No genetic evidence hearing loss causes Alzheimer disease

New QIMR Berghofer and QUT research on Wednesday said that there is no strong genetic evidence that hearing loss causes Alzheimer’s disease, in spite of both conditions sharing a significant number of genetic variants.

The research finding was published in the journal Alzheimer’s and Dementia: Diagnosis, Assessment and Disease Monitoring.

According to the Journal the relationship between hearing loss and Alzheimer’s disease has been in the spotlight for decades, with recent research focusing on risk factors that if modified during a person’s lifetime, could potentially prevent a person developing Alzheimer’s disease.

Some other studies have suggested mild hearing loss doubles a person’s risk of dementia, while people with severe hearing impairment are five times likely to develop dementia.

Senior Author and researcher in QIMR Berghofer’s Genetic Epidemiology Research Group Associate Professor, Michelle Lupton said her team’s study found that a quarter of the genetic variants that influenced hearing loss were also involved in Alzheimer’s disease.

“We did not find any genetic evidence however that one of the conditions caused the other.

“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,’’ Associate Professor Lupton said.

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 yet.

“It is important that patients are always treated for their hearing loss to maintain quality of life, but this study also provides new information on Alzheimer’s disease and indicates that treating hearing loss may not prevent the degenerative illness,’’ Lupton added.

First author and PhD candidate, Brittany Mitchell 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.

Alzheimer’s disease is the most common form of dementia with over 50 million people around the world currently living with the condition.

No new drugs have been developed to treat Alzheimer’s disease since 2003.

Hearing loss affects about 32 per cent of people aged 55 years and older.