Association between body mass index and osteoporosis in women from northwestern Rio Grande do Sul.

OBJECTIVE: To investigate the association between body mass index (BMI) and bone mineral density (BMD) in postmenopausal women.

METHODS: Observational study with postmenopausal women who underwent bone densitometry in Palmeira das Missões - RS. Sociodemographic data, risk for osteoporosis and food intake were assessed through a specific form. BMI was calculated according to WHO criteria. The assessment of BMD was performed by Dual-energy X-ray absorptiometry (DXA) and classified according to WHO. Statistical analysis was performed using prevalence ratios (PR) and their respective 95% confidence intervals for the factors studied. Variables associated with p<0.20 with the different outcomes (osteopenia and osteoporosis) were included in a Poisson regression model with robust variance to adjust for potential confounding factors. A 5% significance level was considered.

RESULTS: 393 postmenopausal women with a mean age of 59.6±8.2 years participated. After the adjustments, the normal weight women had 1.2 times the prevalence of osteopenia of obese women (PR=1.2; CI 95% 1.3-1.5). Considering osteoporosis, the PR of euthophic women was twice the PR of obese women (PR=2; CI 95% 1.4-2.9) and was 1.7 times greater for overweight group compared to obese category (PR=1.7; CI 95% 1.2-2.5).

CONCLUSION: Obese women had lower prevalence of osteopenia compared with normal weight subjects and also with lower prevalence of osteoporosis as compared to normal- and overweight women.