Hearing Loss and Dementia

 

Age-related hearing loss is independently associated both with decreased cognitive function and increased dementia. The association may be coincidental. Both hearing loss and dementia occur more often in the elderly. (Up to 80% of individuals over the age of 85 have hearing loss.)

 

It is hard to determine the nature of the relationship between dementia and hearing loss.  It may be caused by the fact that the effort to hear and understand speech may draw resources that would otherwise be used for higher-order thinking (cognitive reserve). Hearing loss also can create social isolation and loneliness, which are also risk factors for dementia. It is also possible that poor verbal communication caused by hearing loss may affect cognitive test scores. It’s likely that the interaction of all these components contribute to the relationship.

 

A study of 347 people over age 55 with hearing loss but without cognitive impairment or dementia found they had lower scores on tests of memory and executive function. The same study showed that the risk of all-cause dementia was directly related to the severity of baseline hearing loss.[1] Another prospective study of 836/4462 subjects with hearing loss but without dementia showed that 16.3 % developed over 10 years. Only 12.1% of those without hearing loss developed dementia in the same 10-year period.[2]

 

Hearing loss is due to a central auditory process or natural changes due to aging (e.g. presbycusis) appear to result in similar rates of cognitive decline. Currently no study has shown that hearing aids or aural rehabilitation could alter the course of cognitive decline. However, hearing assessment earlier in life may lead to early intervention and treatment to avert later cognitive decline.

 

Hearing loss can be detected through a pure tone audiogram. In general, a hearing threshold of <25dB is normal; 25-40 dB is mild hearing loss; 41-70 dB is moderate hearing loss, and >70dB is severe hearing loss. Multiple studies have shown that the single question, “Do you feel you have hearing loss?” is nearly as accurate a measure of hearing impairment as hearing tests using pure tone audiometry.[3]

 

[1] Lin FR, Ferrucci L, Metter EJ, An Y, et.al., Hearing loss and cognition in the Baltimore Longitudinal Study of Aging, Neuropsychology 2011; 25(6): 763-770.

[2] Gurgel RK, Ward PD, Schwartz S, et.al., Relationship of hearing loss and dementia: A prospective Population-based study, Otol Neurotol 2014; 35(5): 775-781.

[3] Nondahl DM, Cruickshanks KJ, Wiley TL, et al. Accuracy of self-reported hearing loss. Audiology 1998; 37:295-301.