Spotting signs of cognitive decline is especially important, experts say, because drug treatments and prevention strategies are most effective at the earliest stages of dementia.
A study conducted by University of Wisconsin researchers found a link between hearing loss and mild cognitive impairment, which can be a precursor to Alzheimer's disease. The study tracked a group of 783 people enrolled in the Wisconsin Registry for Alzheimer's Prevention, a study group of people with a parental history of Alzheimer's.
Over a four-year period, 9.2 percent of the cohort self-reported being diagnosed with hearing loss. Comparing their initial performance in cognitive and clinical assessments at the start of the study and their performance four years later, those who reported hearing loss were found to be more likely to score poorer on cognitive tests and roughly three times as likely to have mild cognitive impairment, as compared with those who reported normal hearing.
The study is unique in that it examined late middle-aged adults, whereas most studies usually examine older people, said Taylor Fields, a doctoral student in the Neuroscience Training Program at the University of Wisconsin School of Medicine and Public Health.
The hope is that identifying and treating hearing loss is something that a clinician can do quickly and easily in a non-invasive and affordable way. Hearing loss also offers an accessible way to detect signs of cognitive decline early on, Fields added.
The study was among several whose results were discussed Monday at the annual Alzheimer's Association International Comference in London.
Another University of Wisconsin study found a correlation between subtle changes in everyday speech and early mild cognitive impairment. Researchers analyzed two one-minute speech samples, taken two years apart, from 264 study participants, also drawn from the Wisconsin Registry for Alzheimer's Prevention (WRAP). Based on cognitive testing over eight to 10 years, roughly a quarter of the participants were identified as having early mild cognitive impairment, and this subset of participants was found to have declined faster in verbal fluency in the two speech samples. The content of their speech was less specific, with a higher use of pronouns like "she," "it," and "them." Their fluency was also more disrupted, with more hesitations, word repetitions, and filled pauses like "um" and "uh."
In addition, the participants who were identified as having early mild cognitive impairment used less complex syntax and shorter sentences in their speech, and took longer to express the same amount of content as the cognitively healthy group.
This study is "a way of quantifying everyday talking," said Kimberly Mueller, a research associate with the Wisconsin Alzheimer's Institute at University of Wisconsin School of Medicine and Public Health.
By asking participants to describe a simple picture, the study offers a better representation of the problems that people face when communicating as compared to clinical single-word tests, which is how language is typically assessed in this context, Mueller explained.
However, the declines detected in verbal fluency are "extremely subtle" and are essentially "compensation behavior," said Mueller, so family members may not at this point notice changes in everyday speech. Nonetheless, speech analysis of this kind gives a functional measure of verbal skill and can potentially serve as a cheap and accessible tool for clinicians and researchers assessing cognitive function.
Emergency and urgent hospitalizations is another factor associated with accelerated cognitive decline in older people. Bryan James, an epidemiologist with the Rush Alzheimer's Disease Center at Rush University Medical Center, found that non-elective hospitalizations — that is, hospitalizations in emergency or urgent situations — are associated with an approximately 60 percent acceleration in the rate of cognitive decline from before hospitalization. However, elective hospitalizations, such as for scheduled surgery, were not associated with a change in the rate of cognitive decline.
"These findings have important implications for the medical decision making and care of older adults," James said in a statement. "While recognizing that all medical procedures carry some degree of risk, this study implies that planned hospital encounters may not be as dangerous to the cognitive health of older persons as emergency or urgent situations."