Long-term Effects of Indirect Hyperbilirubinemia on Auditory and Neurological Functions in Term Newborns

Prospective Evaluation of Hearing Status in Neonatal Hyperbilirubinemia

Elevated bilirubin levels in neonates are commonly seen both physiologically and in pathological conditions. There are few articles describing the effects of elevated bilirubin levels on the auditory system. The objectives of this paper was to study the prevalence of hearing impairment in neonates with hyperbilirubinemia and assess outcome/reversibility of hearing impairment in these neonates with follow-up hearing evaluation. This was a prospective single centre, case control study. Cases: neonates, total bilirubin levels >15 mg/dl. Controls: <15 mg/dl. Exclusion criteria included neonates with neonatal hypoxia, intrauterine infections, sepsis or meningitis, infants with a family history of hearing loss, low birth weight, ototoxic medications, external and middle ear pathology. Otoacoustic emission testing (OAE) was done at birth. Neonates who fail OAE were advised follow up with Brainstem Evoked Response Audiometry (BERA) after 2 months. Neonates having abnormal BERA waves were called for follow up at 6 months. Out of 57 cases, 3 had failed OAE and had normal BERA waves on follow up at 2 months. Out of 60 controls, 5 had failed OAE and follow up BERA for 3 patients were normal and 2 babies were lost to follow up. No statistical significance in hearing impairment in hyperbilirubinemia v/s normal babies was noted. Elevated bilirubin levels in the absence of any other risk factors may not show significant changes in the hearing screening. Some effect owing to the p value close to being significant in cases has been noted. The same may not contribute to permanent hearing impairment as first OAE changes may be transient and seem to revert with age.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-023-04181-7.

Neonatal hyperbilirubinemia and repercussions on neurodevelopment: A systematic review

BACKGROUND

Accumulation of bilirubin above normal levels is considered a neurological risk factor for both premature and full-term newborns. This systematic review aimed to determine the effect of neonatal hyperbilirubinemia on neurodevelopment in preterm and full-term newborns.

METHODS

PubMed, EMBASE, Cochrane Library, CINAHL, PsycINFO, Scopus and Lilacs databases were searched for articles published until 1 June 2022. The quality of cohort and case-control studies was assessed with the Newcastle-Ottawa Scale, and the MINCir scale was used to evaluate the methodological quality of therapy studies or the therapeutic procedures. Premature neonates without neurological conditions and those born at term with hyperbilirubinemia as the sole risk factor were included. Studies reporting one or more neurodevelopmental outcomes were included with an inter-group comparison of a hyperbilirubinemia group versus a non-hyperbilirubinemia or non-pathological hyperbilirubinemia group. The main outcomes were auditory function, visual function, cognitive function, motor function, behavior, global development and neurological risk.

RESULTS

The search identified 951 studies, 19 of which (n = 2210 newborns) were finally included. Fifteen of the cohort and case-control studies presented low risk of bias, and six studies showed high methodological quality. Within the preterm population, hyperbilirubinemia as the sole risk factor was not shown to affect neurodevelopment. Auditory, neurological and motor development alterations were found in the population of full-term newborns with hyperbilirubinemia, which were more evident during the first year of life.

CONCLUSIONS

Elevated bilirubin levels may be a trigger for the onset of neurodevelopmental disorders in full-term infants during the first year of life. More studies are warranted in the preterm population with hyperbilirubinemia to draw conclusions about its impact on their neurodevelopment.