Feb 152011

From Could Hearing Aids Delay Dementia?

Reuters Health 2/14/11  http://news.yahoo.com/s/nm/20110214/hl_nm/us_hearing_aids

“Dementia is devastating, and the prevalence doubles every 20 years,” said Dr. Frank R. Lin, an ear surgeon at Johns Hopkins University in Baltimore, whose findings appear in the Archives of Neurology.

“There are some studies showing that if you can delay dementia onset by just one year, you would decrease the prevalence of dementia by more than 10 percent in 2050.”

With funding from the National Institute on Aging, Lin and colleagues followed more than 600 men and women over an average of 12 years. All had a hearing test done at the outset of the study; none was demented at that point.

Overall, 9 percent of the participants developed some type of dementia during the study, most commonly Alzheimer’s disease. And the worse their hearing, the greater their risk.

Those with mild hearing loss, which can make it hard to follow a conversation in a noisy restaurant, had nearly twice the chance of developing dementia compared to people with normal hearing — even after ruling out the influence of age and other factors.

The risk increased three-fold for those with moderate hearing loss and five-fold for severe impairment.

“Does it mean you will develop dementia if your hearing is impaired?” Lin said. “Absolutely not! But is your risk increased? You betcha.”

Lin said one small study from the 1980s had reached similar conclusions, but that the new study was the first to follow people over time.

What’s responsible for the link is still unclear, however.

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Hearing Loss and Incident Dementia

From Archives of Neurology, Vol. 68 No. 2, February 2011


Frank R. Lin, MD, PhD; E. Jeffrey Metter, MD; Richard J. O’Brien, MD, PhD; Susan M. Resnick, PhD; Alan B. Zonderman, PhD; Luigi Ferrucci, MD, PhD

Arch Neurol. 2011;68(2):214-220. doi:10.1001/archneurol.2010.362

Objective To determine whether hearing loss is associated with incident all-cause dementia and Alzheimer disease (AD).

Design Prospective study of 639 individuals who underwent audiometric testing and were dementia free in 1990 to 1994.Hearing loss was defined by a pure-tone average of hearing thresholds at 0.5, 1, 2, and 4 kHz in the better-hearing ear (normal, <25 dB [n = 455]; mild loss, 25-40 dB [n = 125]; moderate loss, 41-70 dB [n = 53]; and severe loss, >70 dB [n = 6]). Diagnosis of incident dementia was made by consensus diagnostic conference. Cox proportional hazards models were used to model time to incident dementia according to severity of hearing loss and were adjusted for age, sex, race, education, diabetes mellitus, smoking, and hypertension.

Setting Baltimore Longitudinal Study of Aging.

Participants Six hundred thirty-nine individuals aged 36 to 90 years.

Main Outcome Measure Incident caces of all-cause dementia and AD until May 31, 2008.

Results During a median follow-up of 11.9 years, 58 cases of incident all-cause dementia were diagnosed, of which 37 cases were AD. The risk of incident all-cause dementia increased log linearly with the severity of baseline hearing loss (1.27 per 10-dB loss; 95% confidence interval, 1.06-1.50). Compared with normal hearing, the hazard ratio (95% confidence interval) for incident all-cause dementia was 1.89 (1.00-3.58) for mild hearing loss, 3.00 (1.43-6.30) for moderate hearing loss, and 4.94 (1.09-22.40) for severe hearing loss. The risk of incident AD also increased with baseline hearing loss (1.20 per 10 dB of hearing loss) but with a wider confidence interval (0.94-1.53).

Conclusions Hearing loss is independently associated with incident all-cause dementia. Whether hearing loss is a markerfor early-stage dementia or is actually a modifiable risk factor for dementia deserves further study.

Author Affiliations: Department of Otolaryngology–Head and Neck Surgery, The Johns Hopkins School of Medicine (Dr Lin), Center on Aging and Health, Johns Hopkins Medical Institutions (Dr Lin), Longitudinal Studies Section, Clinical Research Branch, National Institute on Aging (Drs Metter and Ferrucci), and Departments of Neurology and Medicine, Johns Hopkins Bayview Medical Center (Dr O’Brien), Baltimore, Maryland; and Laboratory of Behavioral Neuroscience, Intramural Research Program, National Institute on Aging, Bethesda, Maryland (Drs Resnick and Zonderman).

– Thanks to NVRC, Fairfax (2/15/11) and KC