Although loss of smell has been linked to Alzheimer’s disease, my husband had a sense of smell like a dog until the end of his life, and he was diagnosed with younger-onset Alzheimer’s at 59 years old. But now a new study has shown that diagnosing early onset of the disease might be as simple as smelling peanut butter. It sounds like a kid’s science experiment, but the research was recently published in the Journal of the Neurological Sciences, so scientists are taking it seriously.
People with cognitive decline usually begin the diagnosis process with mental status exams, brain scans and a full physical workup. But graduate student Jennifer Stamps, at the University of Florida's McKnight Brain Institute Center for Smell and Taste, who led the research, has found a way to alert family members and physicians which patients will progress from mild cognitive impairment to Alzheimer’s disease.
Under the guidance of Dr. Kenneth Heilman, a distinguished professor of neurology, the research team found that patients with early-stage Alzheimer's disease had more difficulty smelling peanut butter held at short distances from their nose than people without the disease.
The ability to smell is associated with the first cranial nerve—a set of nerves on the brain's surface—called the olfactory nerve. The olfactory nerve is often one of the first things to be affected in cognitive decline, even before memory loss.
For the study, researchers took a tablespoon of peanut butter and a metric ruler, and asked more than 90 people with either mild cognitive impairment, Alzheimer's, other forms of dementia or no neurological problems, to close their eyes and mouth and block one nostril. The researchers then moved a peanut butter container one centimeter at a time up the ruler until the patient could detect the odor. The experiment was repeated again 90 seconds later with the other nostril. The researchers were blinded to whether subjects had already been diagnosed with early stage Alzheimer's.
The study showed that all 18 patients with early-stage Alzheimer's had trouble smelling the peanut butter with their left nostril until it was an average of 10 centimeters closer to their nose than their test with the right nostril. Patients at the clinic who had other forms of non-Alzheimer's dementia did not show this discrepancy in smelling ability, or had a worse right nostril than the left. Of the 24 patients with mild cognitive impairment, 10 had left nostril impairment and 14 did not, which suggests the former group might go on to develop Alzheimer's. The researchers warned that more studies are needed to fully understand the implications.
If you do this experiment and find results similar to the test done with the 18 patients who have early-stage Alzheimer's, don't panic. If you are concerned about cognitive impairment or memory loss in either yourself or a loved one, contact the Alzheimer's Association (http://www.alz.org/index.asp) for information, and make an appointment with your physician.
Jennifer J. Stamps, Linda M. Bartoshuk, Kenneth M. Heilman. "A brief olfactory test for Alzheimer's disease." Journal of the Neurological Sciences, 2013; 333 (1-2): 19 DOI: 10.1016/j.jns.2013.06.033