A new study published online in the journal Neurology finds a correlation between chronic illness and increased risk of Alzheimer’s disease.
The research suggests that people with a genetic predisposition to Alzheimer’s can experience a significant cognitive decline after they have experienced Alzheimer’s symptoms for many years.
The researchers found that a person’s risk of developing Alzheimer’s was associated with the severity of their illness and the number of years of treatment they had undergone.
The researchers also found that people who had chronic illness were more likely to experience a cognitive decline, suggesting that chronic illness could play a role in the development of Alzheimer in people with the disease.
In the study, researchers looked at data from over 8,000 people with mild cognitive impairment and Alzheimer’s, and the results showed that people whose genetic susceptibility was higher than their normal genetic makeup had a 50% increased risk for developing Alzheimer.
People with Alzheimer’s who experienced more than two years of cognitive decline had a 75% increased likelihood of developing dementia.
The study also found an association between dementia and an increased risk in people who suffered from chronic disease.
For the study to be credible, the researchers had to rule out the possibility that the researchers were simply comparing a person with a mild cognitive disorder and an average person, as the people in the study were of very different genetic backgrounds.
The findings suggest that cognitive decline can be a risk factor for Alzheimer’s in people at increased risk, and could also be a marker of the severity and duration of dementia.
“We found that individuals who had Alzheimer’s were at increased familial risk of dementia, and in people in our study, it was higher among those who had a genetic susceptibility to Alzheimer disease,” said lead author Shari Lippman, a doctoral candidate in the University of Michigan’s Department of Neurology and the University Health Network.
Lippman is now conducting a larger, more comprehensive study to see whether the genetic risk associated with dementia increases as a person ages.
The team also looked at a number of potential confounders, including socioeconomic status, gender, body mass index (BMI), and the severity or frequency of chronic disease, which could have also contributed to the association between cognitive decline and Alzheimer.
“These findings may also apply to individuals who are already diagnosed with Alzheimer disease and who have experienced the onset of cognitive symptoms after years of having symptoms,” Lippmann said.
The results are a step in the right direction, Lippmich said, and may lead to new treatments for Alzheimer patients.
“It may be that the mechanisms that underlie the link between chronic disease and Alzheimer are different in individuals with a gene variant than those without,” she said.
“What this study has shown is that the risk of cognitive impairment may be more pronounced for people who have had the disease, but they are also at increased genetic risk of the disease.”
The researchers said the results were “very encouraging” and that more research is needed to understand how the link could be stronger for those with a higher genetic risk.
“Our study is the first to show that the genetic predisposing factors are associated with cognitive decline in individuals who have been diagnosed with mild to moderate cognitive impairment,” Liddington said.
“The association between the disease and cognitive decline is particularly interesting, because there is a known genetic association between Alzheimer’s and mild cognitive impairments, and these findings also show that these genetic differences can be associated with cognition.”
However, it is also important to note that the relationship between cognitive impairment, dementia and cognitive dysfunction is likely to be different for each individual.
“The findings have implications for the way that people are diagnosed with cognitive impairment in the first place, said study co-author Shari W. Wiese, MD, associate professor of neurology at the University Hospitals Case Medical Center in Cincinnati.”
This study suggests that cognitive impairment is a common component of dementia and may have a similar mechanism of action to that of the risk for Alzheimer, but it also raises the possibility of other potential mechanisms,” Wiesen said.
Wiesen also said that future research is warranted to determine the exact mechanisms involved in the genetic effects on cognition.
The lead author of the study is Shari M. Lippmans, MSc, a professor of psychiatry and neurology in the Department of Neurosciences at the UH Case Medical School and a member of the National Institute of Neurological Disorders and Stroke.
Liddington is now working on a study of a larger sample, with more people, to examine the role of cognitive functioning in dementia and Alzheimer disease.
Lipman and Wieses co-authored the study with Dr. Matthew S. Stiles, M.D., a research associate in the UHR Department of Psychiatry.
Stiles has been studying the neurobiology of Alzheimer and Parkinson’s disease for nearly a decade.
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