Association of Subclinical Hearing Loss With Cognitive Performance

Abstract

Importance: Age-related hearing loss (HL) is a common and treatable condition that has been associated with cognitive impairment. The level of hearing at which this association begins has not been studied to date.

Objective: To investigate whether the association between hearing and cognition is present among individuals traditionally classified as having normal hearing.

Design, setting, and participants: Cross-sectional study of 2 US epidemiologic studies (Hispanic Community Health Study [HCHS], 2008-2011, and National Health and Nutrition Examination Study [NHANES], 1999-2000, 2001-2002, and 2011-2012 cycles). The dates of analysis were November 2018 to August 2019. Multivariable generalized additive model (GAM) regression and linear regression were used to assess the association between HL (exposure) and cognition (outcome). Participants included 6451 individuals aged 50 years or older from the general Hispanic population (HCHS [n = 5190]) and the general civilian, noninstitutionalized US population (NHANES [n = 1261]).

Exposures: Audiometric HL (4-frequency pure-tone average).

Main outcomes and measures: Neurocognitive performance measured by the Digit Symbol Substitution Test (DSST) (score range, 0-113), Word Frequency Test (range, 0-49), Spanish-English Verbal Learning Test (SEVLT) 3 trials (range, 5-40), SEVLT recall (range, 0-15), and Six-Item Screener (range, 0-6); higher scores indicated better cognitive performance.

Results: Among 6451 individuals, the mean (SD) age was 59.4 (6.1) years, and 3841 (59.5%) were women. The GAM regression showed a significant inverse association between hearing and cognition across the entire spectrum of hearing after adjusting for demographics and cardiovascular disease. In separate multivariable linear regressions stratified by the classic binary definition of HL, decreased hearing was independently associated with decreased cognition in adults with normal hearing (pure-tone average ≤25 dB) across all cognitive tests in the HCHS. For example in this group, a 10-dB decrease in hearing was associated with a clinically meaningful 1.97-point (95% CI, 1.18-2.75) decrease in score on the DSST. When using a stricter HL cut point (15 dB), an association was also present in NHANES. The associations between hearing and cognition were stronger or equivalent in individuals with normal hearing than among those with HL. For example, there was a 2.28-point (95% CI, 1.56-3.00) combined cohort DSST score decrease per 10-dB decrease among individuals with normal hearing vs a 0.97-point (95% CI, 0.20-1.75) decrease among those with HL, with a significant interaction term between continuous and binary hearing.

Conclusions and relevance: An independent association was observed between cognition and subclinical HL. The association between hearing and cognition may be present earlier in HL than previously understood. Studies investigating whether treating HL can prevent impaired cognition and dementia should consider a lower threshold for defining HL than the current 25-dB threshold.

Figure 1.. Flowchart of Participant Inclusion and Exclusion for Analysis

DSST indicates Digit Symbol Substitution Test; HCHS, Hispanic Community Health Study; and NHANES, National Health and Nutrition Examination Study. ^aIn NHANES, only individuals aged 60 to 69 years had both audiometry and cognitive testing. Therefore, we were restricted to this age range for our analysis.

Figure 2.. Hearing vs Cognitive Performance in 2 US Cross-sectional Studies Assessed With GAM Regression

Linear regression was used for comparison. Multivariable models were adjusted for age, sex, educational level, and cardiovascular disease. The generalized additive model (GAM) regressions show that the association between hearing loss and cognition is not purely linear and that a stronger association between hearing loss and cognition may exist among individuals with normal hearing than those among those with HL. The SE CIs are in orange shading. HCHS indicates Hispanic Community Health Study; NHANES, National Health and Nutrition Examination Study; and SEVLT, Spanish-English Verbal Learning Test. ^aStatistically significant for linear regression and GAM regression, except the multivariable models for the digit symbol substitute test in NHANES; coefficients and 95% CIs are included in Table 2.

Figure 3.. Hearing vs Cognitive Performance in 2 US Cross-sectional Studies, Assessed With Separate Multivariable Linear Regressions Among Participants With Normal Hearing vs Those With Hearing Loss

All models were adjusted for age, sex, educational level, and cardiovascular disease. HCHS indicates Hispanic Community Health Study; NHANES, National Health and Nutrition Examination Study; and SEVLT, Spanish-English Verbal Learning Test. ^aStatistically significant for a hearing stratum; coefficients and 95% CIs are included in Table 2. ^bStatistically significant for a difference between the 2 hearing strata; coefficients and 95% CIs are included in eTable 3 in the Supplement.