title: Associations between body mass index, lean and fat body mass and bone mineral density in middle-aged Australians: The Busselton Healthy Ageing Study.
abstract: Low BMI is a risk factor for osteoporosis, but it is not clear if relationships between BMI, lean mass (LM), fat mass (FM) and BMD are consistent across different levels of BMI. We studied 1929 Caucasian participants (1014 females) aged 45-66years in the Busselton Healthy Ageing Study in Western Australia. Body composition and BMD of total body, lumbar spine, total hip and femoral neck were measured using DXA. From generalized additive models, the positive relationships between BMI and BMD were weaker at high BMI, particularly at the spine and in males. In the entire cohort, adjusting for relevant covariates, LM and FM were significant predictors of all BMD measures in both genders. In men, analysis by tertiles of BMI showed that LM and FM (in kg) were positively associated with BMD (in mg/cm(2)) in tertile 1 except for LM and spine BMD (LM β: 5.18-6.80, FM β: 3.38-9.24, all P<0.05), but not in the middle or upper tertiles (LM β: -3.12-3.07, FM β: -4.75-1.82, P>0.05). In women, LM was positively associated with BMD in each tertile of BMI, except for spine BMD in the upper tertile, with regression coefficients lower in the upper tertile (β: 5.16-9.95, 5.76-9.56 and 2.80-5.78, respectively, all P<0.05). FM was positively associated with total body, spine and total hip BMD in women in BMI tertile 1 (β: 2.86-6.68, P<0.05); these associations were weaker or absent in the middle and upper tertiles. In conclusion, in middle-aged adults the positive relationships between lean or fat mass with BMD among those with higher BMI are absent in males and weaker in females.
authors: Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia; School of Medicine and Pharmacology, University of Western Australia, Crawley, Western Australia, Australia. Electronic address: kun.zhu@uwa.edu.au.
authors: Kun
authors: K
authors: Zhu
authors: Busselton Population Medical Research Institute, Busselton, Western Australia, Australia; School of Population Health, University of Western Australia, Crawley, Western Australia, Australia.
authors: Michael
authors: M
authors: Hunter
authors: School of Medicine and Pharmacology, University of Western Australia, Crawley, Western Australia, Australia; Department of Pulmonary Physiology and Sleep Medicine, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia.
authors: Alan
authors: A
authors: James
authors: Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia; Department of Clinical Biochemistry, PathWest Laboratory Medicine, Queen Elizabeth II Medical Centre, Nedlands, Western Australia, Australia.
authors: Ee Mun
authors: EM
authors: Lim
authors: Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia; School of Medicine and Pharmacology, University of Western Australia, Crawley, Western Australia, Australia.
authors: John P
authors: JP
authors: Walsh
mesh_terms: D050154:Adiposity; D000368:Aged; D000375:Aging; D000886:Anthropometry; D001315:Australia; D015992:Body Mass Index; D001835:Body Weight; D015519:Bone Density; D005260:Female; D005272:Femur Neck / Q000502:physiology; D006262:Health; D006615:Hip / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D013131:Spine / Q000502:physiology; D013851:Thinness / Q000503:physiopathology*
keywords: Body mass index; Bone mineral density; Busselton Healthy Ageing Study; Fat mass; Lean body mass; Middle-aged adults