title: Hearing loss and incident dementia.
abstract: OBJECTIVE
  To determine whether hearing loss is associated with incident all-cause dementia and Alzheimer disease (AD).
  
  
  METHODS
  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.
  
  
  METHODS
  Baltimore Longitudinal Study of Aging.
  
  
  METHODS
  Six hundred thirty-nine individuals aged 36 to 90 years.
  
  
  METHODS
  Incident cases 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 marker for early-stage dementia or is actually a modifiable risk factor for dementia deserves further study.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins School of Medicine, JHOC 6120, 601 N Caroline St, Baltimore, MD 21287, USA. flin1@jhmi.edu
authors.forename: Frank R
authors.initials: FR
authors.lastname: Lin
authors.forename: E Jeffrey
authors.initials: EJ
authors.lastname: Metter
authors.forename: Richard J
authors.initials: RJ
authors.lastname: O'Brien
authors.forename: Susan M
authors.initials: SM
authors.lastname: Resnick
authors.forename: Alan B
authors.initials: AB
authors.lastname: Zonderman
authors.forename: Luigi
authors.initials: L
authors.lastname: Ferrucci
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000523:psychology*; D001299:Audiometry; D015142:Baltimore / Q000453:epidemiology; D016001:Confidence Intervals; D003704:Dementia / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology* / Q000523:psychology; D005260:Female; D005500:Follow-Up Studies; D034381:Hearing Loss / Q000150:complications* / Q000453:epidemiology* / Q000523:psychology; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index