Unexpected Discovery Sheds New Light on Cognitive Decline in Older Adults
Research has shown that inflammation plays a role in Alzheimer’s disease (AD), but a recent and unexpected discovery by researchers with Massachusetts General Hospital (MGH) and the Harvard Aging Brain Study (HABS) is shedding new light on the relationship between inflammation and AD.
The researchers found that elevated levels of two pro-inflammatory cytokines are associated with slower cognitive decline in older adults, even though the adults in the study had amyloid deposits in the brain—a chief characteristic of AD. Cytokines are proteins secreted by the immune system and are important to cell signaling. High levels of inflammatory cytokines usually lead to health complications.
But in the study, researchers found that older adults with high levels of interleukin-12 (IL-12) and another cytokine, interferon-gamma (IFN-y), were associated with slower cognitive
decline. “However, men and women with elevated levels of amyloid declined more if they had a lower value of IL-12,” says lead author Hyun-Sik Yang, MD, a neurologist at Brigham and Women’s Hospital and a HABS co-investigator.
Dr. Rudolph Tanzi, PhD, co-director of the Henry and Allison McCance Center for Brain Health at MGH, says the study, while surprising, offers important information about the immune system’s role in the earliest stages of AD. That relationship is still not well understood, but this discovery may help doctors identify healthy people who are at risk for AD well before symptoms develop. Such a tool does not yet exist. “We don’t have a ‘checkup from the neck up,’” Dr. Tanzi says.
Understanding how some people with amyloid plaques remain cognitively healthy is a medical mystery. One possible solution, Dr. Tanzi suggets, may be that high levels of the two cytokines mean that the immune system is more “primed” to protect against amyloid-related injury. The next step is to study how the cytokines promote healthy brain aging.
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