Risk Indicators for Hearing Impairment in Neonates

Abstract

To identify relation between prevalence of hearing impairment and risk factors at the time of birth in high risk neonates. A year-long study is performed at HBT Medical College and Dr. R. N. Cooper Municipal General Hospital, Vile Parle (west), Mumbai. The Study comprised of 478 high risk babies born between March 2016 and February 2017 and admitted in NICU of the hospital. Out of these 68 babies were either transferred to higher centre or took discharge against medical advice. A total of 410 babies completed the study. Additional 21 eligible babies died in NICU during the study. A Prospective Observational Study is used to analyse the findings of the study. Skew analysis of spread of prevalence across risk factors is used to establish higher prevalence of hearing impairment in high risk neonates. Cramer’s Moment Coefficient of Skewness and Corresponding Test Statistics are used for studying the skewness. Out of 410 babies screened during the study 5 babies were diagnosed with profound SNHL. The risk factors associated with babies is plotted against frequency of babies with Profound SNHL. The plot is found to be un-uniformly distributed and shows inclination towards higher prevalence with high risk babies. Sample skewness (G₁) value − 0.81 indicates moderately negative skewed sample. This means the number of babies with profound SNHL found by 3 stage screening is moderately concentrated at high risk weightage.

Introduction

Detecting hearing impairment at an early stage by behavioural responses from the child is a very difficult task. If a child is not screened at the time of birth then by the time hearing loss is suspected, audio-logically evaluated and appropriately managed two or more of these critical years are missed and the child loses an enormous developmental advantage. Substantial and irreversible deficits in speech, linguistic, and cognitive development leads to severe problems in communication at later stage which in turn has significant adverse effect on the learning ability, and academic and social performance of children [1, 2].

In developing countries like India, where disabled friendly social facilities are not widely available, children with hearing loss rarely receive any schooling and those who go for primary school dropout eventually. Adults with hearing impairment also have a much higher unemployment rate [1–3].

It’s the responsibility of medical system to develop culturally and financially acceptable ways of implementing infant hearing screening programs. Current paper focuses on identification of risk factors which indicates higher probability of Neonatal Hearing Impairment. Risk weightage assigned with risk factors of a child can indicate probability of neonatal hearing impairment. Accordingly children with higher risk can be selectively referred for hearing screening to ascertain the hearing condition.

Selective hearing screening based on risk factor identification is not an alternative to universal screening of neonates. But, this can work as cost effective measure to reduce the financial and infrastructural burden to screen all the children in low economic strata in a cost effective manner in developing countries like India.

Need of Study: Importance of Early Detection

The prevalence of congenital hearing loss has been reported to be 1–6 per thousand live births by American Speech Language Hearing Association. But several studies have shown higher prevalence in high risk neonates [4, 5]. Globally in children under 15 years of age, 60% of hearing loss is attributable to preventable causes. This figure is higher in low- and middle-income countries (75%) as compared to high-income countries (49%). Below is the list of preventable causes and corresponding instances of hearing loss globally [1, 2]:

• Infections such as mumps, measles, rubella, meningitis, cytomegalovirus infections, and chronic otitis media—Leads to 31% cases of preventable causes [1, 2].

• Complications at the time of birth, such as birth asphyxia, low birth weight, prematurity, and jaundice—Leads to 17% cases of preventable causes [1, 2].

• Use of ototoxic medicines in expecting mothers and babies—Leads to 4% cases of preventable causes [1, 2].

• Others—Leads to 8% cases of preventable causes [1, 2].

Inclusion Criteria

Babies admitted to NICU with at least one of the following risk factors [6]:

Birth asphyxia	Low/Large birth weight
Condition of labour and delivery (Leaking PV, MSL, LSCS, Birth Trauma)	Congenital anomaly
Consanguineous marriage	Family history of congenital deafness
Fetal factors (IUGR, Twins, Oligohydramnios)	Maternal factors (TORCH, PIH, GDM, RH-, Hypothyroid)
Meconium aspiration syndrome	Neonatal jaundice
Prematurity(< 37 weeks)	Refuse feed
Respiratory distress	Respiratory distress syndrome
Sepsis

Exclusion Criteria

• Neonate who were on ventilator support from birth to death.

• Active ear infections.

A two stage OAE screening followed by confirmatory BERA test was performed to find children with profound SNHL shown in Fig. 1

Fig. 1.

3 stage screening test

Figure 2 shows BERA test being performed in the final stage of screening on a baby for the study in Dr. R. N. Cooper Hospital and HBT Medical College.

Fig. 2.

BERA test on a baby during the study

Table 1 lists details of risk factors of babies found with profound SNHL by the three stage screening process.

Table 1.

Risk factors of babies identified with profound SNHL

S. no.	NICU stay days	Risk factors
1	38	MSL
2	9	LBW, Birth asphyxia, LSCS, Family history of congenital deafness
3	27	VLBW, Respiratory distress, Prematurity (< 37 weeks), Meconium aspiration syndrome, LSCS
4	21	LBW, Respiratory distress syndrome, Refuse feed, IUGR
5	130	VLBW, Birth asphyxia, Neonatal jaundice

It can be observed from the table that 4 out of 5 babies who were diagnosed with Profound SNHL have NICU stay of over 20 days and except 1st case all have 3 or more risk factors associated to them.

There is strong bias among children with longer NICU stay and more risk factors for hearing impairment. To further establish the relation between risk factors and hearing impairment following risk weightage were assigned to each baby:

• 1 for each risk factor

• 1 for birth weight out of normal range (< 2500 g or > 4000 g)

• 1 for NICU stay up to 20 days, and

• 2 for NICU stay more than 20 days.

Table 2 shows a summary of 3 stage screening test by listing risk weightage and corresponding count of instances of profound SNHL.

Table 2.

Prevalence of babies with profound SNHL across risk weightage

Risk weightage	Count of babies screened	Count of babies with profound SNHL
1	5	0
2	89	0
3	113	1
4	79	0
5	51	2
6	35	1
7	38	1
Sum	410	5

Figure 3 shows prevalence of profound SNHL corresponding to the risk weightage found in the study. It is apparent looking at the chart that the babies are not uniformly distributed across the risk weightage.

Fig. 3.

Prevalence of babies with profound SNHL across risk weightage

Its apparent from the chart that the number of babies found with Profound SNHL with high risk weightage is high compared to number of babies with low risk weightage.

Statistical Analysis

Skew analysis of spread of prevalence across risk factors is used to establish higher prevalence of hearing impairment in high risk neonates. Cramer’s Moment Coefficient of Skewness and Corresponding Test Statistics is used for studying the skewness [7].

• Skew Test Statistics of Babies Referred by 3 Stage Screening:

  • Sample skewness (G1): − 0.81.
  • 95% confidence interval of G1: − 2.13 to 0.51.

Sample skewness (G₁) value − 0.81 indicates moderately negatively skewed sample [7]. This means the number of babies with profound SNHL found by 3 stage screening is moderately concentrated at high risk weightage.

Discussion and Conclusion

According to study published by WHO in 2012 on the magnitude of disabling hearing loss based on 42 population-based studies there are 360 million persons in the world with disabling hearing loss (representing 5.3% of the world’s population). 91% of these are adults while 9% are children. The prevalence of disabling hearing loss in children is greatest in South Asia, Asia Pacific and Sub-Saharan Africa. Disabling hearing loss prevalence is unequal across the world and is more prominent in low income groups.

The time period from birth to 5 years of age is crucial for the development of speech and language. Hearing loss at an early age leads to difficulty in learning spoken language and affects overall emotional, cognitive and social development of a child. Universal hearing screening will help to detect congenital hearing loss by 3 months and intervention by 6 months of age. In infants OAE is the cheaper method used for hearing screening.

Major finding of the study was higher prevalence of hearing impairment in high risk babies. The risk weightage of expected frequency of babies found with Profound SNHL is not uniformly distributed. The number of babies found with Profound SNHL with high risk weightage is high compared to number of babies with low risk weightage. This can be used as criteria for referring babies for screening when selected babies can be screened due to resource constraints.

Compliance with Ethical Standards

Conflict of interest

Authors have no conflict of interest to disclose for the current study.

Human and Animals Rights

Only human were involved in the study.

Informed Consent

Informed consent was taken before doing the study from parents of the neonates.