According to the World Health Organization (WHO), nearly 57 million individuals across the globe have dementia, with nearly 10 million new cases being reported each year.

In most cases, dementia is caused by an interaction between genetic factors and modifiable environmental factors.

Researchers have identified several modifiable risk factors for dementia, including blood pressure levels, cholesterol levels, education levels, social isolation, alcohol intake, and smoking.

Recent research has also identified an association between age-related hearing loss and the risk of dementia.

Furthermore, various studies have found a link between hearing loss and deficits in cognitive function or changes in brain structure, as demonstrated by brain imaging scans.

However, the few studies that have combined cognitive assessments and brain imaging have used small sample sizes.

In summary, these studies examining the link between hearing loss and dementia have evaluated either cognitive function, brain imaging markers, or future dementia risk, but not all of these variables together.

The present study examined whether hearing loss was associated with brain imaging markers of dementia, cognitive decline, and an increased risk of dementia incidence, using data from a single cohort.

The researchers found that an increase in the magnitude of hearing loss was associated with a concomitant decline in performance on the cognitive test and an increase in brain imaging abnormalities.

Deficits in cognitive performance associated with hearing loss were observed in assessments evaluating executive function, which involves higher-order cognitive functions such as planning, attention, and the regulation of other cognitive functions.

Individuals with mild or greater hearing loss were more likely to exhibit a smaller brain volume and a greater decline in executive functioning than those with normal hearing. Even individuals with slight hearing loss were at increased risk of higher levels of white matter abnormalities.

Using data from the second subgroup, the researchers found that individuals with a slight hearing loss had a 71% higher risk of developing dementia in the follow-up period of over 15 years.

The researchers also examined the impact of the presence of at least one copy of the apolipoprotein ε4 (APOE4) allele, a gene variant that increases the risk of Alzheimer’s disease, on the association between hearing loss and dementia risk.

The association between slight hearing loss or worse and dementia risk was much stronger in individuals with APOE4.

In other words, individuals carrying the APOE4 gene variant and having at least slight hearing loss were at greater risk of dementia than those without the APOE4 gene but having slight hearing loss.

Moreover, among individuals with at least slight hearing loss, participants using hearing aids were at lower risk of dementia than those who did not. Notably, this association was stronger among participants carrying the APOE4 gene.

Lastly, the inclusion of hearing loss, along with other risk factors such as age, sex, education, and APOE4 status, in a standard model to predict dementia risk improved its predictive accuracy.

The study’s findings lend support to a potential role of age-related hearing loss in causing dementia. The mechanism underlying this association between hearing loss and dementia risk needs further investigation.

Scientists think that the hearing loss could lead to social isolation, which could, in turn, increase the risk of cognitive decline. Alternatively, impaired hearing could lead to an increased allocation of brain resources to auditory stimuli and leaving fewer resources for memory and executive function.

However, it must be noted 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,” said Etienne.

In addition to hearing loss assessed by the hearing test, the researchers also collected self-reported data on hearing ability from the participants.

Self-reported data was not always consistent with that from the hearing test, with participants often being unaware of the presence of slight or mild hearing loss.

This underscores the need for regular hearing assessments, especially for individuals over 50, and for their inclusion during routine primary care examinations.

Etienne noted:

“The study shows that hearing loss is not merely a symptom that accompanies aging — it may serve as an early marker of vulnerability to cognitive decline. This is especially important because hearing loss is highly prevalent, often underdiagnosed, and modifiable.”

“The finding that adding hearing loss to dementia-prediction models improves risk classification reinforces its potential value as a routine screening target in primary care, geriatrics, and neurology. For public health, these data support the longstanding idea that treating sensory impairment may be a meaningful—and accessible—avenue for dementia prevention,” he added.

The study’s findings also suggest that hearing aids may help reduce the risk of dementia.