More studies show relationship between hearing loss and dementia
Data from large British, Taiwanese and German scientific studies and a comprehensive report on dementia show that there is a relationship between untreated hearing loss and dementia. One of the studies supports earlier scientific findings that treating hearing loss with hearing aids reduces cognitive decline, and helps to keep the hard of hearing person mentally fit.
English study
An English study among people aged 50 and older using data from the English Longitudinal Study of Aging showed that participants with both self-reported and measured hearing loss were more likely to have a dementia diagnosis than those with normal hearing. The study found that the hazard of developing dementia was 1.4 times higher in individuals who reported moderate hearing and 1.6 times higher in those who reported poor hearing. The authors write that “these findings are consistent with the rationale that correction of hearing loss could help delay the onset of dementia or that hearing loss itself could serve as a risk indicator for cognitive decline”.
Taiwanese study
A Taiwanese study among 4,108 people with an age-related haring loss and a control group of 4,013 without an age-related hearing loss found that compared with the control group, the risk of dementia was significantly higher among those with an age-related hearing loss (1.3 times as high). People with co-morbidities such as rheumatoid arthritis, hypertension, diabetes, stroke etc. had a 3.6-fold increased risk of developing dementia compared with people without comorbidities. The study also found that women with an age-related hearing loss were more likely to develop dementia than men with an age-related hearing loss.
German study
A large study among 154,783 persons, collected from data of the largest health insurer in Germany between 2006 and 2010 containing 14,602 incidents of dementia, showed that people with hearing impairment had a 1.2 to 1.4 times higher risk of dementia compared with people without hearing impairment. There was no increased risk of dementia if the person with a hearing loss had a unilateral hearing loss.
Report: Nine risk factors
Finally, a comprehensive report from The Lancet Commission on Dementia Prevention, Intervention and Care has found nine risk factors which increase the risk of dementia: education to a maximum age of 11-12, midlife hypertension, midlife obesity, late-life depression, diabetes, physical inactivity, smoking, social isolation – and finally hearing loss.
Why this relationship?
Why is there a relationship between hearing loss and dementia? These scientific studies do not provide an answer. There is as yet no scientifically proven causal relationship between hearing loss and cognitive decline and an explanation of which causes which. It is however assumed by many researchers that the reduced audiological input, as a result of a hearing loss, may increase the risk of developing dementia. Hearing loss may also result in increased social isolation, which again might increase the risk of developing dementia. Furthermore, the combination of reduced audiological input and social isolation may be an explanation.
An extensive French study has shown that treating hearing loss with hearing aids reduces cognitive decline and that those who use hearing aids have about the same cognitive level as those with no hearing loss.
About the studies
The English study “Hearing Impairment and Incident Dementia: Findings from the English Longitudinal Study of Ageing” was published in The Journal of the American Geriatrics Society in 2017
The Taiwanese study “Age-related hearing loss and dementia: a 10-year national population based study” was published in European Archives of Oto-Rhino-Laryngology in 2017.
The German study “Hearing Impairment Affects Dementia Incidence. An Analysis Based on Longitudinal Health Claims Data in Germany” was published in the journal PLOS One in 2016.
The report from The Lancet Commission on Dementia Prevention, Intervention and Care "Dementia prevention, intervention, and care" was published in the Lancet in 2017.
Sources:
The Journal of the American Geriatrics Society, European Archives of Oto-Rhino-Laryngology, PLOS One and the Lancet