Drugs used for arthritis could also be used to treat Alzheimer's disease, say experts.
Doctors have found that inflammation linked to the painful joint condition plays an important role in triggering the deadly brain disease.
The inflammation boosts production of toxic cells in the brain called plaques.
"With this link, we have a new path to potentially identifying and attacking this horrible disease," the Daily Express quoted the leader of the research, Dr Douglas Golenbock, as saying.
One expert said the evidence could lead to the "Holy Grail" in the study of the disease.
"As current treatments merely stabilise the condition, finding ways to stop the physical causes building up in the first place is the Holy Grail for researcher," said Jess Smith, of the Alzheimer's Society.
"Studying how the brain protects itself from injury is helping us reach that goal. The next step is to explore how drugs for inflammation and arthritis could be used to combat the condition. One in three people over 65 will develop dementia. Identifying already existing drugs which could be used to treat dementia is vital to get new treatments on the shelf in a fraction of the time it takes to develop drugs from scratch," Smith added.
The study found that an immune process in the body sparks the production of a protein called interleukin-1 beta (IL-1B).
This protein is involved in the body's defence against infection and has also been pinpointed as a drug target for rheumatoid arthritis - which occurs when the immune system attacks joints, causing pain and inflammation.
The study, published in the journal Nature, points to the possibility that drugs that disrupt the production of IL-1B, such as those for rheumatoid arthritis, may also benefit Alzheimer's patients.
Previously, brain inflammation in Alzheimer's sufferers was thought to be a side effect. But increasing scientific evidence suggests that it might be a primary cause, raising the possibility of fighting Alzheimer's with common anti-inflammatories such as aspirin and ibuprofen.
The latest study examined the destructive amyloid beta plaques, which are a hallmark of Alzheimer's, clumping together in the brain and destroying it, leading to memory loss and confusion.
"The findings are still at an early stage but research into inflammation in Alzheimer's is an important area for the future," said Dr Simon Ridley, of Alzheimer's Research UK.