Background: Altered body composition and poor bone health is common in children with cerebral palsy (CP). Muscle development plays an integral part of bone mass accrual in the growing skeleton, with childhood being a critical time to achieve optimal peak bone mass.
Aim: To explore the associations between body composition, bone mineral content (BMC), and areal bone mineral density (aBMD) in children with CP.
Method: Dual-energy X-ray absorptiometry (DXA) was used to assess total body BMC, aBMD, fat free mass (FFM), bone free fat free mass (BFFFM, proxy for muscle mass) and fat mass (FM) in 18 children with CP (11M), age 5.3 ± 0.7 years, with Gross Motor Classification: 1=7, II=4, III=3, IV=2, V=2. Height and weight were measured to the nearest millimetre and 100grams, and converted to Z-scores. The indices FFM/height2 (FFMI) and FM/height2 (FMI) were calculated.
Results: BMC correlated positively with: BFFFM (r=0.83, p<0.01); height Z-score (r=0.80, p<0.01) and weight Z-score (r=0.57, p<0.05). FMI had significant positive correlations with weight (r=0.61, p<0.01) and BMI Z-scores (r=0.67, p<0.01), but not height Z-score (r=0.11, ns). Though not significant, aBMD Z-score correlated negatively with FMI (r=-0.34, ns) and positively with FFMI (r=0.26, ns).
Conclusion: These results show increased BMC is strongly associated with increased BFFFM. Interestingly, lower aBMD Z-score tended to be associated with higher FMI. These data may suggest a greater influence on BMC may arise from muscle forces on bone rather than body weight, whereas increasing fat mass tends to have a negative effect on bone. Further investigation of body composition in young children with CP is warranted to ensure optimal bone mass accrual in childhood.