Genetic variation linked to age-related hearing loss
A team of NIH-supported researchers has confirmed a link between age-related hearing loss and a gene producing a key protein in the inner ear. The findings reinforce observations in older people that genetics and environment interact, linking age-related hearing loss to other neurodegenerative risk factors. Results of the nine-year study were published online on October 25, 2012, in Hearing Research.
The study confirms the genetic association and, for the first time, establishes a link between a gene and difficulties with speech perception in older people. Previous research in a large group of older adults in Europe had identified a significant risk factor associated with age-related hearing impairment (ARHI) in the glutamate metabotrophic receptor 7 (GRM7) gene.
The research team analyzed data from 687 individuals (59 percent female) from the Rochester, New York, greater metropolitan area. All study participants were white, with an average age of 71 and not related to anyone else in the study. Participants had a wide range of hearing abilities and underwent extensive standard and specialized assessments of hearing. Importantly, the researchers conducted tests of speech reception thresholds (SRTs) as well as pure-tone thresholds (PTs). DNA was taken from blood or tissue samples.
Clinically, PTs are used to measure the basic level of hearing ability and sensitivity to sounds. But they do not indicate how well a person can perceive and process speech, which is a significant problem for older people with hearing loss. Deficits in speech detection can detract from productivity, quality of life, and psychological well-being for older people.
The study results show that GRM7 is significantly associated with PT and SRT. This is the first investigation of genetic associations with measures of speech perception in older adults, supporting the role of GRM7 contributing to age-related hearing loss and speech perception.
ARHI, also known as presbycusis, is one of the top three chronic medical conditions of older people, along with high blood pressure, and arthritis. More than 37 percent of people 65 and older report some trouble hearing; this increases to almost 59 percent in people 85 and older. Many older people find it difficult to adapt to hearing loss; this can result in communication difficulties at work and at home, leading to psychological problems, isolation and depression.
Reference: Newman DL, et al. GRM7 variants associated with age-related hearing loss based on auditory perception, Hearing Research (2012). http://dx.doi.org/10.1016/j.heares.2012.08.016