21815
Bone Accrual in Boys with Autism Spectrum Disorder
Objectives: Our objective was to prospectively assess bone accrual over a four-year period in adolescent males with ASD compared to TDC during the critical adolescent years when bone accrual rates are at their highest.
Methods: 36 males (19 ASD, 17 TDC) were enrolled at study initiation. Over four years, eleven participants (5 ASD, 6 TDC) were lost to follow-up. Thirteen participants (6 ASD, 7 TDC) were subsequently added for the follow-up visit to total 25 ASD, 24 TDC, (10.8± 1.7y and 11.7± 1.9y respectively). BMD was measured at the hip and lumbar spine using dual-energy X-ray absorptiometry (DXA) in 2011 and 2015. In 2015, whole body BMD was also measured for returning and new participants. BMD Z-scores were calculated using Hologic pediatric databases. We collected the medical history, activity questionnaires, food records, and fasting calcium, phosphorus, and 25(OH) vitamin D levels. Bone accrual rates were calculated for 14 ASD (10.8± 1.7y at baseline and 14.71± 1.7y at follow up) and 11 TDC (11.2± 1.5y at baseline and 15.2± 1.6y at follow up) who participated at both time points. Data are represented as mean (SE).
Results: Tanner stage, BMI z-scores, height z-scores and, serum vitamin D and calcium did not differ between groups at baseline and follow up. Boys with ASD had lower BMD Z scores than controls at (i) the lumbar spine at baseline [-1.01(0.23) vs. -0.14(0.24), P < 0.009] and follow-up [-1.16(0.31) vs. -0.17(0.35), P < 0.04], (ii) the total hip at baseline [-0.69(0.28) vs. 0.04(0.23), P < 0.025] and follow-up [-1.27(0.32) vs. -0.18(0.36), P <0.027] and (iii) femoral neck at baseline [-1.57(0.18) vs -0.51(0.18), P <0.001] and follow-up [-1.52(0.29) vs. -0.32(0.33), P < 0.009], and for the whole body less head at the follow-up visit [-1.25(95% CI -1.68, -0.82) vs. -0.48(95% CI -0.91, -006)]. Bone accrual rates did not differ between ASD and TDC at any site. Vitamin D intake from food was lower in ASD vs. TDC at baseline [5.09(0.99) vs. 9.27(1.01) mcg/day, P < 0.006], but not at follow-up. Calcium intake at baseline and follow-up did not differ between groups. In addition, a lower proportion of ASD vs. TDC were categorized as being “very physically active” at both baseline (16% vs. 75%, P < 0.001) and follow-up (14.7% vs. 74.8%, P < 0.01).
Conclusions: This is the first study to prospectively examine BMD in adolescent boys with ASD compared with controls. Participants with ASD continued to have lower BMD during adolescence compared to controls, but bone accrual (change in BMD over time) did not differ between groups. Further studies are needed to (i) evaluate the long-term consequences of decreased BMD in ASD, (ii) evaluate BMD in females and adults with ASD, and (iii) assess the effect of interventions to improve BMD in individuals with ASD.