Relationship of hearing loss and dementia: a prospective, population-based study

Abstract

Objective: To determine whether baseline hearing loss increases cognitive decline and risk for all-cause dementia in a population of elderly individuals.

Study design: Longitudinal cohort study.

Setting: Community-based, outpatient.

Patients: Men and women aged 65 years or older without dementia at baseline.

Intervention(s): All subjects completed the Modified Mini-Mental Status Exam (3MS-R) at baseline and over 3 triennial follow-up visits. Hearing loss (HL) at baseline was based on observation of hearing difficulties during testing or interview. Incident dementia was determined by clinical assessment and expert consensus.

Main outcome measure(s): Dementia and 3MS-R score.

Results: At baseline, 4,463 subjects were without dementia, 836 of whom had HL. Of those with HL, 16.3% developed dementia, compared with 12.1% of those without HL (p < 0.001). Mean time to dementia was 10.3 years in the HL group versus 11.9 years for non-HL (log rank test p < 0.001). In Cox regression analyses controlling for sex, presence of APOE- [Latin Small Letter Open E]4 allele, education, and baseline age, and cardiovascular risk factors, HL was an independent predictor of developing dementia (hazard ratio = 1.27, p = 0.026 [95% CI, 1.03-1.56]). Linear mixed models controlling for similar covariates showed HL was associated with faster decline on the 3MS-R, at a rate of 0.26 points/year worse than those without HL.

Conclusion: Elderly individuals with HL have an increased rate of developing dementia and more rapid decline on 3MS-R scores than their nonhearing impaired counterparts. These findings suggest that hearing impairment may be a marker for cognitive dysfunction in adults age 65 years and older.

Figure 1

A hazard plot for all-cause dementia based on hearing loss controlled for the four main covariables: gender, presence of APOE-ε4 allele, education, and baseline age. The cumulative hazard is shown on the y-axis with years since baseline assessment on the x-axis. The broken line represents those subjects without baseline hearing loss (HL) and the solid line represents those with HL. Cum Hazard = cumulative hazard, HL = hearing loss

Figure 2

This Kaplan-Meier plot shows time to dementia in years of follow up (“cumulative survival”) based on baseline hearing status. Those with hearing loss depicted on the lower line had a higher rate of incident dementia (p<0.001).

Figure 3

This graph shows a linear mixed effects model controlling for age, gender, education and presence of APOE-ε4 allele. At baseline, mean 3MS-R for those with hearing loss is 1.27 points lower than those without hearing loss (fixed effect of hearing loss [HL]). Over time, those who had hearing loss at baseline decline 54% faster, an average of 0.71 points/year, as opposed to 0.46 points/year among those without (time effect of HL). The parallel lines above the broken and solid line represent 95% confidence interval bars, which are non-overlapping. 3MS-R = Modified Mini-Mental State (3MS-R) examination.