Permanent childhood hearing impairment in infants admitted to the neonatal intensive care unit: nested case-control study

Noise or sound management in the neonatal intensive care unit for preterm or very low birth weight infants

BACKGROUND

Infants in the neonatal intensive care unit (NICU) are subjected to different types of stress, including sounds of high intensity. The sound levels in NICUs often exceed the maximum acceptable level recommended by the American Academy of Pediatrics, which is 45 decibels (dB). Hearing impairment is diagnosed in 2% to 10% of preterm infants compared to only 0.1% of the general paediatric population. Bringing sound levels under 45 dB can be achieved by lowering the sound levels in an entire unit; by treating the infant in a section of a NICU, in a 'private' room, or in incubators in which the sound levels are controlled; or by reducing sound levels at the individual level using earmuffs or earplugs. By lowering sound levels, the resulting stress can be diminished, thereby promoting growth and reducing adverse neonatal outcomes. This review is an update of one originally published in 2015 and first updated in 2020.

OBJECTIVES

To determine the benefits and harms of sound reduction on the growth and long-term neurodevelopmental outcomes of neonates.

SEARCH METHODS

We used standard, extensive Cochrane search methods. On 21 and 22 August 2023, a Cochrane Information Specialist searched CENTRAL, PubMed, Embase, two other databases, two trials registers, and grey literature via Google Scholar and conference abstracts from Pediatric Academic Societies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) or quasi-RCTs in preterm infants (less than 32 weeks' postmenstrual age (PMA) or less than 1500 g birth weight) cared for in the resuscitation area, during transport, or once admitted to a NICU or stepdown unit. We specified three types of intervention: 1) intervention at the unit level (i.e. the entire neonatal department), 2) at the section or room level, or 3) at the individual level (e.g. hearing protection).

DATA COLLECTION AND ANALYSIS

We used the standardised review methods of Cochrane Neonatal to assess the risk of bias in the studies. We used the risk ratio (RR) and risk difference (RD), with their 95% confidence intervals (CIs), for dichotomous data. We used the mean difference (MD) for continuous data. Our primary outcome was major neurodevelopmental disability. We used GRADE to assess the certainty of the evidence.

MAIN RESULTS

We included one RCT, which enroled 34 newborn infants randomised to the use of silicone earplugs versus no earplugs for hearing protection. It was a single-centre study conducted at the University of Texas Medical School in Houston, Texas, USA. Earplugs were positioned at the time of randomisation and worn continuously until the infants were 35 weeks' postmenstrual age (PMA) or discharged (whichever came first). Newborns in the control group received standard care. The evidence is very uncertain about the effects of silicone earplugs on the following outcomes. • Cerebral palsy (RR 3.00, 95% CI 0.15 to 61.74)and Mental Developmental Index (MDI) (Bayley II) at 18 to 22 months' corrected age (MD 14.00, 95% CI 3.13 to 24.87); no other indicators of major neurodevelopmental disability were reported. • Normal auditory functioning at discharge (RR 1.65, 95% CI 0.93 to 2.94) • All-cause mortality during hospital stay (RR 2.07, 95% CI 0.64 to 6.70; RD 0.20, 95% CI -0.09 to 0.50) • Weight (kg) at 18 to 22 months' corrected age (MD 0.31, 95% CI -1.53 to 2.16) • Height (cm) at 18 to 22 months' corrected age (MD 2.70, 95% CI -3.13 to 8.53) • Days of assisted ventilation (MD -1.44, 95% CI -23.29 to 20.41) • Days of initial hospitalisation (MD 1.36, 95% CI -31.03 to 33.75) For all outcomes, we judged the certainty of evidence as very low. We identified one ongoing RCT that will compare the effects of reduced noise levels and cycled light on visual and neural development in preterm infants.

AUTHORS' CONCLUSIONS

No studies evaluated interventions to reduce sound levels below 45 dB across the whole neonatal unit or in a room within it. We found only one study that evaluated the benefits of sound reduction in the neonatal intensive care unit for hearing protection in preterm infants. The study compared the use of silicone earplugs versus no earplugs in newborns of very low birth weight (less than 1500 g). Considering the very small sample size, imprecise results, and high risk of attrition bias, the evidence based on this research is very uncertain and no conclusions can be drawn. As there is a lack of evidence to inform healthcare or policy decisions, large, well designed, well conducted, and fully reported RCTs that analyse different aspects of noise reduction in NICUs are needed. They should report both short- and long-term outcomes.

Comprehensive Gene Panel Testing for Hearing Loss in Children: Understanding Factors Influencing Diagnostic Yield

OBJECTIVE

To evaluate factors influencing the diagnostic yield of comprehensive gene panel testing (CGPT) for hearing loss (HL) in children and to understand the characteristics of undiagnosed probands.

STUDY DESIGN

This was a retrospective cohort study of 474 probands with childhood-onset HL who underwent CGPT between 2016 and 2020 at a single center. Main outcomes and measures included the association between clinical variables and diagnostic yield and the genetic and clinical characteristics of undiagnosed probands.

RESULTS

The overall diagnostic yield was 44% (209/474) with causative variants involving 41 genes. While the diagnostic yield was high in the probands with congenital, bilateral, and severe HL, it was low in those with unilateral, noncongenital, or mild HL; cochlear nerve deficiency; preterm birth; neonatal intensive care unit admittance; certain ancestry; and developmental delay. Follow-up studies on 49 probands with initially inconclusive CGPT results changed the diagnostic status to likely positive or negative outcomes in 39 of them (80%). Reflex to exome sequencing on 128 undiagnosed probands by CGPT revealed diagnostic findings in 8 individuals, 5 of whom had developmental delays. The remaining 255 probands were undiagnosed, with 173 (173/255) having only a single variant in the gene(s) associated with autosomal recessive HL and 28% (48/173) having a matched phenotype.

CONCLUSION

CGPT efficiently identifies the genetic etiologies of HL in children. CGPT-undiagnosed probands may benefit from follow-up studies or expanded testing.

An Animal Model of Neonatal Intensive Care Unit Exposure to Light and Sound in the Preterm Infant

According to the World Health Organization, ∼15 million children are born prematurely each year. Many of these infants end up spending days to weeks in a neonatal intensive care unit (NICU). Infants who are born prematurely are often exposed to noise and light levels that affect their auditory and visual development. Children often have long-term impairments in cognition, visuospatial processing, hearing, and language. We have developed a rodent model of NICU exposure to light and sound using the Mongolian gerbil (Meriones unguiculatus), which has a low-frequency human-like audiogram and is altricial. To simulate preterm infancy, the eyes and ears were opened prematurely, and animals were exposed to the NICU-like sensory environment throughout the gerbil's cortical critical period of auditory development. After the animals matured into adults, auditory perceptual testing was carried out followed by auditory brainstem response recordings and then histology to assess the white matter morphology of various brain regions. Compared to normal hearing control animals, NICU sensory-exposed animals had significant impairments in learning at later stages of training, increased auditory thresholds reflecting hearing loss, and smaller cerebellar white matter volumes. These have all been reported in longitudinal studies of preterm infants. These preliminary results suggest that this animal model could provide researchers with an ethical way to explore the effects of the sensory environment in the NICU on the preterm infant's brain development.

Newborn Hearing Screening with Two-Step Protocol and Risk Factor Identification: Our Experience at a Tertiary Care Centre in Eastern India

Objective

To estimate the prevalence of hearing loss and identify the high-risk factors among neonates with hearing loss.

Methods

Retrospective study done on 1054 infants in a tertiary care centre in Eastern India from 2020 to 2021 and approved by the Institutional Ethics Committee. A two-step protocol is used for screening. In the well-nursed group, OAE and BOA were performed. In the case of REFER results for automated ABR following OAE evaluation in well-nursed babies, a detailed audiological evaluation was scheduled to be carried out using diagnostic ABR within one month of age. In the high-risk group, hearing screening includes OAE, BOA, and AABR evaluations. AABR evaluation was performed as a part of the screening protocol irrespective of the results of OAE screening as PASS or REFER.

Results

In our study among 1053 neonates screened, 375 were in the risk category, and 679 were without risk factors. The overall prevalence of hearing loss in neonates was 22.78 per 1000 screened neonates and 56 per 1000 among high-risk neonates. In the high-risk group, we were able to identify 4 cases of Auditory spectrum neuropathy disorder with the use of AABR during 1st step of screening. In multivariate regression analysis, the risk factors for hearing loss identified were NICU stay (OR = 3.6, 95% CI = 1.1-12.03) and Craniofacial anomalies (OR = 55.37, 95% CI = 16.48- 186.01).

Conclusion

Early neonatal screening helps in the detection, intervention, and rehabilitation of hearing loss. The use of AABR in risk infant screening enhanced the chance of detection of auditory spectrum neuropathy disorder (ASND) cases.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-023-03723-3.

Maternal, Perinatal, and Postnatal Predisposing Factors of Hearing Loss in Full-Term Children: A Matched Case-Control Study

INTRODUCTION

Studies on risk factors for childhood hearing loss (HL) are usually based on questionnaires or small sample sizes. We conducted a nationwide population-based case-control study to comprehensively analyze the maternal, perinatal, and postnatal risk factors for HL in full-term children.

METHODS

We retrieved data from three nationwide databases related to maternal characteristics, perinatal comorbidities, and postnatal characteristics and adverse events. We used 1:5 propensity score matching to include 12,873 full-term children with HL and 64,365 age-, sex-, and enrolled year-matched controls. Conditional logistic regression was used to evaluate the risk factors for HL.

RESULTS

Among the various maternal factors, maternal HL (adjusted odds ratio [aOR]: 8.09, 95% confidence interval [95% CI]: 7.16-9.16) and type 1 diabetes (aOR: 3.79, 95% CI: 1.98-7.24) had the highest odds of childhood hearing impairment. The major perinatal risk factors for childhood hearing impairment included ear malformations (aOR: 58.78, 95% CI: 37.5-92.0) and chromosomal anomalies (aOR: 6.70, 95% CI: 5.25-8.55), and the major postnatal risk factors included meningitis (aOR: 2.08, 95% CI: 1.18-3.67) and seizure (aOR: 3.71, 95% CI: 2.88-4.77). Other factors included acute otitis media, postnatal ototoxic drug use, and congenital infections.

CONCLUSIONS

Many risk factors for childhood HL identified in our study are preventable, such as congenital infection, meningitis, ototoxic drug use, and some maternal comorbidities. Accordingly, more effort is required to prevent and control the severity of maternal comorbidities during pregnancy, initiate genetic diagnostic evaluation for high-risk children, and aggressive screening for neonatal infections.

Risk patterns associated with transient hearing impairment and permanent hearing loss in infants born very preterm: A retrospective study

AIM

To determine the risk patterns associated with transient hearing impairment (THI) and permanent hearing loss (PHL) of infants born very preterm who failed hearing screenings.

METHOD

We enrolled 646 infants (347 males, 299 females) born at no more than 30 weeks' gestation between 2006 and 2020 who received auditory brainstem response screening at term-equivalent age. Audiological examinations of infants who failed the screening revealed THI, when hearing normalized, or PHL, defined as a persistent unilateral or bilateral hearing threshold above 20 dB. Principal component analysis (PCA) was used to characterize risk patterns.

RESULTS

Among the 646 infants, 584 (90.4%) had normal hearing, 42 (6.5%) had THI, and 20 (3.1%) had PHL. Compared with the group with normal hearing, the THI and PHL groups had significantly higher rates of neurodevelopmental impairment at 24 months corrected age. PCA of risk patterns showed the THI group and especially the PHL group had more severe haemodynamic and respiratory instability. Moreover, severe intraventricular haemorrhage (IVH) was also a risk for PHL. Propensity score matching revealed an association of haemodynamic and respiratory instability with PHL.

INTERPRETATION

In infants born preterm, the severity and duration of haemodynamic and respiratory instability are risk patterns for both THI and PHL; severe IVH is an additional risk for PHL.

WHAT THIS PAPER ADDS

Neurodevelopmental delay was more common in infants born preterm who failed hearing screening. Principal component analysis revealed the risk patterns associated with hearing impairment. Haemodynamic-respiratory instability was associated with transient and permanent hearing impairment outcomes. Severe haemodynamic-respiratory instability and intraventricular haemorrhage was associated with permanent hearing loss.

Preterm Brain Injury and Neurodevelopmental Outcomes: A Meta-analysis

CONTEXT

Preterm brain injuries are common; neurodevelopmental outcomes following contemporary neonatal care are continually evolving.

OBJECTIVE

To systematically review and meta-analyze neurodevelopmental outcomes among preterm infants after intraventricular hemorrhage (IVH) and white matter injury (WMI).

DATA SOURCES

Published and grey literature were searched across 10 databases between 2000 and 2021.

STUDY SELECTION

Observational studies reporting 3-year neurodevelopmental outcomes for preterm infants with IVH or WMI compared with preterm infants without injury.

DATA EXTRACTION

Study characteristics, population characteristics, and outcome data were extracted.

RESULTS

Thirty eight studies were included. There was an increased adjusted risk of moderate-severe neurodevelopmental impairment after IVH grade 1 to 2 (adjusted odds ratio 1.35 [95% confidence interval 1.05-1.75]) and IVH grade 3 to 4 (adjusted odds ratio 4.26 [3.25-5.59]). Children with IVH grade 1 to 2 had higher risks of cerebral palsy (odds ratio [OR] 1.76 [1.39-2.24]), cognitive (OR 1.79 [1.09-2.95]), hearing (OR 1.83 [1.03-3.24]), and visual impairment (OR 1.77 [1.08-2.9]). Children with IVH grade 3 to 4 had markedly higher risks of cerebral palsy (OR 4.98 [4.13-6.00]), motor (OR 2.7 [1.52-4.8]), cognitive (OR 2.3 [1.67-3.15]), hearing (OR 2.44 [1.42-4.2]), and visual impairment (OR 5.42 [2.77-10.58]). Children with WMI had much higher risks of cerebral palsy (OR 14.91 [7.3-30.46]), motor (OR 5.3 [3-9.36]), and cognitive impairment (OR 3.48 [2.18-5.53]).

LIMITATIONS

Heterogeneity of outcome data.

CONCLUSIONS

Mild IVH, severe IVH, and WMI are associated with adverse neurodevelopmental outcomes. Utilization of core outcome sets and availability of open-access study data would improve our understanding of the nuances of these outcomes.

Hearing outcomes in preterm infants with confirmed hearing loss

OBJECTIVES

Premature infants are at high risk for hearing loss (HL). The aim of the present study is to assess the frequency of preterm infants affected by HL who experience hearing improvement over months and evaluate possible factors associated with hearing changes.

METHODS

This retrospective study was conducted in a third-level referral audiologic center. Preterm infants with a confirmed diagnosis of sensorineural HL within the first 3 months of life were reassessed at 18 months corrected age using the click-evoked auditory brainstem response between January 1, 2012, and June 30, 2020. The frequency of hearing improvement and associations between possible risk factors and hearing changes were evaluated.

RESULTS

A total of 138 preterm infants (71 male and 67 female; mean gestational age: 30⁺² weeks) were assessed. The percentages of hearing improvement and hearing threshold normalization were 58.7% (81/138) and 35.5% (49/138), respectively. We observed a higher frequency of hearing improvement among preterm infants who had received exclusive breastfeeding or mixed feeding compared with those who had received exclusive infant formula (80% versus 29.3%, P < 0.001).

CONCLUSION

This study confirms the importance of performing a long audiological follow-up and postponing the indication for cochlear implantation in children with a history of preterm birth. Because of the expression of mesenchymal stem cells and high total antioxidant capacity, breast milk might play a protective role in the auditory system of preterm infants. These findings could have important implications for clinical practice, positively impacting the long-term hearing outcomes of preterm infants.