Hearing in Down Syndrome

Definition and epidemiology

Down syndrome (trisomy 21) is one of the genetic conditions most often associated with hearing loss. The loss has three sources: narrow ear canals with wax build-up, middle ear effusion and ossicular anomalies, and sensorineural loss of inner ear origin. These components can coexist in one person and change with age. Conductive loss predominates in childhood, while in adulthood sensorineural loss begins much earlier than in the general population.

In a study of 344 babies with Down syndrome born in Utah, 26.2% did not pass newborn hearing screening; of these, 37.9% had conductive loss from effusion, five had sensorineural and three had mixed loss (Park et al., 2012). At a Belgian Down syndrome clinic, otitis media with effusion reached 66.7% at age 1 and peaked again at 60% at ages 6-7 (Maris et al., 2014). In a Dutch study of 1598 adults with intellectual disability, Down syndrome increased the risk of hearing loss about fivefold (OR 5.18), and all adults with Down syndrome over 60 had hearing loss (Meuwese-Jongejeugd et al., 2006).

Symptoms and signs

The commonest picture in childhood is a mild to moderate conductive loss from otitis media with effusion. Children with bilateral effusion had a median hearing threshold of 36.7 dB HL, compared with 28.3 dB HL in those with at least one normally ventilated middle ear (Maris et al., 2014). Effusion is often silent and is noticed only as reduced responses to sound, inattention or regression in speech, without pain or fever. Because speech and language development in Down syndrome is already slower, these signs are easily attributed to the syndrome itself.

More than 43% of babies who passed newborn screening later developed conductive loss needing ventilation tubes, and among babies who did not pass and were found to have sensorineural loss, diagnosis was delayed by an average of 485 days (Park et al., 2012). A normal newborn screen therefore does not mean hearing will stay normal. Sensorineural and mixed losses tend to progress over time, whereas conductive loss tends to improve, especially when the first tubes are placed before age 2 (Kreicher et al., 2018).

In adulthood sensorineural loss starts early. Among 72 adults with Down syndrome (mean age 37), hearing loss was found in 65.3%, rising from 42.9% at 20-29 years to 90.9% at 50-59 years, with 4 kHz most affected (Picciotti et al., 2017). The age-related rise has been estimated to begin about three decades earlier than in the general population (Meuwese-Jongejeugd et al., 2006).

Causes and risk factors

Middle ear problems stem from underdevelopment of the midface and Eustachian tube dysfunction. Chronic rhinitis, sinusitis and frequent upper respiratory infections also help effusion persist and contribute to chronic ear infections (Shott, 2006). Narrow ear canals make it harder for wax to clear naturally and increase the tendency to earwax impaction; a narrow canal also makes the eardrum and middle ear harder to examine.

The main cause of the sensorineural component is early ageing of the inner ear. The premature ageing seen in many organ systems in Down syndrome also affects hearing, producing a high-frequency pattern similar to presbycusis but starting decades earlier (Picciotti et al., 2017). Recurrent infections, chronic otitis media and cholesteatoma can also cause permanent conductive or mixed loss; conductive loss is more likely to improve in children without cholesteatoma (Kreicher et al., 2018).

Audiological and clinical assessment

Because hearing loss in children with Down syndrome is common, silent and fluctuating, assessment is carried out at regular intervals rather than waiting for symptoms. The 2022 health supervision report of the American Academy of Pediatrics (AAP) treats follow-up of the newborn hearing screen result and regular hearing assessment through childhood and adolescence as part of health supervision (Bull et al., 2022). Park et al. (2012) showed that 84% of newborns with Down syndrome who missed screening never had any later hearing test; loss to follow-up is one of the main problems in this group.

• Otoscopy: the eardrum often cannot be seen because of a narrow canal and wax. Measurements made before the canal is cleared are misleading; if needed, the child is referred to an ENT surgeon for microscopic cleaning and examination.
• Tympanometry: effusion gives a flat (type B) trace. In a narrow canal a low ear canal volume can be confused with the probe tip resting against the canal wall, so small probe tips should be used. In infants a high-frequency (1000 Hz) probe tone is preferred.
• Visual reinforcement audiometry and play audiometry: as developmental age may lag behind chronological age in Down syndrome, the method is chosen by developmental age; responses may be slower and less consistent, and testing can be split into several short sessions.
• ABR: when ear-specific behavioural thresholds cannot be obtained, air- and bone-conduction ABR establish the type and degree of loss. If sedation or anaesthesia is needed, airway problems and sleep apnoea must be considered (Shott, 2006).
• OAEs: effusion and wax can abolish OAEs, so absent OAEs alone are not evidence of sensorineural loss; in screening and monitoring they are interpreted together with tympanometry.

In adults, hearing should be monitored with pure-tone and speech testing every year or at least periodically, recording early changes at 4 kHz and above (Picciotti et al., 2017). The adult care guideline recommends starting screening for Alzheimer-type dementia at age 40 (Tsou et al., 2020). Because hearing loss can cause withdrawal, difficulty following instructions and disengagement that mimic dementia, the ear canals and hearing must be checked before cognitive assessment.

Treatment and audiological rehabilitation

Otitis media with effusion lasts longer and recurs more often in children with Down syndrome than in other children. The decision on ventilation tubes rests with the ENT surgeon; a narrow canal makes insertion and follow-up harder, and tubes may need replacing more often. Regular ear examination continues to watch for cholesteatoma and chronic otitis media. When conductive loss is likely to persist, temporary amplification can be considered rather than waiting through the critical period for language.

Persistent loss is managed with hearing aid fitting. A narrow, tortuous canal makes it harder to take impressions, seat the earmould and prevent feedback; soft mould materials, receiver options suited to small canals and frequent remakes are needed. Wax reduces the output of the aid, so checking the wax guard and regular ear cleaning are built into the plan. If recurrent discharge or a very narrow canal rules out an air-conduction aid, bone conduction devices and bone conduction implants are options. Real-ear measurement (REM) is particularly important because the acoustics of a narrow canal differ from average values.

Success depends on the aid being worn all day. Tactile sensitivity and removing the aid are common; a programme that starts with short periods and extends them with positive reinforcement should be followed together with family and teachers. At school a remote microphone system makes listening in noise easier. In adulthood, hearing aid fitting should be planned together with training carers to insert and clean the aid and change batteries.

Impact on quality of life and advice

Speech and language develop more slowly in children with Down syndrome, and even an unnoticed mild conductive loss can deepen this delay and harm attention and learning. At school, noisy classrooms combine hearing loss with difficulties in auditory attention and memory. In adulthood, early-onset hearing loss reduces social participation, can lead to loneliness and withdrawal, and may be confused with signs of dementia.

Practical advice: keep up your child’s regular hearing checks, even if they passed the newborn screen. When talking, make sure your child can see your face, use short, clear sentences and support them with signs and gestures. Do not clean the ears with cotton buds; in a narrow canal wax is pushed deeper. Start with short periods of hearing aid use and build up gradually. If you notice a change in behaviour in an adult relative, ask for a hearing test among the first investigations; correcting hearing loss can markedly improve communication and quality of life.