June 1, 2007
Inflammation, long linked to heart disease and other ills, may play an important role in Alzheimer's disease as well, a new study suggests. The findings were published in Neurology, the scientific journal of the American Academy of Neurology.
The study, which is part of the large and ongoing 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 proteins that signal inflammation. Those with the highest levels of cytokines in their blood were more than twice as likely to develop Alzheimer's disease than those with the lowest amount of cytokines.
"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."
Having signs of inflammation, however, does not necessarily mean you will develop Alzheimer's. Many of the study participants 28 percent of the women and 30 percent of the men had high levels of cytokines. Most of these individuals did not go on to develop dementia during the course of the study. Still, those with signs of inflammation made up 42 percent of the cases of Alzheimer's disease that were diagnosed.
The study adds to a growing body of scientific evidence that inflammation may play an important role in the onset of Alzheimer's disease. Autopsy studies reveal that the brains of those with Alzheimer's disease contain inflammatory proteins and other substances linked to inflammation. However, it has not been ruled out that inflammation might be a result (rather than a cause) of Alzheimer's or a related, underlying condition. At this point it appears that inflammatory markers (such as cytokine levels) may be useful in assessing Alzheimer's risk.
Other evidence linking inflammation as a causative agent to Alzheimer's has been inconsistent. Some doctors, for example, have been hopeful that providing seniors with inflammation-fighting drugs, such as aspirin and Aleve, may help to protect against Alzheimer's. Although these medications can be effective against heart disease, strokes, and other ills linked to inflammation, studies generally show they do not have benefits against Alzheimer's.
More research is needed to uncover the causes of Alzheimer's and effective treatments that may halt, or prevent, its onset. The Fisher Center for Alzheimer's Research Foundation continues to fund vital research into the underlying causes of Alzheimer's disease. To learn more, visit www.ALZinfo.org.
Z.S. Tan, A.S. Beiser, R.S. Vasan, et al: "Inflammatory Markers and the Risk of Alzheimer Disease: The Framingham Study." Neurology, Volume 68, Number 22, May 29, 2007, page 1902.