Background: There is accumulating evidence that rapid infant growth is associated with subsequent metabolic risk, but less investigation of potential benefits. We tested the life history trade-off hypothesis that rapid infant growth is associated with lower risk of serious childhood morbidity (in particular, infection) proxied by hospital admission.
Methods: We studied term births (n = 7833, 94% follow-up) from a Chinese birth cohort, "Children of 1997," comprising 88% of births in Hong Kong in April and May 1997. We used multivariable negative binomial regression to examine the association of growth trajectory (5 categories) from birth to 12 months with subsequent hospital admissions until the child's 8th birthday. Potential confounders included sex, gestational age, parental education, type of birth hospital, infant feeding, and the presence of congenital disease.
Results: Infants with the slowest growth trajectory (smallest birth weight and slowest weight gain) were more likely to be hospitalized between 1 and 8 years of age-particularly for noninfectious illnesses. Infants in the 4 faster growth trajectories differed little in their risk of hospitalization. Adjusted incident rate ratios of hospitalization for infectious diseases were 0.93 (95% confidence interval = 0.81-1.06), 0.97 (0.85-1.12), 0.91 (0.78-1.06), and 0.92 (0.79-1.08) for the 4 faster growth trajectories compared with the slowest. Results were similar when growth was assessed as change in weight-for-age z-score.
Conclusion: Fast infant growth does not protect against serious infectious morbidity, but low birth weight infants born with slow growth are more vulnerable to serious morbidity, either as a consequence of poor growth or as a parallel marker of underlying health state. Whether maximum growth rates are ideal should be considered, as should the effects of infant over-nutrition.