Associations of waist circumference to height ratio and body mass index through childhood and adolescence on blood pressure and risk of young adult hepatic steatosis: a cohort study

Objective
Body mass index (BMI), and its adjustment for age and sex as a z-score, is a common measure of excess weight but performs poorly in children. Waist circumference to height ratio (WHtR), which reflects excess adiposity, may be a useful alternative. We explored the associations between WHtR and BMI from childhood through adulthood and hepatic steatosis and systolic blood pressure (SBP).

Design
Participants (n=2193) from the Avon Longitudinal Study of Parents and Children were categorised into eight groups based on criteria for assessing excess adiposity at 7, 15 and 24 years using WHtR≥0.5, and excess weight using established age-specific BMI cut-off values. Regression models were fitted assessing associations between the groups and hepatic steatosis and SBP at age 24.

Results
Adult excess adiposity (WHtR) and excess weight (BMI) both associate with increased risk of hepatic steatosis: risk ratios (RR) 9.3 (95% CI 6.4 to 13.6) and 8.8 (95% CI 5.8 to 13.5), respectively, compared with always having healthy parameters. Excess adiposity in childhood and adulthood increases the associated risk (RR 11.4 (95% CI 6.2 to 20.9)), but not for excess weight, compared with adulthood alone (RR 7.6 (95% CI 3.9 to 15.1)). Both excess adiposity (RR 14.8 (95% CI 10.0 to 21.7)) and weight (RR 11.6 (95% CI 7.1 to 19.0)) in adolescence and adulthood associate with greater risk than adulthood alone. Positive associations with SBP were observed for excess adiposity or weight in adulthood only, childhood and adulthood, and adolescence and adulthood, and for persistent adiposity/weight, using both measures.

Implications
Excess adiposity or weight in early life, continuing to adulthood, elevates hepatic steatosis risk and associates with increased SBP in adulthood. These findings highlight the impact of youth adiposity and weight on later health outcomes. The strong association of WHtR and hepatic steatosis risk suggests it may be an alternative to BMI, with potential use in paediatric risk stratification.