Birth order and pediatric traumatic brain injury
Date
2022
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Abstract
Pediatric traumatic brain injury (TBI) is a signifcant problem of public health importance worldwide.
Large population-based studies on the efect of birth order on health phenomena are exceedingly
rare. This study examines the relationship between birth order and risk for pediatric TBI among sibling
groups. We performed a retrospective cohort study following 59,469 Finnish newborns from 1987 until
age 18 years. Data on frst diagnosis of TBI was recorded within the 1987 Finnish Birth Cohort (FBC).
Compared with frst born siblings, later born siblings had an increased risk of TBI during the follow-up
period (hazard ratio [HR] 1.02; 95% confdence interval [CI] 0.91–1.14 for second born, HR 1.09; 95%
CI 0.95 1.26 for third born, HR 1.28; 95% CI 1.08–1.53 for fourth or higher). When adjusted for sex and
maternal age at child’s birth, HRs (95% CIs) for TBI during the follow-up period were 1.12 (0.99–1.26)
for second born, 1.31 (1.12–1.53) for third born and 1.61 (1.33–1.95) for fourth born or higher children,
respectively. Within this large register-based population-wide study, order of birth modifed risk for
pediatric TBI among sibling groups. Taken together, these study fndings may serve to stimulate
further inquiry into genetic, psychological, or psychosocial factors which underlie diferences in risk
and depth of efect within and between sibling groups.