We think 5.3 million Americans have Alzheimer’s disease. But we’re not sure.
The figure is only an estimate because there’s no definitive test that tells doctors and patients Alzheimer’s, a form of dementia characterized by the formation of abnormal proteins in the brain, is what’s causing memory or behavioral changes.
Right now, the diagnosis is often the doctor’s best guess, based on the patient’s symptoms and behavior, and his or her health history. The only way to be sure a person had Alzheimer’s is to study his or her brain after death and look for the telltale changes the disease causes.
Diagnosing Alzheimer’s earlier
Momentum is building, and researchers are working on a multitude of approaches that could lead to earlier diagnosis of Alzheimer’s, says Dr. Heather Snyder, director of medical and scientific operations for the Alzheimer’s Association.
With most diseases, earlier diagnosis means earlier treatment, which means less damage to the body and, hopefully, remission. For Alzheimer’s, researchers hope finding a biomarker ““ a protein, a molecule, a visible change in the brain ““ will lead to developing those treatments. It’s the kind of reverse engineering that’s showing promise in creating targeted treatments for cancer and other diseases.
Searching for abnormal proteins
Researchers identified two abnormal proteins ““ tau and beta-amyloid ““ strongly linked to Alzheimer’s. Several approaches are being studied, from brain scans, blood tests, skin biopsies and even sniff tests. All are still in the research stage and cannot be requested in a doctor’s office. The studies include:
- Neuroimaging
Currently, doctors use MRI scans of the brain to determine if what looks like Alzheimer’s is really caused by an injury to the brain, such as damage done by a stroke, a tumor or a traumatic injury. But in recent years, scientists have developed radioactive “tracers” (think of the barium used in colonoscopies) that “lights up” on PET scans to show the presence of beta-amyloid plaques in the brain. Just the presence of the plaques isn’t enough to diagnose Alzheimer’s; lots of people who don’t have Alzheimer’s or any dementia symptoms have the plaques.
- Molecular imaging
Biological changes start happening in the brain well before Alzheimer’s symptoms start. Scientists have developed “tracers” that attach to beta-amyloid which, in theory, could help better identify how those changes start. - Cerebrospinal fluids proteins
Research suggests tau and beta-amyloid proteins cause changes in cerebrospinal fluid before Alzheimer’s symptoms begin. Doctors now use lumbar punctures, or spinal taps, to study cerebrospinal fluid to diagnose meningitis and other conditions. Currently, there is no consistent way to measure the protein levels. - Proteins in other fluids
If tau and beta-amyloid proteins show up in cerebrospinal fluid, they might be present in blood, urine and other bodily fluids. Researchers are trying to figure that out. - Skin test
A small, preliminary study found elevated levels of beta-amyloid and tau proteins could be identified through skin biopsies in people with Alzheimer’s and Parkinson’s disease. - Sniff test
Two small studies have shown simple scratch-and-sniff tests might be useful in showing brain cells loss and cognitive impairment. If people can’t identify a common odor ““ or if they keep inhaling when smelling something unpleasant because they can’t identify it ““ it could be a sign of damage. - Mild cognitive impairment research
Studies have shown people with mild cognitive impairment (MCI) ““ memory and learning problems significant enough to be noticed by individuals affected and their loved ones, but not significant enough to interfere with the activities of daily living ““ are much more likely to eventually develop Alzheimer’s or other forms of dementia. Remember, not everyone with MCI develops dementia. - Genetic risk factor profiling
Scientists have identified three genes with rare abnormal variants that lead to the development of Alzheimer’s. They’ve also identified several genes that increase the risk of Alzheimer’s, but don’t directly cause it. They’re working on identifying more genes that might play a role in Alzheimer’s and developing a genetic screening tool that can be used to identify people at risk for Alzheimer’s.
