OBJECTIVES

: As childhood obesity increases, there is growing interest in the impact of Body Mass Index (BMI) upon bone health. This study investigated if there is an association between childhood BMI and fracture risk.

METHODS

: A prospective cohort of children with a valid primary care BMI measurement in Catalonia at age 4 years (±6 months) between 1/1/2001 and 31/12/2013 were identified in SIDIAP database, and followed up until they turned 15, migrated, died, or 31/12/2016.

Fractures were defined using validated ICD10 codes recorded in primary care. Childhood cumulative incidence (CI) (age 4 to 15 years) was calculated by anatomical location and stratified by BMI category (WHO 2007 growth reference). Cox models were used to estimate Hazard Ratios (HR) according to BMI.

RESULTS

: Of 466,997 children, 9250 (2.0%) were obese, 26526 (5.7%) overweight, and 540 (0.1%) underweight. We identified 20878 incident fractures. The CI of upper limb fracture for children with obesity was 76.1 per 10,000 (95%CI 58.4-81.1), compared to 62.1 (59.8-63.4) for normal weight. Lower limb fracture CI was 28.7 per 10,000 (18.0-34.1) in obesity and 15.1 (13.9-15.7) in normal weight.

Using BMI as a continuous variable, adjusted hazard ratios (HR; (95%CI)) were 1.05 (1.03-1.06) per 1 standard deviation increase for forearm fractures, 1.08 (1.05-1.12) for hand fractures, 1.14 (1.09-1.20) for ankle fractures and 1.15 (1.10-1.19) for foot fractures.

Divided by WHO categories, children with obesity had an adjusted HR (95%CI) of 1.14 (1.0-1.29) for forearm fractures, 1.37 (1.14-1.66) for hand fractures, 1.66 (1.32-2.10) for foot fractures and 1.81 (1.37-2.37) for ankle fractures. Further adjustment for birthweight (available for 310,751 children) did not affect these estimates.

CONCLUSIONS

: Childhood obesity is associated with a significantly increased risk of forearm, hand, ankle, and foot fractures. The effect of increased BMI upon fracture risk in adults appears to extend to the paediatric population.