A new study has found that people with hearing loss are at an increased risk of dementia, including Alzheimer’s disease. It also found that as hearing loss worsens, the risk of dementia may also increase.

The study, published in the Archives of Neurology’s February 2011 issue, 639 participants between the ages of 36 to 90 received cognitive and hearing tests between 1990 and 1994. 125 had mild hearing loss, 53 moderate hearing loss, and 6 severe hearing loss

They were then followed through May 31, 2008, for signs of dementia, including Alzheimer’s. During that time, 58 were diagnosed with dementia, 37 of those with Alzheimer’s.

Researchers in the study found that the risk of dementia increased in those with at least a 25 decibel hearing loss. And the more the hearing loss, the greater the risk. For every 10 decibel increase in hearing loss, the risk of dementia increased 20%.

The study suggests that the risk of dementia may be reduced with improved testing and treatment for hearing loss. “But as a scientist I cannot yet say that curing hearing loss will prevent dementia,” Dr. Luigi Ferrucci, the lead author of the study, said. “We have now opened a window on this association. But there is still a lot of work to be done before we can be sure there is actually a causal relationship.”

While researchers that that “Hearing loss may be causally related to dementia, possibly through exhaustion of cognitive reserve, social isolation, environmental deafferentation [elimination of sensory nerve fibres] or a combination of these pathways,” they also admitted that it is also possible that people with dementia may be over-diagnosed with hearing loss, and vice versa. Or that the dementia and hearing loss may share a common underlying cause.