Prevalence of overweight among school children in Hannover region from 2010 to 2014: A comparison between four body mass index references

 

Background:

The age-specific body mass index (BMI) is the most widely used tool for monitoring childhood overweight. However, different BMI classification reference systems imply obstacles for comparisons. In Germany, two national references are currently used: the Kromeyer-Hauschild (KH) and the KIGGS reference. This study aims to test the agreement within these two national and two international classification systems.

Methods:

Using data from the school entrance examination in the Hannover Region from 2010 to 2014 (n = 51,520), children“s weight status was classified according to different reference systems: KH, KiGGS, the International Obesity Task Force (IOTF) reference and the WHO reference. The BMI value of overweight status was divided into two categories (pre-obesity and obesity). Cohen“s kappa coefficient (k) was calculated to assess the degree of agreement of the four classification systems.

Results:

The prevalence of overweight was highest with the WHO references (17.5%, 95% CI 17.2 – 17.8) in comparison to the KH (9.3%, 95% CI 9.0 – 9.5), KIGGS (9.0%, 95% CI 8.8 – 9.3) and the IOTF references (12.3%, 95% CI 12.0 – 12.6). Kappa coefficients were higher between the obese category (0.75 ≤ κ ≤0.96; p < 0.001) compared to the pre-obese category (0.61 ≤ κ ≤0.94; p < 0.001). Agreement between the two national references achieved „nearly perfect agreement“ (κ= 0.98; p < 0.001).

Conclusion:

The WHO reference produced a higher prevalence in overweight compared to the other references. Since there are only minor differences between KiGGS and KH reference, we suggest that using both references to define BMI is acceptable and will not produce distorted results.