A recent study conducted by DZNE and Ludwig-Maximilians-Universität München (LMU) suggests that loss of smell may serve as an early warning sign of Alzheimer’s disease. Researchers found that Alzheimer’s can lead to damage in the brain’s immune cells, known as microglia, which mistakenly attack healthy nerve fibers essential for the sense of smell. As a result, individuals may experience difficulties in detecting odors years prior to receiving a formal Alzheimer’s diagnosis.
The investigation utilized mouse models, human brain tissue from deceased patients, and PET scans of living individuals diagnosed with Alzheimer’s. Findings indicate that the disease triggers abnormal neuron firing, resulting in a shift of the phosphatidylserine molecule from the inside to the outside of neuron membranes. This alteration signals microglia to eliminate the affected nerve fibers connecting the locus coeruleus, a brain region involved in regulating smell, sleep, and blood flow, to the olfactory bulb, which controls the sense of smell.
Dr. Dale Bredesen, a neurologist specializing in Alzheimer’s, emphasized the potential for neurologists to incorporate routine smell sensitivity tests into patient evaluations before cognitive symptoms emerge. Current Alzheimer’s treatments are most effective when administered early, and identifying patients at risk through smell tests could enable more timely interventions.
Bredesen advocates for individuals over 35 with a family history of cognitive conditions to consider asking their healthcare providers for a smell test. However, he cautions that while these tests may indicate potential risks, they are not definitive. Individuals experiencing a decline in smell should seek medical advice rather than dismissing it as benign. The study represents a significant step toward refining early detection methods that could improve patient outcomes in Alzheimer’s disease.