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FRIDAY, July 11, 2003 (HealthDayNews) -- Inflammation in the body, measured by blood tests, is linked to cognitive decline in older adults, a team of researchers has found.
The new study, published in the July 8 issue of Neurology, adds weight to the hypothesis that inflammatory mechanisms in the body play a role in several age-related diseases, including Alzheimer's."There has been a lot of [medical] literature suggesting that inflammation may contribute to Alzheimer's disease and other disorders or aging," says study author Dr. Kristen Yaffe, an assistant professor of psychiatry, neurology and epidemiology at the University of California, San Francisco.
What was not known, she says, was which comes first -- the inflammation or the disease. "My idea was, OK, let's look at blood levels of inflammation. Those who start off with higher levels of the blood markers should have more cognitive decline [over time]. And that is indeed what we found," she says.
Yaffe and her co-researchers followed 3,031 black and white men and women, average age 74, who were enrolled in the ongoing Health, Aging and Body Composition Study. The scientists took blood levels of three known markers of inflammation, including interleukin-6 (IL-6), C-reactive protein and tumor necrosis factor. They repeated the tests two years later.
A battery of mental tests was also given to evaluate concentration, memory, language and other measures of cognitive functioning, both at the start and two years later.
After adjusting for age and other factors, they found that those who had the highest levels of inflammation -- whose blood levels of IL-6 and C-reactive protein were in the highest one-third -- had more cognitive decline compared to those whose blood levels of those substances were in the lower third.
If their IL-6 result was high, they were 34 percent more likely to have cognitive decline than those whose scores on the tests were in the lower third. If their C-reactive protein levels were in the top third, they were 41 percent more likely to have cognitive decline than those in the lower third.
Although those who suffered cognitive decline also had higher levels of tumor necrosis factor, the differences weren't statistically significant, Yaffe says.
While the next logical step -- which is already being studied -- is to determine if preventing inflammation with medication makes any difference, Yaffe says it's too soon to recommend taking drugs to ward off age-related cognitive decline.
And the study found no relationship between the use of anti-inflammatories and inflammation levels.
The study "is a very large, well-done study," says Bill Thies, vice president of medical and scientific affairs for the Alzheimer's Association. The finding "fits with the idea that excess inflammatory activities are somehow related to Alzheimer's."
"And it does suggest that some of these inflammatory markers might be useful" to identify those at high risk for developing cognitive problems, Thies adds.
But to date, Thies says, research looking at anti-inflammatory drugs shows more promise as a preventive option, rather than as a treatment.
Adds another expert, Dr. Joseph Quinn, a neurologist at the Portland (Oregon) VA Medical Center, "There are only two other studies that have suggested that inflammatory markers predict future cognition. And this one is different because it includes multiple markers of inflammation and includes large numbers of African-Americans."
"It is a very solid study," Quinn says. But he adds a caveat: "It is also important to note that these results do not mean that people should start taking anti-inflammatory medicines for the prevention of Alzheimer's."
More information
For more information on Alzheimer's disease, see the Alzheimer's Association. Read about how anti-inflammatories may protect against Alzheimer's disease.
