Loss of smell red flag for 139 conditions caused by inflammation

Not being able to smell is one of the side effects people report from getting Covid. However a new study has said it can be a sign of 139 diseases - meaning people should get it checked out. Researchers found that failures in the sense of hearing comes before other clinical manifestations, opening a new avenue for treatment through olfactory therapy. The study has identified a significant link between loss of smell and inflammation, related to 139 neurological, somatic, and congenital/hereditary diseases.

Conducted at the Charlie Dunlop School of Biological Sciences in collaboration with the Oxford Centre for Humanities Research, the research highlighted an important connection between olfactory loss and inflammation across a staggering number of conditions.

Published in Frontiers in Molecular Neuroscience and led by Professor Emeritus Michael Leon alongside researchers Cynthia Woo and Emily Troscianko, the study explores a little-known but potentially life-changing connection: the role of the sense of smell in maintaining physical and mental health.

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Scientists stated that olfactory dysfunction occurs early in the development of some medical conditions: “Olfactory loss appears long before any other symptoms of Parkinson’s, and similarly, it is an early sign of Alzheimer’s disease, with the olfactory pathway being the first part of the brain to deteriorate in this condition.”

Olfactory loss also precedes depression, major cardiac events, and multiple sclerosis; therefore, olfactory dysfunction seems to be a prodromal symptom of these conditions,” said the researchers.

Dr Stella Maris Cuevas, an otolaryngologist, expert in smell-allergies and former president of the Otolaryngology Association of Buenos Aires City (AOCBA), explained to Infobae: “The sense of smell has been discredited, undervalued, and underestimated for many years compared to other senses like sight and hearing. This wonderful yet complex sense allows us to smell and taste while eating or drinking.”

She added: “The ability to smell, distinguish, perceive, and enjoy various odours always provides us with a range of sensations, emotions, feelings, pleasures, and vigilance. It gives us security in our daily lives and collectively offers well-being and quality of life.”

Anosmia is the total loss of smell; it is the inability to smell. It usually appears suddenly or abruptly due to various causes. Regarding triggers for damage to the olfactory system, there are several possibilities according to the study’s researchers: “One possibility is a common mechanism affecting both the olfactory system and various neurological and somatic targets. Another is that neurological and somatic conditions produce something that degrades the olfactory system.

"A third possibility is that the olfactory system produces something that puts the brain and body at risk for diseases or expressing symptoms of those diseases. A common product of disease is inflammation, and there is a strong relationship between olfactory dysfunction and elevated inflammation.”

This finding could have key implications for mitigating symptoms and possibly even reducing the onset of certain diseases through therapeutic olfactory stimulation.

Specific aromas can enhance memory by up to 226% in older adults. Olfactory therapy proposes a non-invasive approach to improving brain functions. “The data are particularly interesting because we had already discovered that olfactory enrichment can improve memory in older adults by 226 percent,” said Leon. “Now we know that pleasant aromas can reduce inflammation, which might indicate how such aromas can improve brain health.”

A small study conducted in Chile involving 73 adults with mild to moderate COVID-19 without signs of respiratory failure and 27 people without COVID-19 history showed that those with the disease who suffered from loss of smell exhibited behavioural, functional, and structural changes in the brain.

“Despite increasing evidence, specific clinical factors associated with brain alterations remain elusive, presenting challenges for identifying populations at risk for long-term brain and cognitive impairment following SARS-CoV-2 infection,” explained experts in their scientific work.