i-PATHWAY: Development and validation of a prediction model for childhood obesity in an Australian prospective birth cohort.

Aim To develop and validate a model (i-PATHWAY) to predict childhood (age 8-9 years) overweight/obesity from infancy (age 12 months) using an Australian prospective birth cohort. Methods The Transparent Reporting of a multivariable Prediction model for individual Prognosis or Diagnosis (TRIPOD) checklist was followed. Participants were n = 1947 children (aged 8-9 years) from the Raine Study Gen2 - an Australian prospective birth cohort - who had complete anthropometric measurement data available at follow up. The primary outcome was childhood overweight or obesity (age 8-9 years), defined by age- and gender-specific cut-offs. Multiple imputation was performed to handle missing data. Predictors were selected using 2000 unique backward stepwise logistic regression models. Predictive performance was assessed via: calibration, discrimination and decision-threshold analysis. Internal validation of i-PATHWAY was conducted using bootstrapping (1000 repetitions) to adjust for optimism and improve reliability. A clinical model was developed to support relevance to practice. Results At age 8-9 years, 18.9% (n = 367) of children were classified with overweight or obesity. i-PATHWAY predictors included: weight change (0-1 year); maternal pre-pregnancy body mass index (BMI); paternal BMI; maternal smoking during pregnancy; premature birth; infant sleep patterns; and sex. After validation, predictive accuracy was acceptable: calibration slope = 0.956 (0.952-0.960), intercept = -0.052 (-0.063, -0.048), area under the curve = 0.737 (0.736-0.738), optimised sensitivity = 0.703(0.568-0.790), optimised specificity = 0.646 (0.571-0.986). The clinical model retained acceptable predictive accuracy without paternal BMI. Conclusions i-PATHWAY is a simple, valid and clinically relevant prediction model for childhood overweight/obesity. After further validation, this model can influence state and national health policy for overweight/obesity screening in the early years.