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Mitochondrial DNA Haplogroups and Age-Related Hearing Loss
Neil Manwaring, PhD;
Michael M. Jones, MBBS;
Jie Jin Wang, MMed, PhD;
Elena Rochtchina, MApplStat;
Chris Howard, BBiotech(Hons);
Phillip Newall, MSc(Sur), MSc(Salf);
Paul Mitchell, MD, PhD;
Carolyn M. Sue, MBBS, PhD
Arch Otolaryngol Head Neck Surg. 2007;133(9):929-933.
Objective To determine whether variants of the mitochondrial genome influence the risk of developing age-related hearing loss (ARHL).
Design Cross-sectional study.
Setting Eligible participants were noninstitutionalized permanent residents 49 years or older identified in a door-to-door census of 2 suburban postcode areas, west of Sydney, Australia.
Participants The Blue Mountains Hearing Study (BMHS) was a population-based survey of hearing loss, conducted during 1997 to 1999, among the participants of the Blue Mountains Eye Study cohort.
Main Outcome Measures We defined hearing impairment as the pure-tone average of audiometric hearing thresholds at 500, 1000, 2000, and 4000 Hz (> 25- but  40-dB hearing level [HL] [mild hearing loss], > 40- but 60-dB HL [moderate hearing loss], or > 60-dB HL [severe hearing loss]) in the better of the 2 ears.
Results Of the 2765 BMHS participants, 912 (33%) were found to have ARHL. After adjusting for other hearing loss risk factors, mitochondrial DNA (mtDNA) haplogroups U and K were independently associated with a higher prevalence of ARHL compared with subjects with other haplogroups. Haplogroup U was significantly associated with moderate to severe ARHL (multivariable-adjusted odds ratio, 1.63; 95% confidence interval, 1.10-2.41). Haplogroup K was associated with severity types of ARHL in persons aged 50 to 59 years (odds ratio, 3.02; 95% confidence interval, 1.30-6.99). There was also a joint effect between mtDNA haplogroups U and K and other known hearing loss risk factors such as diabetes and past noise exposure.
Conclusion Findings from this older Australian population demonstrate an association between certain mtDNA haplogroups and ARHL, as well as a link to the susceptibility of other known risk factors for ARHL.
Author Affiliations: Department of Neurogenetics, Kolling Institute (Drs Manwaring, Jones, and Sue and Mr Howard), and Department of Ophthalmology, Centre for Vision Research, Westmead Millennium Institute (Drs Wang and Mitchell and Ms Rochtchina), University of Sydney, and Department of Linguistics, Macquarie University (Mr Newall), Australia.
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