PA could, in fact, contribute to the discrepancy in the association of LST, FM and bone health variables as a confounder because LST, but not FM, has been reported as a significant predictor of BMD in phys- ically active pre- and postmenopausal women whereas FM and 0378-5122/$ – see front matter © 2013 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.maturitas.2012.12.009