Objective: Skeletal age deviation (SAD) is associated with bone mass and fracture risk in children but factors determining this are unknown. The aim of this population based cross-sectional study was to describe the factors associated with SAD.

Methods: A convenience sample of 640 male and female children aged 7–17 years was studied. All were assessed for body composition (DXA), diet, strength, dexterity, habitual physical activity, sunlight exposure, smoking and medication use. Skeletal age was assigned using the TW2 method.

Results: Subjects with a SAD >75^th percentile had significantly higher height, weight and Tanner stage compared to all other subjects. Bone free lean mass, fat mass and grip strength were positively associated with SAD. In multivariate analysis, ever smoking and use of inhaled corticosteroids were negatively associated with SAD while milk drinking was positively associated with SAD. There was no significant association between sunlight exposure, television watching, light or strenuous exercise and SAD.

Conclusions: The results of this study should be regarded as hypothesis generating but are biologically plausible and suggest that body composition, strength, diet, ever smoking and inhaled corticosteroid use may be determinants of bone maturity relative to age and thus affect fracture risk in children. However, further studies are necessary to explore other determinants of SAD such as genetic and perinatal factors and whether SAD influences peak bone mass.