(Health.com) -- Gradual hearing loss is a common symptom of
aging, but in some people it may also be an early sign of
Alzheimer's disease or other types of dementia, a new study
suggests. The risk of dementia appears to rise as hearing
declines. Older people with mild hearing impairment -- those who
have difficulty following a conversation in a crowded
restaurant, say -- were nearly twice as likely as those with
normal hearing to develop dementia, the study found. Severe
hearing loss nearly quintupled the risk of dementia. It's
unclear why the loss of hearing and mental function might go
hand in hand. Brain abnormalities may contribute independently
to both conditions, but it's also possible that hearing problems
can help bring on dementia, the researchers say. Hearing loss
may lead to social isolation (which itself has been linked to
dementia), for instance, or it may interfere with the brain's
division of labor. "The brain might have to reallocate resources
to help with hearing at the expense of cognition,"