People whose blood shows signs of inflammation are more likely to later develop Alzheimer's disease than people with no signs of inflammation, according to a new study.

The study, which is part of the larger Framingham Heart Study, involved 691 healthy people with an average age of 79. Blood tests determined whether the participants had signs of inflammation. Then the participants were followed for an average of seven years. During that time, 44 of the participants developed Alzheimer's disease.

The participants' blood was tested for levels of cytokines, which are protein messengers that trigger inflammation. Those with the highest amount of cytokines in their blood were more than twice as likely to develop Alzheimer's disease as those with the lowest amount of cytokines. A total of 28 percent of the women and 30 percent of the men had high levels of cytokines, yet they made up 42 percent of the cases of Alzheimer's disease.

"These results provide further evidence that inflammation plays a role in the development of Alzheimer's disease," said study author Zaldy Tan, MD, MPH, of Harvard Medical School in Boston. "The production of these cytokines may be a marker of future risk of Alzheimer's disease."

The study was supported by grants from the National Institute of Neurological Disorders and Stroke, the National Institute on Aging, the Boston University Alzheimer's Disease Center, and the National Heart, Lung and Blood Institute's Framingham Heart Study.

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