The paper was recently published in the Journal of Alzheimer's Disease.
This number is predicted to rise to almost 14 million by 2050.
The search continues for the exact causes of Alzheimer's, but a sticky protein called beta-amyloid is believed to play a role in the disease.
Beta-amyloid can clump together and form "plaques" in the brain. These plaques will interfere with brain cell communication, which can lead to memory loss, behavioral changes, and many other symptoms characteristic of Alzheimer's disease.
In a study published last year, Dr. McGeer and colleagues revealed that a beta-amyloid peptide — known as amyloid-beta 42 (Abeta 42) — is present in saliva, as well as the brain, and that levels of this peptide are higher in adults who are at greater risk of Alzheimer's.
Based on those results, the team suggests that a saliva test could be used to predict the risk of Alzheimer's disease years before symptoms arise.
"What we've learned through our research," reports Dr. McGeer, "is that people who are at risk of developing Alzheimer's exhibit the same elevated Abeta 42 levels as people who already have it; moreover, they exhibit those elevated levels throughout their lifetime so, theoretically, they could get tested anytime."
A 'true breakthrough'?
In their paper, the researchers claim that ibuprofen — a widely used nonsteroidal anti-inflammatory drug (NSAID) — could prevent the development of Alzheimer's in people with high levels of Abeta 42.
Dr. McGeer and team point to previous research that they conducted, in which they suggested that Abeta 42 triggers an inflammatory response.
This response could be reduced by ibuprofen and other NSAIDs, say the researchers, which could stop Alzheimer's in its tracks.
The team says that identifying the risk of Alzheimer's through a saliva test would offer people the opportunity to prevent Alzheimer's development through a daily dose of ibuprofen.
"Knowing that the prevalence of clinical Alzheimer's disease commences at age 65," explains Dr. McGeer, "we recommend that people get tested 10 years before, at age 55, when the onset of Alzheimer's would typically begin."
"If they exhibit elevated Abeta 42 levels then, that is the time to begin taking daily ibuprofen to ward off the disease."
Dr. Patrick McGeer
He hails the saliva test as a "true breakthrough" because it "points in a direction where [Alzheimer's disease] can eventually be eliminated." However, Dr. McGeer's claims have been met with some criticism.
Daily ibuprofen recommendation 'premature'
Dr. Doug Brown, chief policy and research officer at the Alzheimer's Society in the United Kingdom, believes that it is far too soon to be recommending daily ibuprofen for Alzheimer's prevention.
"Population studies," he says, "which gather large amounts of information from medical records from thousands of people, have thrown up an idea that taking ibuprofen and other over-the-counter anti-inflammatories might be linked to a lower risk of dementia."
"But results of clinical trials with these drugs have been disappointing so far."
"The researchers' suggestion in this paper that taking a daily anti-inflammatory drug as soon as a positive result for dementia risk is shown by a saliva test is premature," adds Dr. Brown, "based on the evidence at the moment."
He also notes the risks of long-term NSAID use, including intestinal bleeding and stomach ulcers. NSAIDs may also interact with other medications, such as warfarin, and produce harmful effects.
"We always recommend talking to your doctor before changing your medication," Dr. Brown says.