According to the Centers for Disease Control and Prevention (CDC), deafness (or hearing loss) happens when a side or the two sides of the ear is not working effectively. This makes the person partially or completely dependent on visual (rather than auditory) means of communication like sign language, reading/writing, speech reading, or lip-reading.
About 0.3% of 100 children are born with complete or partial deafness in one or both ears in the United States. This is according to the statistics collated by the National Institute of Deafness and Other Communication Disorders (NIDCD) as of March 2021.
Within these same statistics, it was reported that more than ninety percent (90%) of these kids were born to parents that were neither partially nor completely deaf. This raises the question, what causes a person to be born deaf?
What Causes A Person To Be Deaf?
According to the American Hearing Research Foundation, hearing loss (deafness) can come suddenly or gradually, and the causes can range from infections to side-effects of (some) medications, and aging.
Some studies have also suggested that there is a genetic background to deafness, confirming that about 50-60% of cases relating to deafness in babies are due to genetics.
How Is Deafness Inherited?
There are several forms of genetic mutations present at birth that can result in hearing loss. The American Academy of Otolaryngology-Head and Neck Surgery (on ENT Health organization) explained the different ways genes can transfer deafness within a family. These include the Mitochondrial inheritance, the X-linked inheritance method, the Autosomal dominant inheritance condition, and the recessive autosomal inheritance condition.
With all these ways that deafness can be inherited, you may be wondering if deafness can run in families. Yes, it can, especially if the parents do not have the proper awareness.
A parent has a twenty-five percent (25%) chance of passing a mutation to a child. From the X-linked inheritance, the result is usually sex-linked deafness that results from a mutation on the X chromosome.
This type of deafness is most often expressed in boys. Girls are not as affected, because two copies of the mutated gene that carry two X chromosomes are needed to cause deafness in girls.
More than seventy-five percent (75%) of inherited deafness cases have resulted from the Recessive autosomal inheritance condition while the autosomal dominant hearing loss is rare, and affects boys and girls in equal numbers.
Can Deaf Parents Have a Hearing Child?
Under the ‘Children of Deaf Adult (CODA)’ section of a 2018 study on the ‘Hearing Children of Deaf Parents’, it was recorded that approximately 5% of hearing children with deaf parents are born to two deaf parents. 10% were born to one deaf and one hearing parent. And as much as the child has no auditory disability, the common family language is usually sign language.
This occurs when a child is unable to receive the hearing condition through any of the different inheritance methods from the genes (paternal or maternal). But since it is usually a bit difficult to determine whether or not a child is deaf, it is important to undergo thorough evaluations with an Otolaryngologist (informally called an ear doctor), and an Audiologist.
These specialists are well equipped to identify co-morbid conditions (like speech and swallowing disorders), even in children. This way, they can prevent the child from having further growth and development problems.
Some of the early intervention services that could result from early diagnosis include speech therapy, hearing aids, and surgery for cochlear implants. Other services could be prescribed personally by the doctors/specialists.
What Type of Hearing Loss Is Hereditary?
There are some hereditary conditions in a parent that can be responsible for hearing loss in a child, such as Otosclerosis, Pendred Syndrome, and Usher’s Syndrome. The level of the condition dictates the type of hearing loss the child might suffer. However, there are two major different types of genetic hearing loss.
The first one is Sensorineural hearing loss (SNHL) that is caused due to impairment to the tiny hair cells in the inner ear. Though things such as age or diseases or even loud noise can cause this kind of hearing loss, genetics (inherited) is also a major reason.
If a mother suffered from rubella (also known as German measles) during pregnancy, a child could inherit Sensorineural hearing impairment. This condition doesn’t happen overnight but develops gradually in the child. Some of the symptoms include difficulty hearing voices or background sounds (especially lighter sound waves from a child, or high sounds like the clock ticking).
The second type of genetic hearing loss that can be hereditary is Conductive hearing loss. Although this is not a common hearing impairment, it is hereditary in a few cases.
Conductive hearing loss is also found to be temporary in some patients and curable. Some causes, other than genetics, of conductive hearing loss, includes blockage of the ear canal with wax. Otosclerosis can also be a major cause of this hearing loss.
In this type of situation, many find that bone conduction headphones are great for the hearing impaired, and allows them to listen to music without doing any further damage.
What Are the Side Effects of Hearing Loss?
According to the CDC, about 20-30% of the people born with inherited deafness are not free from other disabilities. They could suffer from developmental delays in different parts of their body system, including the musculoskeletal system, the neurological and optical system, the immune disorder system, and the cardiovascular system.
Many common disabilities that are associated with inherited deafness can affect a child’s everyday life, from school to making friends, to balancing.
Medically, genetic hearing loss can lead to vision abnormality, as well as blindness (partial or total). These disorders can develop gradually without many detecting them on time. On an advanced level, some studies have shown that deafness could result in heart disease or brain malfunction.
Can Deafness Skip a Generation?
Since it has been proven that deafness can be passed from parents to children, which means it has a high tendency of running in the family for a generation. You may wonder if deafness can skip a generation. Yes, it can.
A study by Harvard Medical School Center for Hereditary Deafness found out that even though deafness is hereditary, a child born from one (or two) deaf parent(s) may not be deaf depending on the level of hearing impairment present in the active X chromosomes of both parents.
The genetics of deafness (hearing loss) can be difficult to understand, especially from the layperson’s perspective. This article has helped to explain the basics of how deafness can be inherited. If at any point in time, you notice a symptom of hearing loss, report to your physician immediately. Don’t forget to share this information with friends and families to increase awareness.