Waist circumference and waist-to-height ratio percentiles in a nationally representative sample of 6-13 year old children in Switzerland.

OBJECTIVES Central obesity, measured as waist circumference (WC), is an important risk factor for cardiovascular disease and diabetes already in children. The ratio of waist circumference to height (WHtR) is a further indicator for body shape. International reference values, however, do not exist for any of the two measures and neither do references specific to Switzerland. The aim of this study therefore was to develop WC and WHtR percentiles from a nationally representative sample of Swiss children. METHODS In a nationally representative sample of 2,303 6 to 13 year old children in Switzerland weight, height and WC were measured and body fat % (%BF) was determined from multiple skinfold-thickness measurements. WC, WHtR and % BF percentiles were calculated using the LMS-Method of Cole and Green. RESULTS WC increases almost linearly over the age range of 6 to 13 years for both boys and girls. Generally, girls show slightly lower WC than boys, but in the higher percentiles (85th, 90th and 95th) they reach the same or even slightly higher values around 10 years of age. At the 85th percentile for boys and the 90th percentile for girls, WHtR remains constant over the entire age range. Above these levels the ratio increases and below it decreases with age. Percentiles for %BF in boys increase constantly up to an age of 11.5 years, after which they plateau. For girls, the plateau can be seen earlier, around 10.5 years, but at 12.5 years another increase begins. CONCLUSION These first WC and WHtR percentiles may be useful for clinical and epidemiological use in Switzerland until official, validated references become available. An advantage in using WHtR seems to be that it is not age dependent at certain levels and it may therefore be possible to use a single cut-off value for all children.