According to a new research conducted by QIMR Berghofer and QUT, there is no strong genetic evidence that hearing loss causes Alzheimer’s disease, despite both conditions sharing a significant number of genetic variants.
The research findings have been published in the journal Alzheimer’s and Dementia: Diagnosis, Assessment, and Disease Monitoring.
For decades the relationship between Alzheimer’s disease and hearing loss has been in the spotlight, but with recent research focusing on risk factors that, if modified during a person’s lifetime, could potentially prevent a person from developing Alzheimer’s disease.
Senior author and researcher in QIMR Berghofer’s Genetic Epidemiology Research Group Associate Professor Michelle Lupton said her team’s study found about a quarter of the genetic variants that influenced hearing loss were also involved in Alzheimer’s disease.
Associate Professor Lupton said, “We did not find any genetic evidence however that one of the conditions caused the other. The lack of genetic evidence sheds doubt on whether the treatment for hearing impairment would change a person’s chances of developing Alzheimer’s disease in the future. Most of the 25 per cent of genetic variants that were common in both conditions were also associated with inflammation and the body’s immune response.”
“This supports the mounting evidence of the importance of inflammation in Alzheimer’s disease. It’s possible that the relationship between these two traits may be due to a common cause that hasn’t been identified as yet. It is important that patients are always treated for their hearing loss to maintain quality of life, but this study also importantly provides new information on Alzheimer’s disease and indicates that treating hearing loss may not prevent the degenerative illness,” Lupton added.
Brittany Mitchell the first author and Ph.D. candidate said it was one of the largest genetic studies of its kind into the relationship between hearing loss and Alzheimer’s disease.
“We examined DNA from more than 250,000 people with self-reported hearing loss and looked for an overlap in the genetic variants of people who had been diagnosed with Alzheimer’s disease,” she said.
“We identified six genes that were associated with both conditions. We then tested for evidence of a causal association between the traits, using several genetic causality methods, but found no significant evidence that one caused the other in either direction,” she added.
Further steps in this research investigated even larger sample sizes. It tested whether specific clinically diagnosed forms of hearing loss or different ages of onset could have a causal role in Alzheimer’s disease or not.
Over 50 million people around the world currently living with Alzheimer’s disease and are the most common form of dementia. Since 2003 no new drugs have been developed to treat Alzheimer’s disease.
About 32 per cent of people aged 55 years and older are affected by hearing loss.