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Contrera KJ, Betz J, Genther DJ, Lin FR. Association of Hearing Impairment and Mortality in the National Health and Nutrition Examination Survey. JAMA Otolaryngol Head Neck Surg. 2015;141(10):944–946. doi:10.1001/jamaoto.2015.1762
Hearing impairment (HI) is common in older adults. Its prevalence doubles with every decade of life, affecting two-thirds of adults older than 70 years.1 Hearing impairment has been shown to be associated with various negative health outcomes. The association of HI and mortality has been studied in select populations.2,3 We investigated the association of HI and all-cause mortality in a nationally representative sample of adults in the United States.
Using combined data from the January 1, 2005, to December 31, 2006, and January 1, 2009, to December 31, 2010, cycles of the National Health and Nutrition Examination Survey (NHANES), we studied 1666 adults 70 years or older who had undergone audiometric testing. The NHANES is an ongoing epidemiologic study designed to assess the health of the US population using representative samples.4 The NHANES protocol was reviewed and approved by the National Center for Health Statistic’s Institutional Review Board and informed written consent was obtained from all participants. Analysis was conducted from March 1 to May 1, 2015.
Severity of HI was defined per the World Health Organization criteria, based on the pure-tone average of hearing thresholds (in decibels) at speech frequencies (0.5-4 kHz) in the ear with better hearing (no HI, <25 dB; mild HI, ≥25 dB but <40 dB; moderate or more severe HI, ≥40 dB).5 Mortality was determined by probabilistic matching between NHANES data and death certificates from the National Death Index through December 31, 2011.6
Baseline characteristics of participants were compared using the χ2 test. The association between HI and mortality was analyzed using Cox proportional hazards regression models sequentially adjusted for demographic characteristics and cardiovascular risk factors known to be epidemiologically associated with HI. All analyses were weighted and conducted using the Stata statistical software program, version 12 (StataCorp LP).
Compared with individuals without HI (n = 527), individuals with HI (n = 1139) were more likely to be older, male, white, former smokers, less educated, and have a history of cardiovascular disease and stroke (Table 1). In the age-adjusted model, moderate or more severe HI was associated with a 54% increased risk of mortality (hazard ratio [HR], 1.54; 95% CI, 1.08-2.18) and mild HI with a 27% increased risk of mortality (HR, 1.27; 95% CI, 0.83-1.95), compared with individuals without HI (Table 2). After further adjustment for demographic characteristics and cardiovascular risk factors, our results suggest that HI may be associated with a 39% (HR, 1.39; 95% CI, 0.97-2.01) and 21% (HR, 1.21; 95% CI, 0.81-1.81) increased risk of mortality in individuals with moderate or more severe HI and mild HI, respectively, compared with individuals without HI. Analysis restricted to individuals 80 years or younger (in whom age could be adjusted for precisely) yielded results also suggestive of a positive association between HI and mortality.
In this nationally representative sample of adults 70 years or older, moderate or more severe HI was significantly associated with a 54% increased risk of mortality after adjustment for age, although this association was attenuated after adjustment for demographics and cardiovascular factors. We observed a dose-response association, with greater HI being associated with a greater risk of mortality. To our knowledge, this report is the first to investigate the association between HI and mortality in a nationally representative US sample.
Our results are generally comparable with those of previous studies.2,3 Potential mechanisms for these findings include causal (or plausibly bidirectional) connections of HI with cognitive, mental, and physical function. A limitation of this study is that the size of our analytic cohort and duration of follow-up may have limited the power to detect significant associations in our fully adjusted models compared with those of previous studies.2,3 In addition, age was treated as a categorical covariate instead of as the time scale in the Cox analysis, which was necessary because NHANES truncates age at 80 years for confidentiality purposes. This parameterization of age may result in residual confounding owing to the inability to precisely adjust for differences in age.
Future studies are required to explore the basis of the association of HI with mortality and to determine whether therapies to rehabilitate hearing can reduce mortality.
Corresponding Author: Kevin J. Contrera, MPH, Center on Aging and Health, Johns Hopkins Medical Institutions, 2024 E Monument St, Ste 2-700, Baltimore, MD 21205 (email@example.com).
Published Online: September 24, 2015. doi:10.1001/jamaoto.2015.1762.
Author Contributions: Mr Contrera had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Contrera, Betz, Lin.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Contrera, Betz.
Critical revision of the manuscript for important intellectual content: Contrera, Genther, Lin.
Statistical analysis: All authors.
Obtained funding: Lin.
Study supervision: Lin.
Conflict of Interest Disclosures: Dr Lin reported being a consultant to Cochlear, serving on the scientific advisory board for Autifony and Pfizer, and being a speaker for Med El and Amplifon.
Funding/Support: This study was supported in part by the Johns Hopkins Institute for Clinical and Translational Research, grants TL1TR001078 and K23DC011279 from the National Institutes of Health, the Eleanor Schwartz Charitable Foundation, and a Triological Society/American College of Surgeons Clinician Scientist Award.
Role of the Funder/Sponsor: The funding sources had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
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