When doctors treating Alzheimer’s patients took a closer look at who seemed to be succumbing to the disease, they uncovered a tantalizing clue: those who were already taking anti-inflammatory drugs for arthritis or heart disease tended to develop the disorder later than those who weren’t. Perhaps the immune system mistakenly saw the characteristic plaques and tangles that build up in the brains of Alzheimer’s patients as damaged tissue that needed to be cleared out. If so, the ensuing inflammatory reaction was doing more harm than good. Blocking it with anti-inflammatories might limit, or at least delay, any damage to cognitive functions.

The most likely culprits this time around are the glial cells, whose job is to nourish and communicate with the neurons. Researchers have discovered that glial cells can also act a lot like the mast cells of the skin, producing inflammatory cytokines that call additional immune cells into action. “The glial cells are trying to return the brain to a normal state,” explains Linda Van Eldik, a neurobiologist at Northwestern University Feinberg School of Medicine in Chicago. “But for some reason, in neurodegenerative diseases like Alzheimer’s, the process seems to be out of control. You get chronic glial activation, which results in an inflammatory state.”

It appears that some people are more sensitive to plaques and tangles than others. Perhaps they have a genetic predisposition. Or perhaps a long-running bacterial infection, like gum disease, keeps the internal fires burning and tips the balance toward chronic inflammation.

Preliminary research suggests that low-dose aspirin and fish-oil capsules — both of which are known to reduce inflammatory cytokines — seem to reduce a person’s risk of Alzheimer’s disease. Unfortunately, most of these preventive measures need to be started well before any neurological problems develop. “What we’ve learned with dementia is that it’s very hard to improve people who already have it,” says Dr. Ernst Schaefer, a professor of medicine and nutrition at Tuft’s Friedman School of Nutrition in Boston. “But it may be possible to stabilize people and to prevent disease.”