title: Changes in bone mineral density over time by body mass index in the health ABC study.
abstract: Obesity appears protective against osteoporosis in cross-sectional studies. However, results from this longitudinal study found that obesity was associated with bone loss over time. Findings underscore the importance of looking at the longitudinal relationship, particularly given the increasing prevalence and duration of obesity among older adults.
  
  
  
  Cross-sectional studies have found a positive association between body mass index (BMI) and bone mineral density (BMD), but little is known about the longitudinal relationship in US older adults.
  
  
  
  We examined average annual rate of change in BMD by baseline BMI in the Health, Aging, and Body Composition Study. Repeated measurement of BMD was performed with dual-energy X-ray absorptiometry (DXA) at baseline and years 3, 5, 6, 8, and 10. Multivariate generalized estimating equations were used to predict mean BMD (femoral neck, total hip, and whole body) by baseline BMI (excluding underweight), adjusting for covariates.
  
  
  
  In the sample (n = 2570), 43 % were overweight and 24 % were obese with a mean baseline femoral neck BMD of 0.743 g/cm(2), hip BMD of 0.888 g/cm(2), and whole-body BMD of 1.09 g/cm(2). Change in total hip or whole-body BMD over time did not vary by BMI groups. However, obese older adults lost 0.003 g/cm(2) of femoral neck BMD per year more compared with normal weight older adults (p < 0.001). Femoral neck BMD change over time did not differ between the overweight and normal weight BMI groups (p = 0.74). In year 10, adjusted femoral neck BMD ranged from 0.696 g/cm(2) among obese, 0.709 g/cm(2) among normal weight, and 0.719 g/cm(2) among overweight older adults.
  
  
  
  Findings underscore the importance of looking at the longitudinal relationship between body composition and bone mineral density among older adults, indicating that high body mass may not be protective for bone loss over time.
authors: Centers for Medicare and Medicaid Services, 7500 Security Blvd, WB-06-05, Baltimore, MD, 21244, USA. Jennifer.Lloyd@cms.hhs.gov.
authors: J T
authors: JT
authors: Lloyd
authors: Centers for Medicare and Medicaid Services, 7500 Security Blvd, WB-06-05, Baltimore, MD, 21244, USA.|Department of Epidemiology and Public Health, University of Maryland, Baltimore, MD, USA.
authors: D E
authors: DE
authors: Alley
authors: Department of Epidemiology and Public Health, University of Maryland, Baltimore, MD, USA.
authors: M C
authors: MC
authors: Hochberg
authors: Doctoral Program in Gerontology, University of Maryland, Baltimore and Baltimore County, Baltimore, MD, USA.|Department of Psychology, University of Maryland, Baltimore County, Baltimore, MD, USA.
authors: S R
authors: SR
authors: Waldstein
authors: Laboratory of Epidemiology and Population Sciences, Intramural Research Program, National Institute on Aging, Bethesda, MD, USA.
authors: T B
authors: TB
authors: Harris
authors: Sticht Center on Aging, Wake Forest School of Medicine, Winston-Salem, NC, USA.
authors: S B
authors: SB
authors: Kritchevsky
authors: Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, USA.
authors: A V
authors: AV
authors: Schwartz
authors: Department of Epidemiology, Graduate School of Public Health University of Pittsburgh, Pittsburgh, PA, USA.
authors: E S
authors: ES
authors: Strotmeyer
authors: University of Tennessee Health Science Center, Memphis, TN, USA.
authors: C
authors: C
authors: Womack
authors: Department of Epidemiology and Public Health, University of Maryland, Baltimore, MD, USA.|Doctoral Program in Gerontology, University of Maryland, Baltimore and Baltimore County, Baltimore, MD, USA.
authors: D L
authors: DL
authors: Orwig
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D015992:Body Mass Index; D015519:Bone Density; D003430:Cross-Sectional Studies; D005260:Female; D006306:Health Surveys; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D013997:Time Factors
keywords: Aging; Longitudinal; Obesity; Osteoporosis