When inflammation arises in the body as a result of infection or injury, the immune response also appears to accelerate memory loss in people with Alzheimer’s, according to a recent study published in the journal Neurology. In this study of changes in patients’ cognitive abilities over a span of six months, Alzheimer’s patients who had chronic (ongoing) inflammation as a result of, for instance, obesity or arthritis experienced four times the amount of memory loss as compared with patients without such inflammation. And those with chronic inflammation who also experienced an acute immune response (short-term, such as from an infection) were even worse off: their memory loss accelerated 10 times faster than patients without any inflammation.

“When we started the study, we thought short-lived events would be impor­tant,” says lead author Clive Holmes, a professor of biological psychiatry at the University of Southampton in England. “We hadn’t realized how important chronic inflammation was going to be.”

So how does inflammation, whether from an infection or from chronic dis­ease, damage the brain? The answer lies in the body’s immune response, which launches an attack on invading pathogens, releasing inflaming proteins such as tumor necrosis factor, or TNF. This molecule causes the vagus nerve, which extends from the brain to the abdomen and controls vital functions such as heartbeat, to send an electrical im­pulse to the brain, thereby directing the brain to secrete its own immune messengers.

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