Tinnitus or ringing in the ears is the perception of sound which is not externally present. In other words, it is a perceived phantom sound that only the afflicted individual can hear. It affects about 15% of the global population and 50 million individuals in the United States. The quality of life is severely affected in 3-6% of those who suffer from it as it can be chronically bothersome, debilitating and incapacitating. It varies from person to person, with some reporting that they hear beeping, hissing, ringing, buzzing, roaring, and even drumming sounds. Tinnitus can be:
- Objective (generated by the ear and can be perceived by others)
- Subjective (only heard by the affected individual)
- Constant or intermittent
- Loud or faint
- Perceived in one ear or both ears
From the social point of view, tinnitus causes productivity loss and heightens the risk of receiving disability. It is most commonly associated with exposure to loud noises which causes injury to the hair cells in the ear. It is also associated with other conditions such as:
- Temporomandibular joint issues
- Brain tumors
- Head or neck injuries
- Thyroid dysfunction
- Ototoxic medications
- And more.
Many of those suffering from tinnitus also report other symptoms such as anxiety, poor concentration, irritability, depression, insomnia, and hyperacusis (lowered tolerance to loud noises). It can be categorized according to:
- Psychoacoustic features
- Level of severity
- Psychological distress
- Daily life disability
It can also be assessed based on the duration of symptoms where:
- Less than 3 months = acute
- 3 to 12 months = subacute
- More than 1 year = chronic
Currently, there are no effective drugs that are used for the treatment and management of tinnitus. The standard for management of tinnitus aims to reduce the symptoms of tinnitus to allow the patients to live a more comfortable and less disrupted life. Researchers have attributed the lack of success in treatments to the heterogeneity of conditions that are associated with tinnitus. Genetic studies could help with the identification of subgroups of tinnitus to optimize treatment outcome and provide targets for drug development.
Genetics in Tinnitus
Tinnitus have been reported to occur in clusters of families but to this day, the importance of genetics in tinnitus is still barely known as research is still its infancy. As with all topics, there is literature that supports that:
Tinnitus is not hereditary (or plays an insignificant role)
A study conducted by a Norwegian research team, headed by Dr. Ellen Kvestad suggests that there is little to no chance of a genetic connection to tinnitus. This extensive study involved a large number of participants totaling to more than 52,000 people (13,000 spouses; 27,000 parents and their children; 11,498 siblings). The participants receive a questionnaire that asks them tinnitus and its symptoms. They also underwent a hearing examination. From this group (52,000 people), approximately 34,000 had some degree of hearing loss. This group was then presented with a second set of questions and 28,066 questionnaires were returned. After the analysis of results, the research team found that there was no indication of tinnitus being passed down through their families. However, the data did not distinguish between the possible types of tinnitus and the team recommends that the result to be replicated with subtypes of tinnitus and other types of family data. Another study in 2007 that studied 198 families also concluded that there is no obvious heritability.
Tinnitus is hereditary
In a recent study that was published in 2017, researchers were able to demonstrate the significance of genetics in certain forms of tinnitus. The twin study that was published in the journal Genetics in Medicine was a joint effort between researchers from the Karolinska Institutet and the European research network. The researchers at Karolinska Institutet used data from the Swedish Twin Registry and were able to demonstrate that there is significant hereditability in different forms of tinnitus and how the genetic influence dominates over environmental factors. A total of 70,186 twins submitted their answered questionnaires to the team with 10,464 pairs of twins (one or both affected) who experience tinnitus. The team was only able to see the correlation after grouping the participants by gender and unilateral or bilateral tinnitus. From their findings, they concluded that bilateral and unilateral tinnitus are two different subtypes where only the bilateral tinnitus is influenced by hereditary factors and is more common among men compared to women. The value they obtained is close to the levels of heritability for other disorders such as schizophrenia and attention deficit hyperactive disorder (ADHD).
Other genetic mutations that have been linked to tinnitus are associated with other underlying diseases such as neurofibromatosis type II (NFII) and von Hippel-Lindau disease. Although more research is needed to establish the contribution of genetics, current findings have opened the possibility of certain types of tinnitus to be more hereditary compared to others. Since familial tinnitus is rare, the study of afflicted families is a potential strategy for the discovery of genes that are involved in tinnitus. The highly unmet clinical needs of tinnitus cause the recent identification of possible genetic factors to be an exciting opportunity for researchers. The discrepancies of these various findings indicate that more research should be conducted before a final verdict is made regarding the role of genetics in tinnitus. The dissimilar conclusions drawn from various studies may be due to the different designs and formulations of the questionnaires used.
Conclusion About Genetics in Tinnitus
Based on current literature and findings, your susceptibility to tinnitus is most likely due to a combination of genetic and environmental factors such as age, lifestyle habits, exposure to noise, and more. So far, bilateral tinnitus has been found to have a genetic component while other research has not been able to find little to no genetic component in general cases of tinnitus. The final verdict regarding the role of genetics in tinnitus is still yet to be determined but with recent finding, researchers hope to conduct more studies to further their understanding of tinnitus.