Swedish researchers followed 137 patients for nearly a decade who met the criteria for what’s called mild cognitive impairment (MCI). People with MCI can be forgetful. They may also search for words or have trouble reading or solving problems. But these changes are not severe enough to interfere with daily activities, says Hansson, who is an associate professor in the Clinical Memory Research Unit at Lund University in Malmo, Sweden.
“MCI is a symptom and like other symptoms, for example chest pain, it can be caused by many different conditions,” he says.
As many as half of patients with MCI will develop Alzheimer’s disease within five to 10 years; the other 50% are affected by other conditions like depression, stable forms of memory loss, or other types of dementia, Hansson says.
At the start of the study, researchers collected samples of spinal fluid via spinal tap. They tested the samples for two kinds of protein fragments: beta-amyloid and tau.
Beta-amyloid accumulates in the brains of people who have Alzheimer’s disease. It is thought to cause plaques that alter the function of nerve cells.
Tau proteins form tangles that snarl the insides of brain cells.
Most patients were in their early 60s and 70s when the study began.
Why the Test Is Valuable
Seventy-two people went on to be diagnosed with Alzheimer’s disease. Twenty-one developed other kinds of dementia, and 41 never got worse.
Researchers discovered that nine out of 10 people with MCI who also had low levels of beta-amyloid and high levels of tau in their spinal fluid developed Alzheimer’s disease.
In contrast, those who had MCI but normal protein levels had no higher risk of getting Alzheimer’s than people the same age who didn’t have any memory problems.
Looking at the two kinds of protein fragments together was about 90% accurate in predicting future Alzheimer's disease in people with MCI, which means it probably isn’t precise enough to be used as a standalone test to make an exact diagnosis.
But combining a test of spinal fluid with other tests, like certain brain scans, may improve the accuracy of a doctor’s diagnosis, “thus opening a window for diagnosis and treatment at the earliest possible stage,” Hansson says.
“This is a great study, a very interesting study,” says Paul B. Rosenberg, MD, associate professor of psychiatry and behavioral health at Johns Hopkins School of Medicine and Bayview Medical Center.
“We still don’t know what to do with the results,” he says. “If I give you a test that predicts you have a 90% chance of getting Alzheimer’s within 10 years, what good does that do you?”
The challenge, says Rosenberg, will be to decide who gets these kinds of tests, which can be expensive and uncomfortable.