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Chromosome Region Implicated in Age-Related Hearing Loss

JAMA - ChicagoA region on chromosome 3 that has been linked to a form of progressive hereditary hearing loss in younger adults may also be associated with hearing loss in elderly men, according to an article in the May issue of the Archives of OtolaryngologyHead & Neck Surgery, one of the JAMA/Archives journals.

Hearing loss is the most common sensory disorder around the world, and hearing loss associated with aging affects about 25 to 30 percent of adults age 65 years and older, according to background information in the article. A study of Danish twins suggested that age-related hearing loss was at least 40 percent heritable, but few studies have looked at specific genetic factors that might influence its development.

Holly J. Garringer, B.S., Indiana University School of Medicine, Indianapolis, and colleagues assessed 50 pairs of elderly male fraternal twins (average age 74.3). All participants answered questions about their hearing and provided a blood sample that the researchers used to develop a genotype, or genetic profile, of each individual. Only pairs of twins in which both siblings reported hearing loss were included in the study. Because siblings inherit one copy of each gene from each of the same two parents, they can share either two identical copies, one identical copy or no identical copies of each gene. If a gene or area on a chromosome is linked to a trait that siblings share-in this case, age-related hearing loss-the siblings would be expected to have more identical genetic material in that area than in areas containing genes for traits that the siblings do not share.

The authors analyzed 400 genetic markers for hearing loss-genes whose locations have been pinpointed and some functions understood. They found evidence of genes linked to age-related hearing loss on chromosome 3q, near a gene locus (location) known as DFNA18. This locus is thought to contain a gene that causes early-onset autosomal dominant hearing loss, a condition that begins earlier in life and continues for decades.

Additional information is needed to understand exactly which gene contributes to age-related hearing loss and whether the same gene could be responsible for both age-related and early-onset conditions. If these early results are confirmed in later studies, it is possible that other variations in genes in or near the DFNA18 locus "might be responsible for a substantial percentage of hearing loss with aging in the general population," the authors conclude.

Arch Otolaryngol Head Neck Surg. 2006;132:506-510
archotol.ama-assn.org/cgi/content/short/132/5/506

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