Researchers have found that bilateral tinnitus can have genetic causes and that some kinds of tinnitus can be hereditary. This finding is surprising because tinnitus has conventionally been thought only to be driven by environmental factors.
Prevalence, severity of tinnitus in the US
Tinnitus is a symptom characterized by the perception of sound in the absence of an external stimulus. It is often described as “ringing in the ears” and approximately one in 10 adults in the US have tinnitus. If persistent and intolerable or sufficiently bothersome, tinnitus can cause functional impairment in thought processing, emotions, hearing, sleep, and concentration, all of which can substantially and negatively affect quality of life.
Tinnitus prevalence increases with age and is thought to be related to a number of environmental factors but little research has been done on the subject. There are also no effective cures for the condition, due possibly to the heterogeneity of the condition.
An unexpected finding
A study from the Swedish Karolinska Institutet showed that bilateral tinnitus – that is, tinnitus in both ears – can have a significant heritability and thus in some cases genetics influence tinnitus as well as environmental factors. The study also showed that the prevalence of hereditary, bilateral tinnitus is greater among men than women.
Initially, the researchers of Karolinska Institutet did not find any unusual results concerning the heritability of tinnitus. They only discovered the genetic correlation after grouping the subjects by sex and unilateral/bilateral tinnitus.
“This result is surprising and unexpected as it shows that, unlike the conventional view of tinnitus being driven by environmental factors, there is a genetic influence for bilateral tinnitus which is more pronounced in men,” says Christopher R. Cederroth of Karolinska Institutet’s Department of Physiology and Pharmacology.
About the study
The study was conducted by examining data from 10,000 twin pairs from the Swedish Twin Registry comparing the prevalence of tinnitus among twins who are respectively identical and fraternal. A greater concordance of tinnitus among identical twins than among fraternal twins implies a genetic correlation, and this was the case of bilateral tinnitus in the study. However, no correlation in the study was found concerning unilateral tinnitus – that is, tinnitus in one ear.
The study “Genetic susceptibility to bilateral tinnitus in a Swedish twin cohort” was published in Genetics in Medicine.
Sources:www.sciencedaily.com and Genetics in Medicine