title: Long-term assessment of systemic inflammation and the cumulative incidence of age-related hearing impairment in the epidemiology of hearing loss study.
abstract: BACKGROUND
  Although research has linked systemic inflammation to various diseases of aging, few studies have examined the potential role it may play in the development of age-related hearing impairment.
  
  
  METHODS
  Among 1,073 participants free of hearing impairment (pure-tone average 0.5, 1, 2, 4kHz ≤ 25 dB HL) in the population-based Epidemiology of Hearing Loss Study (1998-2000), serum C-reactive protein, and interleukin-6 were measured at three time points (1988-1990, 1998-2000, and 2009-2010), and tumor necrosis factor-α was measured at one time point (1998-2000), whereas hearing impairment was measured again in 2003-2005 and 2009-2010 to determine the 10-year cumulative incidence.
  
  
  RESULTS
  Inflammatory marker levels from a single time point (1998-2000) were not associated with an increased risk of developing hearing impairment. Associations between long-term serum C-reactive protein levels and incident hearing impairment differed by age (p = .031). Participants less than 60 years with consistently high (>3 mg/L) or increasing levels of serum C-reactive protein over 10 years were nearly two times (hazard ratio: 1.96, 95% confidence interval: 1.19, 3.23) as likely to develop hearing impairment over the subsequent 10-year period, an association not seen in participants more than or equal to 60 years. A statistically significant association (p-trend = .041) was also observed between number of markers in the highest group at baseline and incident hearing impairment in this younger age group.
  
  
  CONCLUSIONS
  Associations between long-term serum C-reactive protein levels and incident hearing impairment were observed in the cohort as a whole, but differed significantly by age group, with statistically significant associations observed in adults less than 60 years, participants moving through the peak risk period for hearing impairment over the course of the study.
authors.affiliation: Department of Population Health Sciences, University of Wisconsin School of Medicine and Public Health, 610 North Walnut Street, Room 1036 WARF, Madison, WI 53726. snash@wisc.edu.
authors.forename: Scott D
authors.initials: SD
authors.lastname: Nash
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Cruickshanks
authors.forename: Weihai
authors.initials: W
authors.lastname: Zhan
authors.forename: Michael Y
authors.initials: MY
authors.lastname: Tsai
authors.forename: Ronald
authors.initials: R
authors.lastname: Klein
authors.forename: Rick
authors.initials: R
authors.lastname: Chappell
authors.forename: F Javier
authors.initials: FJ
authors.lastname: Nieto
authors.forename: Barbara E K
authors.initials: BE
authors.lastname: Klein
authors.forename: Carla R
authors.initials: CR
authors.lastname: Schubert
authors.forename: Dayna S
authors.initials: DS
authors.lastname: Dalton
authors.forename: Theodore S
authors.initials: TS
authors.lastname: Tweed
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002097:C-Reactive Protein / Q000378:metabolism*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D007249:Inflammation / Q000097:blood / Q000150:complications; D015850:Interleukin-6 / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011304:Presbycusis / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology*; D012307:Risk Factors; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000097:blood*
chemical_list: D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha; D002097:C-Reactive Protein
keywords: Epidemiology; Hearing; Hearing loss; Inflammation; Sensory.