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Prevalence of hearing impairment and language and cognition delay in very low birth weight babies and their risk factors

Chaudhuri, et al.: Prevalence of hearing impairment and language and cognition delay in very low birth weight babies and their risk factors Asian Journal of Medical Sciences | Dec 2021 | Vol 12 | Issue 12 63 Executive function and attention skills are suboptimal in most of the VLBW infants.9 The prevalence of impaired hearing in neonates with VLBW is significantly higher than in neonates with normal birth weight because of higher rates of transient middle ear fluid accumulation and conductive hearing loss. Long-term careful monitoring for hearing loss and their audiological management VLBW babies is essential.10 1.5% of the VLBW cohort was found to have abnormal prolongation of ABR waveform latency despite normal auditory thresholds, suggesting that even though cochlear function may have been normal; there may have been abnormal ascending brainstem pathways.11 Children with hearing loss may have difficulty with hearing and understanding sounds around them and thus leading to speech and communication disorder. Aims and objectives 1. To estimate the hearing and language and cognition delay among very low birth weight babies. 2. To identify the risk factors of language and cognition delay in VLBW babies. 3. To correlate the predictive value of language evolution at 1 year with language evolution at 2 years of age. 4. To correlate the predictive value of cognition evolution at 1 year with cognition evolution at 2 years of age. MATERIALS AND METHODS This is a prospective observational cohort study involving VLBW infants admitted in a level III Neonatal Intensive Care Unit (NICU) during the period of May to September 2016. All the infants discharged from NICU who were <1500 gram at birth were eligible for the study. The infants with chromosomal anomaly, major malformations and those who failed to attend for complete follow-up were excluded. Informed consent was obtained from the parents of VLBW infants eligible for the study. The study was pre-approved by the institutional ethics committee. Birth weight was taken just after delivery. Antenatal data were collected. Natal and subsequent management were done as per standard protocol. At 6 months of corrected gestation Developmental Assessment Scale for Indian Infants (DASII), 1 years of corrected age Bayley Scale of Infant and Toddler Development 3rd edition (BSIDIII) and 2 years of corrected age Receptive Expressive Emergent Language Test-3rd edition (REELS-3), was done by professionals who were unaware of case records (Figure 1). Hearing assessment was done by Oto Acoustic Emission and Screening Automate Auditory Brainstem Response before discharge. Diagnostic Brainstem Evoked Auditory Brainstem Response was done at 3 months of corrected gestation. Subsequent hearing assessment was done at 6 months and 1 year and 2 years of corrected gestation. Instruments and procedures DASII It is Indian adaptation of BSIDII. It is done up to 2.5 years of age. It has two scale: Mental and Motor. BSIDIII It is designed to assess the developing and high-risk infants and toddlers and young children aged between 1 and 42 months. It provides coverage of 5 domains: Cognitive, language, motor, adaptive, and social emotional development. REELS-3 It is used to identify disabilities, condition, impairment that may affect language development. Procedure takes 20 min for the children up to 3 years of age. Statistical analysis Linear correlation among two variables was calculated using Pearson correlation and then fit linear regression model to predict the response variables for a given covariate. Chisquare test of association was used to test significance of association between two categorical variables. Statistical software R was used here. Data had been summarised as mean and standard deviation for numerical variables and count and percentages for categorical variables and analysed by SPSS software version 24.0. Unpaired proportions were compared by Chi-square test or Fisher’s exact test as appropriate. Odds ratio was calculated for relative risk with 95% confidence interval value ≤0.05 was considered statistically significant.


INTRODUCTION
The prevalence of speech and language delays ranged from 5% to 8% at the age of 2-4.5 years, while studies of only language delays reported rates of 2.3-19%. Risk factors included a family history of speech and language delays, male sex, and perinatal factors, such as prematurity and low birth weight. 1 Based on the six studies in UK, the prevalence of speech and/or language delays in children ages 2-5 years to be between 5% and 12%. 2 Language delayed children may hold lower-skilled jobs and are more likely to be unemployed than unaffected children. 3 Approximately, 15 million babies are born very low birth weight, worldwide, each year. 4 Most of the very low birth weight babies are preterm. They have higher degree of language and social communication problems compared to full terms. [5][6][7][8] In about 40% of very low birth weight (VLBW) infants at school age, cognitive impairment had been reported.
Executive function and attention skills are suboptimal in most of the VLBW infants. 9 The prevalence of impaired hearing in neonates with VLBW is significantly higher than in neonates with normal birth weight because of higher rates of transient middle ear fluid accumulation and conductive hearing loss. Long-term careful monitoring for hearing loss and their audiological management VLBW babies is essential. 10 1.5% of the VLBW cohort was found to have abnormal prolongation of ABR waveform latency despite normal auditory thresholds, suggesting that even though cochlear function may have been normal; there may have been abnormal ascending brainstem pathways. 11 Children with hearing loss may have difficulty with hearing and understanding sounds around them and thus leading to speech and communication disorder.

Aims and objectives
1. To estimate the hearing and language and cognition delay among very low birth weight babies. 2. To identify the risk factors of language and cognition delay in VLBW babies. 3. To correlate the predictive value of language evolution at 1 year with language evolution at 2 years of age. 4. To correlate the predictive value of cognition evolution at 1 year with cognition evolution at 2 years of age.

MATERIALS AND METHODS
This is a prospective observational cohort study involving VLBW infants admitted in a level III Neonatal Intensive Care Unit (NICU) during the period of May to September 2016. All the infants discharged from NICU who were <1500 gram at birth were eligible for the study. The infants with chromosomal anomaly, major malformations and those who failed to attend for complete follow-up were excluded. Informed consent was obtained from the parents of VLBW infants eligible for the study. The study was pre-approved by the institutional ethics committee.
Birth weight was taken just after delivery. Antenatal data were collected. Natal and subsequent management were done as per standard protocol.
At 6 months of corrected gestation Developmental Assessment Scale for Indian Infants (DASII), 1 years of corrected age Bayley Scale of Infant and Toddler Development 3 rd edition (BSIDIII) and 2 years of corrected age Receptive Expressive Emergent Language Test-3 rd edition (REELS-3), was done by professionals who were unaware of case records ( Figure 1).
Hearing assessment was done by Oto Acoustic Emission and Screening Automate Auditory Brainstem Response before discharge. Diagnostic Brainstem Evoked Auditory Brainstem Response was done at 3 months of corrected gestation. Subsequent hearing assessment was done at 6 months and 1 year and 2 years of corrected gestation.

Instruments and procedures DASII
It is Indian adaptation of BSIDII. It is done up to 2.5 years of age. It has two scale: Mental and Motor.

BSIDIII
It is designed to assess the developing and high-risk infants and toddlers and young children aged between 1 and 42 months. It provides coverage of 5 domains: Cognitive, language, motor, adaptive, and social emotional development.

REELS-3
It is used to identify disabilities, condition, impairment that may affect language development. Procedure takes 20 min for the children up to 3 years of age.

Statistical analysis
Linear correlation among two variables was calculated using Pearson correlation and then fit linear regression model to predict the response variables for a given covariate. Chisquare test of association was used to test significance of association between two categorical variables. Statistical software R was used here.
Data had been summarised as mean and standard deviation for numerical variables and count and percentages for categorical variables and analysed by SPSS software version 24.0. Unpaired proportions were compared by Chi-square test or Fisher's exact test as appropriate. Odds ratio was calculated for relative risk with 95% confidence interval value ≤0.05 was considered statistically significant.

RESULTS
Under Linear Linear Regression Analysis, Shock, Perinatal Asphyxia, Hypoglycemia, and Cultutre Positive Sepsis showed significant correlation with Language development at 12 months of age (Table 1). After Multivariate Regression analysis only shock had significant correlation with language development at 12 months of corrected gestation (Table 2). Under Linear Regression Analysis Shock and Perinatal asphyxia got significant correlation with cognitive development at 12 months of corrected gestation (Table 1), but after multivariate regression analysis none of them showed significant correlation. Under Multivariate Linear Regression analysis only Shock had significant correlation with hearing assessment at 1 years of age (Table 3).
At 24 months of corrected gestation follow-up only 5 babies had language delay and 9 babies were at risk.
Correlation of DASII mental subscale score at 6 month with BSIDIII language subscale score at 12 months of corrected gestation We plot the scatter diagram of Mental 6 months with the language 1 year. The Pearson product moment correlation is 0.40 implying moderate linear correlation (Figure 2).

Correlation among BSIDIII language subscale at 12 months and REELS-3 language scale at 24 months
Correlation of language subscale at 1 year (assessed by BSIDIII) with 2 years language assessment done by REELS-3 is 0.59 and the scatter plot shown in Figure 3.

Correlation of cognition scale at 12 months of corrected age and cognition scale at 24 months of corrected gestation
Correlation between cognition 1 year and 2 year is 0.51 ( Figure 4).

DISCUSSION
3.4% of total preterm population in India are VLBW babies. Aram et al., 12 showed that a higher proportion of VLBW than control children had subnormal language associated with IQ <85, hearing deficits, after increased survival of preterm VLBW babies, there is in need of long term follow-up for language and hearing evolution in a resource limited settings.
In a study from South Africa on neurodevelopmental outcome of preterm infants with mean birth weight and mean gestational age of 1182 grams (SD: 197.78) and 30.81 weeks (SD: 2.67), The BSID III was done at a median age of 16.48 months. Out of 106 babies, 10 babies (9.4%) had language delay, 9 babies(8.5%) had cognition delay. 13 In our study population, the mean birth weight and mean gestational age were 1169.975 grams (SD: 244.3135) and 32.2 weeks (SD: 2.85) respectively and, 5 (7.8%) had language delay and 3 babies (4.7%) had cognition delay at 2 years (corrected gestation) of follow-up.
In our study, shock had got significant and consistent correlation with language and hearing impairment in    It is observed that there is a mild linear correlation between mental 6 months (DASII) with the cognition 1 year (BSIDIII) and the Pearson product moment correlation is 0.27.
The scatter diagram of Mental 6 months (DASII) with the language 1 year (BSIDIII) showed the Pearson product moment correlation is 0.40 implying moderate linear correlation. Specific terms and words expected from a child during the language test-not familiar to the Indian child resulted in lower scores and significant discrepancy.
Tomasik showed that Preterm VLBW babies have higher chances of hearing loss that term babies. Risk is further aggravated by Shock. 15 We are also getting strong correlation with shock and hearing impairment in VLBW babies.

Limitations of the study
There was good compliance up to 12 months of corrected age but at 24 months of corrected age there was 50% lost to follow-up.

CONCLUSION
Among the all antenatal and natal and postal risk factors neonatal shock and perinatal asphyxia has got most significant correlation with language, hearing and cognition. 6 months assessment of DASII has mild correlation with cognition subscale and moderate correlation with Language Subscale of BSIDIII (assessed at 12 months of corrected gestation). However, 12 months BSIDIII assessment of both the subscale has significant correlation with 24 months assessment.