DNA Can Reveal Your Adult Onset Hearing Difficulty
Some types of adult onset hearing difficulty may have a genetic component. Knowing your genetic risks for hearing loss may help you take the steps necessary to protect your hearing with simple lifestyle changes. Getting regular hearing tests and speaking to your doctor about your risks may also help you care for your auditory health.
What Challenges Accompany Adult Onset Hearing Difficulty?
Adult-onset hearing difficulty is the most common sensory impairment characterized by a non-syndromic bilateral, sensorineural hearing loss in the aging population. Nearly a third of individuals are affected by disabling hearing loss by the age of 65. Hearing loss in adults can lead to adverse mental health conditions, such as social isolation and depression, and it has recently been identified as a risk factor for dementia. Despite the seriousness of this impairment, hearing amplification devices are the only treatment option currently available for adult-onset hearing difficulties.
How Does Mild Hearing Loss Develop?
There are several potential causes of hearing loss. Aging causes wear and tear on the nerve cells and hairs responsible for sending sound signals to the brain. Other causes include:
- Overexposure to loud or high-pitched noises
- Earwax buildup
- Ear infection
- Tumors or unusual bone growth in the ear
- Ruptured eardrum
- Some medications
Heredity can also play a role in hearing loss. Your genetic makeup could put you at a higher risk for developing a hearing deficit.
Defining Auditory Phenotypes
There are three main types of adult hearing loss: conductive, sensorineural, and mixed. Conductive hearing loss can be caused by blockages in the ear canal. In some cases, this type of hearing loss can be repaired with surgery or medical intervention. Sensorineural hearing loss is the most common type of hearing loss. It typically results from aging but can be caused by injury, disease, or noise exposure. Hearing aids can help. Mixed hearing loss can occur when someone has sensorineural hearing loss and then develops a conductive component. A combination of hearing aids, surgery, or medical intervention may be effective.
Examining a Breakthrough Study: Unlocking the Genetic Secrets of Age-Related Hearing Difficulty
From a genetic perspective, adult onset hearing difficulty is expected to be a highly heterogeneous trait given that more than 150 genetic loci have been identified in non-syndromic congenital hearing loss alone. To date, however, five genomic loci have been significantly associated with adult hearing difficulties in previous genome-wide association studies (GWASs), only two of which were replicated in independent population samples. Understanding the genetic etiology of adult-onset hearing impairment may shed some light on the pathophysiology of the condition and ultimately facilitates the development of novel therapeutic or preventative interventions.
In this context, researchers performed a GWAS for two hearing phenotypes: hearing difficulty (HDiff) and hearing aid use (HAid). Participants included volunteers in the UK Biobank (UKBB) aged between 40 and 69 years. UKBB participants were categorized using a case-control design based on responses to questions regarding HDiff and HAid.
HDiff case subjects responded ‘‘Yes’’ to both of the questions ‘‘Do you have any difficulty with your hearing?’’ and ‘‘Do you find it difficult to follow a conversation if there is background noise (such as TV, radio, children playing)?’’ HDiff control subjects were selected if their response to both of these questions was ‘‘No.’’ Participants with any other combination of responses were removed. Up to 500,000 samples in UKBB were genotyped and a total of 250,389 samples (87,056 case subjects and 163,333 control subjects) were used for association analysis of HDiff. Forty-four independent genome-wide significant SNP associations were identified.
Two independent associations were found near the ARHGEF28 locus, which is a novel finding. It represents a more than 400-fold increase in the number of reported genome-wide significant SNP associations and a 9-fold increase in independent genomic loci for age-related phenotypes and provides a major breakthrough in revealing the genetic architecture of ARHI
The gene encodes for Rho Guanine Nucleotide Exchange Factor 28 which has been suggested to be involved in neuronal function or maintenance. While ten loci have previously been linked to some form of hearing loss either in mouse models or humans. Other SNPs near ARHGEF28 and EYA4 were also associated with HAid.
One of the limitations of the study is that the age of onset of HDiff or HAid prescription was not confirmed, making an accurate diagnosis of adult hearing difficulty challenging. In this study, in order to lower the possibility to include individuals with congenital hearing impairment in the case subject, a minor allele frequency cut-off of 0.01 (i.e., higher than the known frequency of variants involved in congenital deafness) and by excluding participants who selected ‘‘I am completely deaf’’ in the UKBB questionnaire.
To sum, the new findings in the study using large cohorts such as UKBB provide therapeutic opportunities in age-related hearing difficulty and possibly dementia. Read more about the study here: https://www.ncbi.nlm.nih.gov/pubmed/31564434
What Is Your Genetic Risk for Hearing Loss?
Don’t wait until you begin having hearing problems to learn what your DNA can reveal about your risks. Upload your raw DNA data to Genomelink and find out now. The more you know, the better prepared you will be to take preventative action.
Are you interested in learning more about your genetic tendency for adult-onset hearing difficulty? You can login to your Genomelink dashboard to see this new genetic trait.
Photo by Hayes Potter on Unsplash
