Language and Speech Disorders Related to Hearing Loss

Among the factors that hinder language and speech development, hearing loss undoubtedly plays a major role because one of the most essential requirements for healthy language and speech development is healthy hearing. Due to its nature, hearing loss causes delays and deficiencies in a child’s language and speech development. Therefore, the early diagnosis of children with hearing loss and directing both the child and the family to appropriate educational support are extremely important. Otherwise, difficulties in language and speech development may arise, bringing along a range of problems from learning difficulties and self-esteem issues to academic failure and communication problems.

The language and speech problems experienced by individuals with hearing loss may vary depending on many factors such as the onset time of hearing loss, its type, the age at diagnosis, its severity, whether the child uses hearing aids or cochlear implants, the age at which hearing aids and/or cochlear implants are introduced, and the type of education received. As a result, insufficient and/or incomplete auditory input leads to delays and difficulties in language and speech development.

The Effect of Hearing on Language and Speech Development

Hearing is one of the indispensable factors for the development of language and speech. Hearing begins while the baby is still in the womb at around 20 weeks of gestation. In other words, a typically developing baby is born with approximately 20 weeks of auditory experience. Therefore, although information regarding language and speech development generally focuses on the postnatal period, babies already react to certain sounds while in the womb and can distinguish their mother’s voice from others. Thus, even before birth, auditory centers are stimulated through acoustic information, and auditory neural pathways begin to organize.

Acoustic information plays a critical role in helping children distinguish the speech sounds of the language spoken around them, forming their phonetic repertoire and, consequently, supporting language development through vocabulary acquisition.

What Is Hearing Loss and What Are Its Types?

Hearing loss refers to the loss of hearing resulting from damage occurring in the outer ear, middle ear, inner ear, and/or auditory pathways, either congenitally or after birth (before or after language acquisition). Depending on the affected part of the ear, hearing loss is classified as conductive hearing loss, sensorineural hearing loss, or mixed hearing loss.

Additionally, hearing loss is classified by degree as follows:

26–40 dB: Mild hearing loss

41–55 dB: Moderate hearing loss

56–70 dB: Moderately severe hearing loss

71–90 dB: Severe hearing loss

91 dB and above: Profound hearing loss

What Causes Hearing Loss?

The causes of congenital hearing loss can generally be divided into two categories: genetic and non-genetic factors. Non-genetic factors account for approximately 25% of cases, while genetic factors account for about 50%.

Non-genetic factors include infections during pregnancy such as rubella and herpes simplex virus, premature birth, low birth weight, birth trauma, use of toxic medications or alcohol during pregnancy, blood incompatibility, gestational diabetes, toxemia during pregnancy, and oxygen deprivation.

Hearing loss related to genetic factors may be present at birth or may develop later. Hearing loss may also occur in certain syndromic conditions such as Down syndrome, Usher syndrome, Treacher Collins syndrome, Crouzon syndrome, Alport syndrome, and Waardenburg syndrome.

In addition, chronic middle ear infections, use of ototoxic medications, meningitis, measles, encephalitis, chickenpox, influenza, mumps, head trauma, and acoustic trauma may also lead to hearing loss.

Language and Speech Development in Children with Hearing Loss

Phonological Development

Pre-linguistic Period

Until approximately 6–7 months of age, no significant differences are observed in vocal development between typically developing infants and infants with hearing impairment. Babies show similar development during the stages of phonation, cooing, and vocal play. However, when the canonical babbling stage begins, reductions in babbling are observed in hearing-impaired infants if auditory feedback is absent.

Word Level

Considering factors such as the type and severity of hearing loss and the age at diagnosis, delays are commonly observed during the first-word stage compared to typically developing peers. While typically developing children generally have a vocabulary of around 50 words by the age of 1–1.5 years, many children with hearing loss may not yet have transitioned to the single-word stage, and some may not use spoken language at all.

Some children may initially show language development similar to their peers, but over time their vocabulary growth increasingly lags behind.

Morphological and Syntactic Development

Children with hearing loss tend to prefer short and simple sentences and understand these more easily. They may struggle to understand and produce complex sentence structures such as relative clauses and passive constructions.

They are reported to use structures like subject-object-verb more frequently, while using prepositions, auxiliary verbs, and conjunctions less often. Due to difficulty hearing word endings, they may omit or misuse grammatical markers such as tense suffixes, plural endings, subject-verb agreement markers, and possessive suffixes. They may also have difficulty acquiring these grammatical structures.

Semantic Development

Children with hearing loss generally have a limited vocabulary. They may learn abstract words more slowly than concrete words. They often struggle to understand and appropriately use figurative language, idioms, metaphors, and words with multiple meanings.

Pragmatic Development

Difficulties may be observed in conversational initiation and maintenance strategies, diversity of communicative intentions, changing or ending conversation topics, and repairing communication breakdowns effectively.

Acquisition of Speech Sounds

During the first six months, infants can distinguish many sounds not present in the language spoken around them. By the end of the first year, phonetic categories reorganize to match the sounds of their native language.

Insufficient auditory information prevents individuals with hearing loss from hearing certain speech sounds and/or distinguishing features that differentiate one sound from another. As a result, speech intelligibility may be reduced. They may not hear their own voice clearly and may struggle to regulate vocal loudness. Due to weaknesses in intonation, stress patterns, or speech rate, their speech may sound muffled or monotone.

Overall, the language and speech development profile described above is commonly observed in individuals with hearing loss. However, with the increasing use of cochlear implants in recent years, it has been reported that many individuals with hearing impairment demonstrate developmental patterns more similar to their typically developing peers.

The Role of the Speech and Language Therapist

The group referred to as “individuals with hearing impairment” is highly heterogeneous, making generalizations difficult. Therefore, teamwork becomes especially important when creating education and therapy plans for each individual.

This team may include professionals such as teachers of the hearing impaired, audiologists, speech and language therapists (SLTs), and psychologists.

SLTs have expertise in communication effectiveness, communication disorders, differences, and delays that may arise due to hearing impairment and related factors. They can provide support regarding normal communication development, communication development affected by hearing impairment, assessment of communication skills, therapy processes, and prevention of communication-related problems in individuals with hearing loss.

SLTs play an active role in evaluating and diagnosing language development (phonology, morphology, syntax, semantics, pragmatics) and speech development (articulation, resonance, respiration), providing necessary therapy support, and supporting pre-literacy and language-based reading skills such as phonological awareness as part of a multidisciplinary team.