Scientists named an unexpected harbinger of Alzheimer's and Parkinson's diseases

Sense of smell is one of the least studied and underestimated senses. It is directly connected to the areas of the brain responsible for emotions and memory: signals from olfactory receptors immediately enter the olfactory bulb located in the forebrain. This is why smells can evoke strong emotional responses - and just as easily disappear during a cold or with age-related changes. However, the loss of ability to sense smells may not just be a temporary inconvenience. Increasingly, scientists view it as one of the earliest signs of neurodegenerative diseases, including Parkinson's and Alzheimer's.

As reported by BAKU.WS, this was announced by The Conversation.

Up to 90% of people with Parkinson's disease report a decrease in sense of smell many years before movement disorders appear. When tremors or stiffness appear, half of the dopamine neurons have already died, and the disease will have progressed to an advanced stage.

Loss of smell could be a valuable biomarker that would allow detection of the disease at the earliest stage. But this symptom is too nonspecific - it can be caused by age-related changes, viral infections, stress, or damage to the mucous membrane.

Nevertheless, new research shows: in some patients, the disease may begin precisely in the olfactory bulb. Areas of the brain vulnerable to viruses, toxins, or pesticides may be the first to malfunction - and then pathological changes spread to areas responsible for movement.

In Alzheimer's disease, early disorders are often associated with damage to the locus coeruleus in the brain stem. This structure is responsible for wakefulness and emotional reactions and is closely connected with the olfactory system. When this interaction weakens, the ability to perceive smells deteriorates - long before memory lapses appear.

Some Parkinson's patients also experience olfactory hallucinations - phantom smells of smoke, tobacco, wood. At the same time, real sharp smells, such as rubber, smoke, or soap, become barely noticeable. Interestingly, they can smell chocolate or coffee normally.

Several years ago, a phenomenon that initially seemed incredible became known: the specific "smell of Parkinson's," described as woody-musky. It was first detected by Scotswoman Joy Milne - twelve years before her husband's diagnosis. Later, scientists confirmed: the chemical composition of sebum in patients does indeed change.

For doctors, olfactory disorders are an important guideline in the complex differential diagnosis between Parkinson's disease and other movement disorders. And for researchers - a chance to study one of the most vulnerable areas of the brain