[Low bone mineral density in juvenile idiopathic arthritis: Prevalence and related factors].

INTRODUCTION

Height adjustment is currently recommended for Z-score bone mineral density (BMD) assessed by dual energy X-ray absorptiometry. At present there are no studies that evaluate the prevalence of low BMD in paediatric patients with Juvenile Idiopathic Arthritis (JIA) in Spain following current recommendations.

OBJECTIVES

To evaluate low BMD in JIA in paediatric patients with JIA in Spain following the latest recommendations, as well as to assess associated factors.

METHODS

Observational cross-sectional study of Spanish JIA patients from 5 to 16 years-old, followed-up in a Paediatric Rheumatology Unit between July 2014 and July 2015. Anthropometric, clinical and treatment data were recorded. Dual energy X-ray absorptiometry, and bone metabolism parameters were collected, and a completed diet and exercise questionnaire was obtained.

RESULTS

A total of 92 children participated. The population prevalence estimation of low BMD was less than 5% (95% CI). A significant positive correlation was found in the multiple linear regression analysis between the body mass index percentile (B: 0.021; P<.001) and lean mass index (B: 0.0002; P=.012), and BMD Z-score adjusted for height (Z-SAH). A significant negative correlation was found between fat mass index (B: -0.0001; P=.018) and serum type I collagen N-propeptide (B: -0,0006; P=.036) and Z-SAH.

CONCLUSIONS

Low BMD prevalence in JIA patients in our population is low. An adequate nutritional status and the prevalence of lean over fat mass seem to promote the acquisition of bone mass. Those JIA patients with lower BMD could be subjected to an increase of bone turnover.