The association between body mass index and osteoporosis in patients referred for a bone mineral density examination.
OBJECTIVE
Osteoporosis affects 4-6 million (13%-18%) postmenopausal white women in the United States. Most studies to date on risk factors for osteoporosis have considered body mass index (BMI) only as a possible confounder. In this study, we assess the direct relationship between BMI and osteoporosis.


METHODS
We conducted a cross-sectional study among women aged 50-84 years referred by their physicians for a bone mineral density (BMD) examination at Baystate Medical Center between October 1998 and September 2000. BMI was determined prior to the BMD examination in the clinic. Information on other risk factors was obtained through a mailed questionnaire. Ordinal logistic regression was used to model the association between BMI and osteoporosis, controlling for confounding factors.


RESULTS
BMI was inversely associated with BMD status. After adjustment for age, prior hormone replacement therapy (HRT) use, and other factors, odds ratios (OR) for low, high, and obese compared with moderate BMI women were 1.8 (95% CI 1.2-2.7), 0.46 (95% CI 0.29- 0.71), and 0.22 (95% CI 0.14-0.36), respectively, with a significant linear trend (p < 0.0001) across BMI categories. Evaluating BMI as a continuous variable, the odds of bone loss decreased 12% for each unit increase in BMI (OR = 0.88, 95% CI 0.85-0.91).


CONCLUSIONS
Women with low BMI are at increased risk of osteoporosis. The change in risk associated with a 1 unit change in BMI ( approximately 5-8 lb) is of greater magnitude than most other modifiable risk factors. To help reduce the risk of osteoporosis, patients should be advised to maintain a normal weight.
Asomaning
Kofi
K
Harvard School of Public Health, Boston, Massachusetts 02115, USA. kasomani@hsph.harvard.edu
Bertone-Johnson
Elizabeth R
ER
Nasca
Philip C
PC
Hooven
Frederick
F
Pekow
Penelope S
PS
D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D015519:Bone Density; D016001:Confidence Intervals; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008875:Middle Aged; D016017:Odds Ratio; D015663:Osteoporosis, Postmenopausal / Q000453:epidemiology / Q000209:etiology*; D012307:Risk Factors; D013851:Thinness / Q000150:complications* / Q000453:epidemiology; D014481:United States / Q000453:epidemiology; D016387:Women's Health