When newborns with a too low birth weight are treated, even their non-affected siblings benefit. This is the conclusion of a recent IZA Discussion Paper authored by N. Meltem Daysal, Sanni Breining, Marianne Simonsen, and Mircea Trandafir, using data from Danish children born between 1982 and 1993.
During the past few decades, medical spending for the very young increased substantially faster than spending for the average individual. These early-life medical interventions substantially improve the short-term health and long-term academic achievement of treated children. But it doesn’t stop here: The authors investigate whether the beneficial effects of early-life medical treatments also spill over to the siblings of treated children.
One of the major challenges when investigating the effect of medical treatments is that individuals in worse health are more likely to be treated. Therefore, simple comparisons of children who receive medical treatments with those who do not are misleading. To address this issue, the authors exploit the fact that Danish medical guidelines use a 1,500-gram birth weight cutoff for specialized medical treatments. The idea: Although children who weigh slightly less than 1,500 grams and children who weigh slightly more than 1,500 grams have similar underlying health, the former are more likely to receive additional medical treatments.
Using the comparison of babies just below and above this 1,500-gram cutoff as a quasi-experiment, the study finds that siblings of children slightly below the cutoff have similar health outcomes relative to the siblings of children slightly above the cutoff. However, they have significantly better academic achievement in terms of higher 9th grade language and math test scores, as well as higher probability of enrolling in a high school by age 19.
Why are siblings affected?
Early-life medical treatments may affect the academic performance of siblings through direct exposure to the same treatments or via indirect channels arising from the better health and academic achievement of the treated children. The authors show that direct exposure to treatments or improved parental health education, e.g., through increased doctor visits, are unlikely to be the main explanation behind their results. They reach the same conclusion with respect to potential changes in total household resources, such as income or time available for child-care, changes in the allocation of resources across siblings, or the general family environment, e.g., family structure.
Instead, they interpret their findings as suggestive of the importance of parent-child and sibling interactions. First, consistent with previous medical findings, they show that treated children are less likely to have an intellectual disability. Second, they find that the mothers of treated children have better mental health soon after the child is born. Finally, they find larger effects on siblings with characteristics that are most closely tied to the quality of peer interactions; more specifically for girls, siblings of the same gender as the treated child, and younger siblings.
As medical expenditures keep increasing throughout the developed world, understanding the efficacy of early-life medical interventions becomes even more important. Overall, these results suggest that medical treatments for very low birth weight children may have effects on other family members that raise their net benefits.