Long-term developmental outcomes of early detection and intervention in Permanent Childhood Hearing Impairment

The DECIBEL-study
From January 2008 till December 2009, the Developmental Evaluation of Children:
Impact and Benefits of Early hearing screening strategies Leiden (DECIBEL) -
study defined the effects of the introduction of the Neonatal Hearing Screening
(NHS) on the overall development of hearing-impaired (HI) children in the
Netherlands. DECIBEL was a collaboration of the department of Pediatrics,
Otorhinolaryngology and Epidemiology of the Leiden University Medical Center.
The NHS was introduced gradually throughout the whole country starting in June
2002 and a full nationwide spread was accomplished in December 2005. The aim of
this early intervention system was to detect Permanent Childhood Hearing
Impairment (PCHI) at an early stage in life (i.e., preferably before the age of
three months) to be able to intervene and start treatment as early as possible
(i.e., before the age of six months) as advised by the Joint Committee on
Infant Hearing (JCIH). Because of the unique, stepwise introduction of the NHS,
this offered two naturally selected and unbiased groups; children screened
using the conventional (Ewing) screening method; and children screened with the
NHS. The place and date of birth of the child determined the type of hearing
screening offered.
Children suffering from congenital bilateral hearing loss of >=40 dB in the best
ear were invited to participate in the DECIBEL-study when they were 3-5 years
of age during the study period. Results of the DECIBEL-study showed better
overall, social and gross motor development, and quality of life in
hearing-impaired children age 3-5 screened using the NHS compared to the
conventional distraction hearing screening (DHS).

Socio-emotional development
For a long period of time research concerning hearing impairment in children
mainly focused on factors directly related to their hearing loss, such as
speech- and language problems. Support programs for children were built in
attempt to tackle these problems. Only recently the focus of research in HI
children is broadening and more attention is paid to the development of the HI
child as a whole. Research reveals that young HI children already show impaired
socio-emotional development. They encounter difficulties in recognizing and
understanding emotions in others and show a delayed Theory of Mind (ToM)
development. Research in older HI children (9-16 years old) has shown higher
levels of psychopathology such as depression, anxiety disorders and behavioral
problems. A possible explanation for these findings originates in the child*s
abilities to learn unintentionally and indirect. This is called incidental
learning (i.e., learning by experience and with no educational intentions) and
often implicates overhearing conversations between others with quick and snappy
dialogues. Missing the opportunity for this kind of learning will disadvantage
HI children. To optimise communication abilities, adequate language skills are
needed.
Studies on early intervention systems showed improvements in language and
communication skills as the child*s hearing losses were detected earlier and
intervention occurred at a younger age. Introduction of the NHS in the
Netherlands has enabled earlier detection of hearing loss. The percentage of
children that benefitted from the NHS (and in which intervention started
earlier) has been growing ever since. However, it is still unknown if early
detection in this cohort resulted in better speech- and language skills. We are
inquisitive to find out if HI children were better able to obtain higher skills
as their hearing impairment was treated earlier. We would like to define the
influence of these improved skills on their socio-emotional development.
Recent studies have shown that cochlear implantation during childhood has a
positive influence on many aspects of socio-emotional development compared to
the use of conventional hearing aids (HAs). However, scores still differ from
normal hearing (NH) children. Different types of educational settings have also
shown to influence developmental outcomes. HI children attending mainstream
schools performed better than those attending special education. This raises
questions about the role of the social environment of the HI child on its
development. Yet, we have to note that these studies were conducted in groups
of HI children that were born before introduction of early intervention
programs such as the NHS. So again the question rises if these differences
alter if children are rehabilitated at an earlier age.

Aim
1. To investigate the long-term effects of early detection and intervention of
hearing loss on the development of children with congenital bilateral hearing
impairment.
2. To define factors in early childhood that are able to predict developmental
problems later on in childhood, in order to create individualized
rehabilitation programs.

Objectives
1. What is the influence of early screening and intervention on the
socio-emotional, speech- and language development and academic achievement of
HI children?
2. Does early intervention lead to lower levels of psychopathology in HI
children?
3. Which factors in toddlerhood predict disturbed development in childhood?
4. What is the influence of different types and frequencies of intervention on
the socio-emotional and speech- and language development of HI children?
5. What is the long-term effect of early intervention on quality of life in HI
children?
6. Does early intervention lead to higher levels of empathy and prosocial
behavior in HI children?
7. How do hearing levels evolve during childhood?

Observational follow up of HI children in the pseudo-randomized DECIBEL-cohort.

The risks of taking part in this study are in our view negligible.
Participation in similar studies showed that children had fun completing the
different tasks and tests. To lower the effort to participate, children will be
visited at home or at school. Parents will be asked to complete several
questionnaires. This can be done either via a secured website or via a paper
version that can be replied to the study centre.