Background: Childhood obesity is associated with an increased risk of adult obesity and related chronic disease. Our aim was to identify modifiable exposures that are independently associated with obesity in the preschool age group. Methods: A prospective cohort study of 5734 children in New Zealand with anthropometric measurements was completed at age 4.5 years. The modifiable exposures of interest, measured at age 9 months and 2 years, were: food security during infancy; and, at age 2 years, screen time; sleep duration; and takeaway food and soft drink intake. The risk of obesity independently associated with each exposure was determined using Binomial and Poisson regression and described using adjusted risk ratios (RRs) and 95% confidence intervals (CIs), after controlling for confounding variables including gender, ethnicity, birth weight, and mother's age. The probability of obesity given cumulative exposures to the four risk factors and the population attributable fraction (PAF) were estimated. Results: Lower food security during infancy (<mean study sample score; RR = 1.32; 95% CI : 1.06-1.64) and, at age 2 years, more screen time (>1 hour/day; RR = 1.22; 95% CI : 1.01-1.48), shorter sleep duration (≤11.5 hours/day; RR = 1.30; 95% CI : 1.05-1.61), and weekly to daily consumption of takeaway/soft drink (RR = 1.25, 95% CI : 1.00-1.57) were independently associated with an increased risk of obesity at age 4.5 years. The cumulative PAF for childhood obesity was 42.9%, under an ideal scenario where all risk factors were eliminated. Conclusion: Exposure to modifiable factors by age 2 years is associated with obesity at age 4.5 years. Interventions to prevent childhood obesity need to be effective during infancy.
Keywords: early childhood; modifiable risk factors; obesity.