Objective To examine whether neonatal non-hemolytic hyperbilirubinemia is associated with adult neuropsychiatric disability and cognitive function.

Methods The study included all men born as singletons ≥35 gestational weeks in two Danish counties from 1 January1977 to 31 December 1983 that registered at conscription in a Danish region. Their infant levels of hyperbilirubinemia was ascertained from hospital records. At conscription, the prevalence of neurologic conditions and performance on a standard group intelligence test (Boerge Prien test) was compared between men with and without neonatal non-hemolytic hyperbilirubinemia.

Results The study group consisted of 463 conscripts exposed to neonatal non-hemolytic hyperbilirubinemia and 12 718 unexposed conscripts. The median value of maximum serum bilirubin concentration was 256 µmol/l (range 105–482). Among the exposed, 5.6% were deemed unfit for military service due to a neurologic or a psychiatric condition, compared with 4.8% among the unexposed (prevalence ratio 1.18, 95% CI 0.81 to 1.73). Among men with Boerge Prien measurement, mean Boerge Prien test score among 391 exposed men was 42.4 points compared with 43.4 points among 11 248 unexposed men (mean difference 1.0 points, 95% CI 0.0 to 1.9). There was no association between level of hyperbilirubinemia and cognitive score. Adjusted prevalence ratio of obtaining a Boerge Prien test score in the lowest quartile was 1.04 (95% CI 0.87 to 1.23).

Conclusion The study found no evidence of an association between neonatal non-hemolytic hyperbilirubinemia and adult neurodevelopment and cognitive performance in male conscripts. Since cognitive performance was not associated with the severity of hyperbilirubinemia we ascribe the slightly lower cognitive scores among exposed to uncontrolled confounding.