Characterisation of Bone and Body Composition Parameters in Young Adults with Spina Bifida

Presentation Number: SAT 315
Date of Presentation: April 1st, 2017

Anne Trinh1, Phillip Wong1, Anuradha Sakthivel2, Michael Fahey3, Sabine Hennel4, Justin Brown3, Boyd J Strauss3, Peter R Ebeling3, Peter J Fuller1 and Frances Milat*1
1Hudson Institute of Medical Research, Clayton, Australia, 2Eastern Health, Australia, 3Monash University, Australia, 4Monash Health

Abstract

Context: Spina bifida (SB) can lead to marked changes in body composition and bone mineral density (BMD) through diminished ambulation, renal impairment and anticonvulsant medication use. With increased life expectancy, diseases of adulthood such as obesity and osteoporosis are emerging co-morbidities in SB, but there is limited literature to guide clinical management.

Objective: To examine the relationship between body composition, BMD, and fractures in adults with SB.

Design: Retrospective cross-sectional study.

Setting and Participants: 49 adults with SB (median age 32.7 years, interquartile range 22.6-39.0) who had dual-energy x-ray absorptiometry (DXA) imaging at a single tertiary hospital between 2004-2015.

Results: Despite the young age of the cohort, there was a high prevalence of metabolic comorbidities: obesity (79.6%), obstructive sleep apnoea (20.4%), hypertension (8.2%), deep vein thrombosis/pulmonary embolism (8.2%) and type 2 diabetes requiring medication (4.1%). The mean BMI was 31.7 ± 7.5 kg/m2, and BMI incorrectly classified 7 of 8 patients as normal who had an increased percentage total body fat on DXA. BMI was not statistically different between ambulatory and non-ambulatory patients (30.3 ± 6.8 kg/m2 vs 32.0 ± 8.7 kg/m2 respectively; p= 0.58). Using age and sex-matched fat centiles from NHANES III, 25 of 40 (62.5%) had total body percentage fat over the 95th centile as measured by DXA. Fat distribution was altered with leg and trunk fat increased to the 95th centile compared to the NHANES III population.

Low bone mass (defined as a Z score of ≤-2.0) was present in 21.9% of subjects at the L1 vertebra and in 35.1 % at the femoral neck (FN). Ten patients (20.4%) had a history of fragility fracture, all were of the femur and tibia apart from two fractures involving the shoulder. Fat mass accounted for 18.6% of the variance in BMD (p=0.005), which remained significant and positively associated with BMD after adjustment for age, gender and height. BMD or Z-score at L1, FN or total body site did not correlate with fracture.

Conclusions: Obesity and low BMD are common in young adults with SB. Changes in body composition seen in this cohort do not appear to be satisfactorily explained by ambulatory status. Strategies to improve BMI and body composition parameters are necessary to minimise comorbidities in this group.

 

Nothing to Disclose: AT, PW, AS, MF, SH, JB, BJS, PRE, PJF, FM