SUN-737 - Associations between Waist Measures and Bone Mineral Density: The ELSA-Brasil Cohort

INTRODUCTION
It is widely recognized that body mass index (BMI) is positively associated with bone mineral density (BMD). However, studies assessing waist measurements, such as waist circumference (WC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR) and their association with BMD are inconsistent. Although visceral adipose tissue may benefit bone by expression of aromatase and through mechanical loading, it may negatively impact bone through production of proinflammatory molecules.
We hypothesized that waist measurements would be inversely associated with BMD.

METHODS
We analyzed 1,316 individuals from the ELSA-Brasil cohort who had a DXA. The associations between WC, WHR, and WHtR with BMD at the hip, femoral neck, and spine (L1-L4) were examined by univariate linear regression and pairwise Pearson correlation followed by multivariable linear regression adjusted for age, sex, race, BMI, tobacco use, alcohol use, and physical activity. Further analyses were performed with stratification by sex, adding age of menarche, number of pregnancies and current or previous use of hormonal contraceptive for females. p< 0.05 was considered statistically significant.

RESULTS
Mean age was 58 ± 8.5 years; 59.2% were White, with mean BMI of 28.3 kg/m2. Females represented 61.2% of participants (51.4% were postmenopausal).
All waist measures were positively associated with BMD in univariate regression and correlation analyses (r: 0.15 - 0.40, p < 0.001 for all measures at all sites). In the adjusted model, WC was no longer associated with BMD at all 3 sites (p ≥ 0.6), while WHR was negatively associated with BMD at the femoral neck (p=0.005) and no longer associated with BMD at the hip or spine; WHtR was negatively associated with BMD at all 3 sites (p ≤ 0.002 for all).
After sex stratification, univariate analyses showed positive associations of WC and WHtR with BMD in both sexes at all sites (p ≤ 0.002 for all); while WHR was only positively associated with hip BMD in females (p ≤ 0.001). In the adjusted model, WC was no longer associated with BMD in either sex (p ≥ 0.27). WHR showed no associations with BMD in females and in males it was negatively associated with spine (p=0.03) and femoral neck BMD (p=0.04), with no association at the hip. WHtR was negatively associated with BMD at all sites in males (p ≤ 0.013) and at the femoral neck (p=0.004) and spine (p=0.009) in females.

DISCUSSION
Waist measures showed positive associations with BMD in univariate models, but these became null or inverse associations after adjustment for confounders, suggesting that visceral fat has an overall negative effect on BMD; WHtR was the most consistent waist measure associated with BMD. Caution should be taken in interpreting studies assessing waist measurements and BMD if potential confounders are not taken into account.

*Unless otherwise noted, all abstracts presented at ENDO must not be released to the press or the public until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.*