Endocrine Abstracts

Aims: To examine, in children with Osteogenesis Imperfecta (OI): the prevalence of overweight and obesity, longitudinal trends in body mass index (BMI) z-scores and total body fat percentage (TBF) assessed on dual-energy X-ray absorptiometry (DXA) scans, correlation between BMI and TBF and fractures and BMI z-score.

Methods: Retrospective cross-sectional and longitudinal analysis of children with OI, with minimum 5 years data on DXA scans, at a single nationally commissioned OI service. Data was gathered on severity of OI, number of fractures (long bone and vertebral) during study period, BMI, BMI z-scores and TBF. Obesity and overweight were defined in accordance with the UK-WHO growth standard criteria. The cohort was categorised into pre-pubertal (6-8 years), pubertal (9-14 years) and post-pubertal (15-18 years). A t-test and Kruskall-Wallis test was used to compare groups and categories respectively. Pearson’s test was used to assess correlations.

Results: A total of 54 patients (55.6%, n=30 males) were included. The majority (n=44, 81.5%) had mild OI (G1) and rest moderate/severe (G2) (n=10,18.5%). 25.9% (n=14) were obese and 33.3% (n=18) overweight. In G1 and G2 the prevalence of obesity was 27.3% and 20% respectively and of overweight was 27.3% and 60% respectively. The mean BMI z-score at baseline (mean age 8.4 years) in G1 and G2 was (+0.49 and +1.02 respectively; P>0.05) similar. At the most recent visit (mean age 14.2 years) the mean BMI z-score was higher in G2 compared to G1 (+1.92 vs +1.06 respectively; P=0.04). The pre-pubertal, pubertal, and post-pubertal mean BMI z-scores were +0.33, +1.03 and +1.5 respectively (p<0.001) and mean TBF were 30.9%, 36.0% and 38% respectively (p<0.001). There was a significant correlation between BMI and TBF (r=0.813, P= <0.001). The BMI z-score was significantly correlated to the number of long bone fractures (r=0.28, p<0.001) but not vertebral fractures (P=0.6).

Conclusion: Children with moderate/sever OI had a higher BMI in the post-pubertal years and this tendency was correlated to long bone fracture rate. Awareness of risk factors provides the opportunity to intervene early. Monitoring TBF on DXA scans is useful when clinical assessment of BMI is challenging.