November 16, 2009
Colds and other infections may hasten the decline in memory and thinking skills in people with Alzheimer's disease, researchers report. Respiratory and digestive complaints, were all found to raise the risk of accelerated cognitive decline in those with Alzheimer's.
The findings come from a study of nearly 300 older adults with mild to severe Alzheimer's who were living in Britain. Their caregivers were surveyed about the presence of any infections, falls or other traumas, and blood samples were collected every couple of months during the six-month course of the study.
The researchers found that an increase in a substance called tumor necrosis factor-alpha, or TNF-alpha, increased the risk of memory decline in seniors. TNF-alpha levels are increased by colds and other infections as well as traumas and indicate higher levels of inflammation in the body.
Increasingly, researchers believe inflammation is linked to Alzheimer's disease. Inflammation can damage tissues throughout the body, including the brain. It can also damage blood vessels, including those that feed the brain.
During the study, about half of the adults had one or more colds or other respiratory or GI infections or falls that led to increased levels of TNF-alpha. Those who experienced increased levels of the inflammation marker had twice the rate of cognitive decline than those who hadn't experienced such events.
Some of those with Alzheimer's had high levels of TNF-alpha at the start of the study, an indication they may be suffering from chronic inflammation. Those men and women had four times greater cognitive decline than those who had not have elevated TNF levels. Those with persistently high TNF levels who caught a sinus infection or stomach bug declined 10 times faster.
The authors note that illnesses like colds or urinary tract infections that may have no lasting impact in healthy individuals need to be taken much more seriously in seniors with Alzheimer's, since the increase in inflammation may have notable consequences on thinking and memory. The decline, far from being temporary, remains long after the illness has resolved, the researchers note.
The authors conclude that "dampening down systemic TNF-alpha may prove to be beneficial in Alzheimer's disease." Researchers have tried to use nonsteroidal anti-inflammatory drugs like Celebrex and Aleve in the hopes that quelling inflammation may help to stem the mental decline of Alzheimer's. But so far, such medications have not proven effective in fighting the disease.
It is important to keep in mind that although TNF-alpha may be elevated in these individuals, many other factors have also undergone changes. The most convincing part of this study is the association of illnesses with more rapid decline in Alzheimer's patients.
C. Holmes, C. Cunningham, E. Zotova, J. Woolford, C. Dean, S. Kerr, D. Culliford, and V. H. Perry: "Systemic inflammation and disease progression in Alzheimer disease." Neurology, Volume 73: Sept. 8, 2009, pages 768-774.