THU0491 Factors associated with annual percentage changes in bone mineral density: a-14 years prospective population-based study
Authors: M.L. Marques, L. Brites, A. Marques, A. Daniel, M. Santiago, J.A. Pereira da Silva
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Gradual bone loss is expected with advancing age and gender differences were reported in the rate of annual loss of bone. Ideally, the decision to introduce interventions designed to prevent bone loss would be informed by reliable algorithms to identify fast bone losers. However, these are not readily available. <h3>Objectives</h3> In this analysis of 14 years prospective population-based data, we aim to identify predictors of the bone mineral density (BMD) loss in the perimenopausal and elderly population. <h3>Methods</h3> This study included members of the general population aged 40+years from the longitudinal cohort SAOL (individuals aged 18+years randomly selected from a local county of Coimbra, Portugal). The included individuals answered validated self-reported questionnaires at baseline (1997–2000) comprising questions on osteoporosis risk factors and medication use and underwent a Dual-energy x-ray absorptiometry (DXA) of the proximal femur (PF) and lumbar spine (LS). These procedures were repeated at follow-up (2011–2014). Demographic characteristics and DXA BMD details were descriptively summarised at baseline. Annual percentage changes of total BMD (g/cm<sup>2</sup>) in the PF and LS were computed (annual ΔBMD). The relationship between annual ΔBMD and potential predictors was assessed by independent-samples t-test or Pearson correlations, according to the categorical or continuous nature of the independent variable. The baseline independent variables included were: age (years); gender; body mass index (kg/m<sup>2</sup>); smoking, alcohol intake, rheumatoid arthritis, glucocorticoid treatment and secondary osteoporosis according to FRAX algorithm definitions. The follow-up reported calcium/vitamin D supplementation and treatment with bisphosphonates, for at least 1 year (yes/no), were also considered as independent variables. We used linear regression models (enter method) to estimate the possible association between socio-demographic/clinical variables and the BMD changes of PF and LS. The predictor variables included in the model were selected <i>a priori</i> based on variables that were associated with annual ΔBMD on univariate analysis. Results were considered significant when p&lt;0.05. <h3>Results</h3> This analysis included data from 636 individuals (mean (±SD) age of 53±8 years,76% female). The mean (±SD) follow-up period was 13.6±1.1 years. Baseline mean (±SD) BMD of the PF and LS were 0.77±0.004 and 0.94±0.132, respectively. The mean (±SD) percentage of annual bone loss was: −0.19±1.02 for PF and −0.06±0.84 for LS. On univariate analysis, ΔBMD at both the PF and LS was significantly associated with gender (p&lt;0.001). Annual Δ BMD was also associated with vitamin D supplements (p=0.014) at PF, and with calcium supplements (p=0.002) and bisphosphonate treatment (p=0.027) at LS. On multiple linear regression analysis, female gender persisted as a predictor of faster BMD loss in both PF (p≤0.001) and LS (p=0.006). While bisphosphonate treatment didn't predict the annual bone loss, vitamin D and calcium supplementation persisted as predictors of lower annual ΔBMD at PF (p=0.034) and LS (p=0.033), respectively. <h3>Conclusions</h3> Our results confirm that the rate of BMD loss at PF and LS over 14 years is significantly associated with gender. Vitamin D and calcium supplementation appeared to have a role in the prevention of bone loss in this general population cohort. <h3>Disclosure of Interest</h3> None declared