52 Underweight in the first 2 years of life and growth in later childhood

Abstract

Abstract Background Underweight occurs when caloric intake is insufficient to maintain growth. While it has long been assumed that underweight in the first 2 years of life is associated with lower growth potential in later childhood, longer term growth outcomes in high income countries are unclear. Objectives The primary objective was to evaluate the relationship between underweight in the first 2 years of life and body mass index z-score (zBMI) in later childhood. Secondly, we examined the relationship between underweight in the first 2 years of life and weight-for-age z-score (WAZ) and height-for-age z-score (HAZ) in later childhood, and how sex and the zBMI growth trajectory in the first 2 years of life modify these associations. Design/Methods This was a prospective cohort study conducted through The Applied Research Group for Kids (TARGetKids!) practice-based research network. Healthy children 0-10 years of age were included. The primary exposure was underweight in the first 2 years of life using zBMI <-2 as per the World Health Organization (WHO). The primary outcome was zBMI, and secondary outcomes were WAZ and HAZ between 2 and 10 years of age. Linear mixed effects models were used for the primary and secondary analysis to take into account multiple growth measures over time. Interaction terms for sex, and the zBMI growth trajectory in the first 2 years of life were used to explore effect modification. Results Among the 5,803 children included in the primary analysis, the mean age was 4.07 months, and 52.2% were male at baseline. In adjusted models, underweight in the first 2 years of life was associated with lower zBMI, lower WAZ, and higher odds of underweight at 2, 5, and 10 years of age (p <0.0001). Underweight in the first 2 years was associated with a lower HAZ at 2 years of age (p<0.0001), but not 5 (p=0.08), or 10 years of age (p=0.8). Females with underweight had lower zBMI and WAZ at 5 and 10 years of age, and lower HAZ at 10 years of age compared to males with underweight (p<0.05). Children with underweight and lower growth trajectory in the first 2 years had lower zBMI, WAZ, HAZ, and higher odds of underweight at 2, 5, and 10 years of age compared to children who did not have underweight (p<0.05). Children with underweight and high growth trajectory in the first 2 years had similar zBMI, WAZ, higher HAZ and lower odds of overweight at 10 years of age (p<0.05), compared to children who did not have underweight. Conclusion Underweight in the first 2 years of life was associated with lower growth in later childhood. These relationships were amplified for females and children with underweight who had low growth trajectory in the first 2 years of life and were attenuated among children with underweight who had high growth trajectory in the first 2 years of life.