Scientists have traced the roots of dementia back to midlife, a time when hearing loss and changes in speech patterns may signal the onset of cognitive decline.
In research presented Monday at the Alzheimer's Assn.'s annual international conference in London, investigators also reported that for people in their 80s, those who were admitted to a hospital for an urgent or emergency medical problem subsequently suffered more dramatic decline in mental functioning than their peers who checked into a hospital for an elective procedure or avoided the hospital altogether.
Collectively, the new research helps sketch a fuller picture both of who is at risk of cognitive decline and how early those processes probably begin. It suggests that even when a diagnosis of Alzheimer's disease or another form of dementia could be years away, factors detectable when a person is in her 50s and 60s may signal — or even contribute to — the disease process.
It also offers further evidence that certain behaviors, including vibrant intellectual and social engagement, offer some protection from the ravages of cognitive decline as we age.
In a University of Wisconsin study that tracks the cognitive health of more than 1,500 middle-aged adults, researchers selected a subset who had at least one parent with Alzheimer's to investigate changes in speech patterns and what they might portend. All of these participants recorded at least two minute-long verbal descriptions of a picture, separated by at least two years.
The researchers focused on 64 participants whose test results over eight to 10 years led to a diagnosis of mild cognitive impairment, or MCI, a condition that often progresses into Alzheimer's disease. Their average age was 60 years old.
The speech patterns of these participants differed in subtle but measurable ways from those of study subjects who were not diagnosed with MCI, the researchers found. They tended to use shorter, simpler sentences, and their delivery was more halting.
The researchers also compared changes in verbal samples taken two years apart. They observed that in participants who had established mild cognitive impairment, the flow of descriptive language changed more dramatically over two years — becoming even less fluid — than it did in participants with no such diagnosis. Those with MCI grew more likely to pause, repeat words, or insert pauses like "um" and "ah" into their everyday speech.
The researchers were surprised to observe that, in their first everyday language sample, people with MCI actually had used more descriptive and uncommon words than their counterparts who were cognitively healthy. But over two years' time, the participants with MCI showed a much steeper decline in the "semantic" complexity of their speech. They increasingly used simpler words as they described objects, people and places in their pictures. They used more pronouns — he, she, it and they — and fewer nouns that would have been more specific.
The study's lead author, Kimberly Mueller of the Wisconsin Alzheimer's Institute, said speech analysis "may be a valuable cognitive marker" for early detection of cognitive slide. The next step, she said, would be to see how easy-to-detect changes in speech patterns align with some of the hallmark brain changes that come with Alzheimer's.
The role of hearing in predicting dementia also emerged as an early marker for cognitive decline — but one more amenable to modern fixes.
In a study that looked at 783 fiftysomethings participating in the University of Wisconsin study, researchers found that those reporting a diagnosis of hearing loss performed worse on a welter of tests of cognitive skills. In addition, when they were examined not more than four years later, those with hearing loss were more than three times likelier than their peers with normal hearing to be diagnosed with mild cognitive impairment.
Experts have long surmised that hearing loss may deepen the isolation of a sufferer, limiting social and intellectual engagement and accelerating an individual's cognitive decline.
But aside from being a telling detail, it's not yet clear what the relationship between hearing loss and dementia is. Long-standing research has shown, for instance, that one of Alzheimer's earliest warning signs is a lost sense of smell. But few experts believe that an impaired olfactory sense accelerates Alzheimer's; rather, they suspect that the brain's olfactory bulb is one of the first regions affected by the proteins that clump in the brain.
Hearing loss is, however, a problem with a ready fix — the hearing aid. The study authors suggest that more widespread use of such corrective technologies might make a difference in Alzheimer's rates.
"Identification and treatment of hearing loss might be a viable approach to forestall the public health crisis posed by Alzheimer's disease," wrote the authors, all from the University of Wisconsin's School of Medicine and Public Health.
The National Institutes of Health estimates that about 37.5 million Americans have hearing loss, and 28.8 million of them could benefit from hearing aids. But even among those most likely to use them — people 70 and above with hearing loss — only 30% have ever used one.
For patients in their 80s, an emergency trip to the hospital may be more difficult to avoid than deafness. But a third study presented Monday in London found that elderly adults who had a hospital stay for an urgent medical need were more likely to suffer a subsequent cognitive decline than were those not admitted to any hospital.
And compared to their peers who had an elective hospital stay, the cognitive decline of emergency patients was almost twice as fast after they left the hospital. That study was conducted by researchers at the Rush University Medical Center's Memory and Aging Project, which has tracked the cognitive health of older Chicago residents since 1997.
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