Objective: To examine the influence of age and gender on the waist:height ratio (WHTR) in children and to compare changes over time in WHTR, a measure of central fatness in British children.
Design: Representative cross-sectional surveys in 1977, 1987 and 1997.
Setting: Great Britain and Northern Ireland.
Participants: Survey 1: children aged 5-16 years measured in 1977 (boys) and 1987 (girls) (BSI, n=8135) and Survey 2: children aged 11-16 measured in 1997 (NDNS, n=773).
Outcome measures: From Survey 1, waist: height ratio related to age and sex and the proportion of children with a WHTR greater than 0.500 (a boundary value suggested for adults). From Survey 2, comparison of WHTR in children with that from Survey 1 and the actual proportion of children with a WHTR greater than 0.500 compared with the expected proportion using the survey 1 as reference.
Results: WHTR decreased with age (P<0.01 for trend), with the mean WHTR being significantly lower in girls (P<0.01). WHTR was significantly greater in children in Survey 2 compared with those measured 10 and 20 years earlier in Survey 1 (P<0.0001). The proportion of children where WHTR exceeded the 0.500 boundary value in Survey 2 was 17% of boys and 11.7% of girls (against 5.0 and 1.5%, respectively, in Survey 1, P<0.0001). The increase in WHTR in boys exceeded that in girls.
Conclusions: Values of WHTR during the past 10-20 years have increased greatly showing that central fatness in children has risen dramatically. WHTR is more closely linked to childhood morbidity than body mass index (BMI) and we suggest it should be used as an additional or alternative measure to BMI in children as well as adults. A simple public health message that is the same for adults and children of both sexes and all ages could be stated as 'keep your waist circumference to less than half your height'.