Effects of sex on auditory brainstem responses in infancy and early childhood

Global, Regional, and National Burdens of Hearing Loss for Children and Adolescents from 1990 to 2019: A Trend Analysis

This study presents a comprehensive analysis of global, regional, and national trends in the burden of hearing loss (HL) among children and adolescents from 1990 to 2019, using data from the Global Burden of Disease study. Over this period, there was a general decline in HL prevalence and years lived with disability (YLDs) globally, with average annual percentage changes (AAPCs) of -0.03% (95% uncertainty interval [UI], -0.04% to -0.01%; p = 0.001) and -0.23% (95% UI, -0.25% to -0.20%; p < 0.001). Males exhibited higher rates of HL prevalence and YLDs than females. Mild and moderate HL were the most common categories across all age groups, but the highest proportion of YLDs was associated with profound HL [22.23% (95% UI, 8.63%-57.53%)]. Among females aged 15-19 years, the prevalence and YLD rates for moderate HL rose, with AAPCs of 0.14% (95% UI, 0.06%-0.22%; p = 0.001) and 0.13% (95% UI, 0.08%-0.18%; p < 0.001). This increase is primarily attributed to age-related and other HL (such as environmental, lifestyle factors, and occupational noise exposure) and otitis media, highlighting the need for targeted research and interventions for this demographic. Southeast Asia and Western Sub-Saharan Africa bore the heaviest HL burden, while High-income North America showed lower HL prevalence and YLD rates but a slight increasing trend in recent years, with AAPCs of 0.13% (95% UI, 0.1%-0.16%; p < 0.001) and 0.08% (95% UI, 0.04% to 0.12%; p < 0.001). Additionally, the analysis revealed a significant negative correlation between sociodemographic index (SDI) and both HL prevalence (r = -0.74; p < 0.001) and YLD (r = -0.76; p < 0.001) rates. However, the changes in HL trends were not significantly correlated with SDI, suggesting that factors beyond economic development, such as policies and cultural practices, also affect HL. Despite the overall optimistic trend, this study emphasizes the continued need to focus on specific high-risk groups and regions to further reduce the HL burden and enhance the quality of life for affected children and adolescents.

Effects of neurodevelopmental risk factors on brainstem maturation in premature infants

BACKGROUND

Interpeak latencies (IPL), as measured by the auditory brainstem-evoked responses (ABR) test, represent the conduction time, and therefore the maturation of the brainstem auditory pathway. We aimed to study the effect of various risk factors for the neurodevelopmental delay on the conduction time in the auditory pathway among normal hearing premature infants, at term postmenstrual age (PMA).

METHODS

Retrospective analysis of 239 premature infants (gestational age 32.5 ± 2.1 weeks, birth weight 1827 ± 483 g). Interpeak latencies, demographic data, and risk factors were recorded.

RESULTS

Sex, PMA at ABR test, being small for gestational age (SGA), intraventricular hemorrhage (IVH) or periventricular leukomalacia (PVL), and days of invasive ventilation were found to significantly affect the IPL's in the auditory pathway in a univariate analysis. Multivariable regression analysis revealed that male sex and less advanced PMA at the examination were independent factors associated with prolonged IPL's, while bronchopulmonary dysplasia, IVH or PVL and being SGA shortened the IPL's. Non-invasive mechanical ventilation, did not affect the caudal part of the auditory pathway, despite its high noise level.

CONCLUSIONS

Among various risk factors for the neurodevelopmental delay, male sex was associated with delayed, while IVH or PVL, BPD and SGA could be associated with accelerated auditory brainstem maturation.

IMPACT

Auditory brainstem-evoked response (ABR) test, among normal hearing infants, can serve as a clinical tool to assess brainstem auditory maturation. Different neurodevelopmental risk factors could have different effects on the maturity of the auditory pathway. Male sex is significantly associated with prolonged interpeak latencies (IPL) among preterm and term infants, while intraventricular hemorrhage or periventricular leukomalacia, bronchopulmonary dysplasia, and being small for gestation age may be associated with shortened IPL The corrected age at ABR testing is of significance, among preterm and term infants.

Electrophysiological markers of cochlear function correlate with hearing-in-noise performance among audiometrically normal subjects

Hearing loss caused by noise exposure, ototoxic drugs, or aging results from the loss of sensory cells, as reflected in audiometric threshold elevation. Animal studies show that loss of hair cells can be preceded by loss of auditory-nerve peripheral synapses, which likely degrades auditory processing. While this condition, known as cochlear synaptopathy, can be diagnosed in mice by a reduction of suprathreshold cochlear neural responses, its diagnosis in humans remains challenging. To look for evidence of cochlear nerve damage in normal hearing subjects, we measured their word recognition performance in difficult listening environments and compared it to cochlear function as assessed by otoacoustic emissions and click-evoked electrocochleography. Several electrocochleographic markers were correlated with word scores, whereas distortion product otoacoustic emissions were not. Specifically, the summating potential (SP) was larger and the cochlear nerve action potential (AP) was smaller in those with the worst word scores. Adding a forward masker or increasing stimulus rate reduced SP in the worst performers, suggesting that this potential includes postsynaptic components as well as hair cell receptor potentials. Results suggests that some of the variance in word scores among listeners with normal audiometric threshold arises from cochlear neural damage.NEW & NOTEWORTHY Recent animal studies suggest that millions of people may be at risk of permanent impairment from cochlear synaptopathy, the age-related and noise-induced degeneration of neural connections in the inner ear that "hides" behind a normal audiogram. This study examines electrophysiological responses to clicks in a large cohort of subjects with normal hearing sensitivity. The resultant correlations with word recognition performance are consistent with an important contribution cochlear neural damage to deficits in hearing in noise abilities.

Age-related hearing loss: Why we need to think about sex as a biological variable

It has long been known that age-related hearing loss (ARHL) is more common, more severe, and with an earlier onset in men compared to women. Even in the absence of confounding factors such as noise exposure, these sexdifferences in susceptibility to ARHL remain. In the last decade, insight into the pleiotrophic nature by which estrogen signaling can impact multiple signaling mechanisms to mediate downstream changes in gene expression and/or elicit rapid changes in cellular function has rapidly gathered pace, and a role for estrogen signaling in the biological pathways that confer neuroprotection is becoming undeniable. Here I review the evidence why we need to consider sex as a biological variable (SABV) when investigating the etiology of ARHL. Loss of auditory function with aging is frequency-specific and modulated by SABV. Evidence also suggests that differences in cochlear physiology between women and men are already present from birth. Understanding the molecular basis of these sex differences in ARHL will accelerate the development of precision medicine therapies for ARHL.

Estrogenic modulation of auditory processing: a vertebrate comparison

Sex-steroid hormones are well-known regulators of vocal motor behavior in several organisms. A large body of evidence now indicates that these same hormones modulate processing at multiple levels of the ascending auditory pathway. The goal of this review is to provide a comparative analysis of the role of estrogens in vertebrate auditory function. Four major conclusions can be drawn from the literature: First, estrogens may influence the development of the mammalian auditory system. Second, estrogenic signaling protects the mammalian auditory system from noise- and age-related damage. Third, estrogens optimize auditory processing during periods of reproductive readiness in multiple vertebrate lineages. Finally, brain-derived estrogens can act locally to enhance auditory response properties in at least one avian species. This comparative examination may lead to a better appreciation of the role of estrogens in the processing of natural vocalizations and mayprovide useful insights toward alleviating auditory dysfunctions emanating from hormonal imbalances.

Gender effects in auditory brainstem responses to air- and bone-conducted clicks in neonates

Examinations of gender differences in auditory brainstem response (ABR) wave V latencies and thresholds to air- and bone-conducted clicks were undertaken with neonates. Two hundred and two full-term neonates participated (i.e., 103 males and 99 females). Wave V latency measures for air- and bone-conducted click stimuli of 30, 45, and 60 dB nHL and 15 and 30 dB nHL, respectively, and thresholds to air- and bone-conducted clicks were determined. Female newborns displayed statistically significant shorter wave V latencies than male newborns for air-conducted click stimuli (i.e., approximately 0.2-0.3 ms; P=.0016). There were no significant gender differences in wave V latencies to bone-conducted click stimuli (P=.11). With respect to ABR thresholds, no statistically significant differences were observed for either air-conducted clicks (P=.054) or bone-conducted clicks (P=.18).

EDUCATIONAL OBJECTIVES

As a result of this activity, the participant will be able to (1) describe gender differences in ABR wave V latencies and thresholds to air- and bone-conducted clicks with neonates and (2) summarize possible explanations for observed gender differences in ABR wave V latencies and thresholds to air- and bone-conducted clicks with neonates.

Brain-stem auditory evoked potentials (BAEPs): maturation of interpeak latency I-V (IPL I-V) in the first years of life

BAEPs were recorded from 89 healthy children aged 0.1-52.1 months. The maturation kinetics of interpeak latency I-V can be well approximated by an exponential model with a horizontal asymptote. Adult values are reached by about 3 years of life. Differences between males and females become significant when maturation is completed. A non-fragmented reference range for interpeak latency I-V in the first years of life is provided.

ABR latency in infants: properties and applications of various measures

ABR latency ratios have been proposed as useful clinical tools in the assessment of infants at risk for auditory or neurologic deficits. These parameters, together with classical absolute and interwave latency measures, were examined in 131 infants with normal ABR thresholds at 48-64 weeks post-conceptional age, and with no conventional risk factor for hearing impairment or neurological abnormality. Latency of wave I is unaffected by age or gender, but that of waves III and V decreases linearly with age and is smaller in females. These effects must be accounted for in clinical evaluation. However, latency ratios V/I, V/III and III/I show no significant age or gender effects. Wave I latency and the V/I latency ratio both permitted very good discrimination between normal infants and those with presumed conductive hearing losses, but the effects of sensorineural impairment have yet to be determined. On a priori grounds it seems improbable that latency ratios will outperform classical ABR parameters, at least for the goals and age range considered in this study.

Brain-stem auditory evoked response: normative values in children

Normative values of brain-stem auditory evoked response (BAER) derived from a large (N = 174) normal school age sample are presented. In our 4-14 years of age sample we found a significant influence of sex on some BAER components, and a significant influence of age on others. The norms have been computed according to these influences. Particular aspects of the influence of age and sex are also discussed.