Hearing loss, cataracts, and dementia

Back in December, we wrote about research finding that people who had cataract surgery had a 30% lower probability of developing dementia.  I speculated that there might be a relationship between that and a higher incidence of dementia among people with hearing loss.  Recently, other researchers are seeing a similar connection.  In August 2020, we wrote about a Lancet commission report identifying both hearing loss and loss of vision as modifiable risk factors for dementia.  Combined hearing and vision problems may increase the risk of dementia by 50%.  The hope is that aggressively addressing both of these would significantly lower the incidence of dementia.  

Why should such a correlation exist?  One idea is that sensory dysfunction interferes with social connection which is important to resisting dementia.  If you can't hear people or can't see them well you are likely to simply withdraw socially.  And that's deadly.  

But recent research suggests a broader problem.  Failing to control for sensory dysfunction may be skewing statistics about the prevalence of the dementias.  We wrote earlier this week about the Alzheimer's Association Facts and Figures Report.  The report devoted space to how difficult it has been to accurately count people afflicted by different dementias.  

This week's ALZForum had this article on the correlation between sensory dysfunction and dementia.  One thing they noted is that people who don't see or hear well don't do well on cognitive tests, especially tests involving language and memory.  So the apparent correlation may be partly due to over-counting people with dementia simply because they don't test well.