Body Mass Index Z-score vs Weight-for-Length Z-score in Infancy and Cardiometabolic Outcomes at Age 8-10 Years.

Objectives To confirm that WHO weight-for-length Z-scores (zWFL) and WHO body mass index Z-scores (zBMI) in infancy are associated with adiposity and cardiometabolic measures at 8-10 years old and to compare the predictive ability of the two methods. Study design WFL and BMI Z-scores at 6, 12, and 18 months of age were computed using data extracted from health booklets, among participants in the Quebec Adipose and Lifestyle InvesTigation in Youth prospective cohort (n = 464). Outcome measures at 8-10 years included adiposity, lipid profile, blood pressure, and insulin dynamics. The relationships between zWFL, zBMI and each outcome were estimated using multivariable linear regression models. Outcome prediction at 8-10 years was compared between the two methods using eta-squared and the Lin concordance correlation. Results zWFL and zBMI were associated with all measures of adiposity at 8-10 years. Associations with other cardiometabolic measures were less consistent. For both zWFL and zBMI across infancy, eta-squared were highly similar and the Lin coefficients were markedly high ( > 0.991) for all outcomes. Conclusion There was no evidence that zBMI and zWFL in infancy differed in their ability to predict adiposity and cardiometabolic measures in childhood. This lends support to the sole use of zBMI for growth monitoring and screening of overweight and obesity from birth to 18 years.