Loss of Smell Signals Early Neurological Disorders

Loss of the sense of smell is a significant health indicator that may reveal early signs of severe neurological and psychiatric disorders, according to recent research.

Studies suggest that olfactory loss can be among the initial symptoms of neurodegenerative diseases such as Parkinson’s disease. Changes in the olfactory bulbs occur long before visible symptoms appear, due to the accumulation of toxic proteins in these bulbs.

Researchers continue to investigate similar mechanisms in Alzheimer’s disease and dementia associated with Lewy bodies.

Prevalence and Impact of Olfactory Disorders

Statistics indicate that up to 22% of individuals experience some form of olfactory disorder, including reduced smell, complete loss, distorted perception of odors, or sensing smells that are not present.

Scientific interest in this area increased notably following the COVID-19 pandemic. The World Health Organization recorded approximately 780 million confirmed cases since December 2019, with around 60% of recovered patients experiencing loss of smell. This has prompted researchers to expand studies on the relationship between the olfactory system and the brain.

Neurological Connections to Smell Dysfunction

Dr. Zara Patil, a specialist in treating smell and taste disorders, stated that changes affecting the central nervous system often manifest as olfactory disturbances.

She explained that researchers have linked these disturbances to about 139 diseases, although the precise mechanisms remain under study. Patients with depression, schizophrenia, and autism spectrum disorder frequently suffer from impaired smell.

Scientists attribute the strong connection between odors, memories, and emotions to the fact that olfactory signals are transmitted directly to the limbic system in the brain, bypassing the thalamus.

The discovery by scientists Linda Buck and Richard Axel of roughly 1,000 genes responsible for encoding olfactory receptors marked a significant milestone in understanding how smell functions. This achievement earned them the Nobel Prize in Physiology or Medicine in 2004.

Potential Treatments for Smell Loss

Regarding treatment, studies indicate that olfactory training involving repeated exposure to scents such as lemon, rose, clove, and eucalyptus may help some patients regain their sense of smell.

A comprehensive meta-analysis published in 2024, encompassing results from 36 studies, reported noticeable improvement in 30 to 50% of participants, especially when olfactory training was combined with sinus irrigation using steroids.

Evidence also suggests that engaging in physical exercise may contribute to enhancing cognitive functions and alleviating symptoms of depression.