Fitness, fatness and activity as predictors of bone mineral density in older persons.
OBJECTIVE
To determine relationships of bone mineral density (BMD) with fitness, physical activity, and body composition and fat distribution.


METHODS
Cross-sectional.


METHODS
General Clinical Research Center, Johns Hopkins Bayview Medical Center, Baltimore, Maryland.


METHODS
Men (n = 38) and women (n = 46), aged 55-75 years with high normal blood pressure or mild hypertension but otherwise healthy.


METHODS
Aerobic fitness (oxygen uptake) on a treadmill, muscle strength by one-repetition maximum, activity by questionnaire, abdominal obesity by magnetic resonance imaging; anthropometrics, and body composition by dual energy X-ray absorptiometry (DXA) which measured total fat and lean mass, and BMD for the total skeleton, lumbar spine (L1-L4) and total hip.


RESULTS
Aerobic fitness did not correlate with BMD. Using multivariate analysis to ascertain independent contributions to the variance in BMD, in women, with adjustment for hormone replacement therapy (HRT), total skeleton BMD was independently related to muscle strength and abdominal total fat; total hip BMD to body weight; lumbar spine BMD to abdominal total fat. HRT also influenced BMD in the lumbar spine. In men, lumbar spine BMD was independently related to abdominal total fat physical activity and total hip BMD related to lower body strength. P < 0.05 for all of these correlations.


CONCLUSIONS
Abdominal obesity and muscle strength emerge as predominant correlates of BMD in older persons with stronger relationships seen in women. Body weight and HRT also explained portions of the variance in BMD in women. Whether abdominal obesity is simply a marker for general obesity or has independent protective effects on bone is yet to be determined.
Stewart
K J
KJ
Department of Medicine, Division of Cardiology, Johns Hopkins Bayview Medical Center, Johns Hopkins University, School of Medicine, Baltimore, MD 21224, USA. kstewart@mail.jhmi.edu
Deregis
J R
JR
Turner
K L
KL
Bacher
A C
AC
Sung
J
J
Hees
P S
PS
Tayback
M
M
Ouyang
P
P
D000005:Abdomen; D015502:Absorptiometry, Photon / Q000379:methods; D000273:Adipose Tissue / Q000502:physiology*; D000368:Aged; D001823:Body Composition / Q000502:physiology*; D015519:Bone Density / Q000187:drug effects*; D003430:Cross-Sectional Studies; D005260:Female; D020249:Hormone Replacement Therapy / Q000379:methods; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000503:physiopathology; D010809:Physical Fitness / Q000502:physiology*; D012307:Risk Factors