Hearing Loss May Hasten Cognitive Decline More Than We Think
Hearing loss can seem just like an inevitable part of ageing for some. However, the evidence is more serious. Untreated hearing loss is now recognised as one of the most significant modifiable risk factors for cognitive decline [1]. A new study found that even mild hearing loss in midlife may accelerate brain aging, impact cognitive function, and significantly increase dementia risk [2].
Long-term large-scale cohort sample
Researchers at Boston University and other American institutions analysed data from participants enrolled in the Framingham Heart Study – a large-scale community study that tracks the risk of cardiovascular and other diseases within families [3]. The 2,178 participants were assigned to two partially overlapping groups and followed for 15 years. One group, with a mean age of 58 years, was used to assess the link between hearing loss and brain imaging markers and cognitive performance. The other group, with an average age of 68 years, was used to examine the association between hearing loss and dementia incidence.
Extensive Assessments
All participants underwent a hearing assessment during the first (baseline) visit, and were classified as having normal, slight, mild, or moderate-to-severe hearing loss, accordingly. The magnetic resonance imaging (MRI) scans and cognitive tests for the first subgroup were conducted during the subsequent visits at 4 or 8 years after the initial visit. Genetic testing was also completed to see whether participants carried the apolipoprotein ε4 (APOE-e4) gene variant, which increases the chance of developing Alzheimer’s disease.
Consistent evidence for the importance of good hearing
The research team found that hearing loss was associated with an accelerated decline in higher-order executive cognitive functions, such as planning and attention. Individuals with mild or greater hearing loss were more likely to exhibit signs of brain ageing, such as smaller brain volume; as well as a larger volume of white matter abnormalities – a sign of blood vessel disease that increases the risk of developing Alzheimer’s Disease.
Moreover, individuals with slight hearing loss had a 71% higher risk of developing dementia over the 15 years. This risk was nearly tripled for those who inherited the APOE-e4 gene. To cement the strong findings, the inclusion of hearing loss in a statistical model alongside other risk factors such as age, sex, education and APOE-e4 status, significantly increased the accuracy of predicting dementia risk.
Hearing aids may mitigate risk
The good news was that individuals who wore hearing aids to correct their hearing loss, significantly reduced their risk of developing dementia. This effect was particularly pronounced for APOE-e4 carriers. The results underscore the importance of getting hearing tests even in midlife; and if even slight hearing impairments are detected, a hearing aid may be a wise investment for long-term brain health. Scientists think that hearing loss could lead to social isolation and depression, which are both well recognized risk factors for Alzheimer’s disease [4]. Alternatively, straining to hear things can take a lot of mental effort, and may pull resources away from other thinking tasks. However, it is important to note that the study was observational and hence does not establish a causal role for hearing loss in dementia incidence. Hearing loss may contribute to dementia risk, but it could also reflect early neurodegenerative changes. Or poor blood flow or circulation risk factors (e.g., high blood pressure and high cholesterol) could be responsible for both hearing loss and dementia. Either way, getting your hearing checked regularly can only be a good thing.
[1] https://www.thelancet.com/infographics-do/dementia-risk
[2] https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2841000