Overweight and obesity prevalence in children based on 6- or 12-month IOTF cut-points: does interval size matter?

Area of Science:

• Pediatrics
• Public Health
• Epidemiology

Background:

• The International Obesity Taskforce (IOTF) provides age- and gender-specific body mass index (BMI) cut-points for defining childhood overweight and obesity.
• These cut-points are available in 6- and 12-month age intervals.
• Nonlinear BMI-for-age curves can introduce bias when using wider age intervals.

Purpose of the Study:

• To quantify the bias in overweight and obesity prevalence estimates introduced by using 12-month versus 6-month age intervals for IOTF cut-points.
• To assess the age-dependency of this bias in Australian children.

Main Methods:

• Analysis of body mass index (BMI) data from 2178 Australian children aged 4-12 years.
• Comparison of prevalence estimates for overweight and obesity using 6-month versus 12-month age intervals based on IOTF criteria.
• Assessment of bias across different age groups.

Main Results:

• Using 12-month intervals underestimated overall overweight and obesity prevalence by 1.4% compared to 6-month intervals.
• The bias was age-dependent: overestimation in 4-year-olds and underestimation (up to 2.6%) in older children.
• Overweight prevalence was more affected by the interval difference than obesity prevalence.

Conclusions:

• The choice of age interval (6- vs. 12-month) for IOTF BMI cut-points introduces a small but systematic bias in childhood overweight and obesity prevalence estimates.
• This bias is age-dependent, impacting prevalence figures differently across pediatric age groups.
• Accurate prevalence estimation requires careful consideration of age interval selection in applying IOTF guidelines.