When olfaction rhymes with cognition

In the Graham laboratory we work on understanding the link between the sense of smell and our mental processes, including problem-solving, learning, and memory. Our goal is to develop, validate and promote the use of olfactory tests and olfactory therapy in order to delay cognitive decline and attenuate neuropsychiatric symptoms such as depression, aggression, and anxiety.

Dementia in numbers

• More than 55 million people worldwide are living with dementia.
• Roughly 24% of seniors have Mild Cognitive Impairment.
• The worldwide economic burden of dementia is more than $1.3 trillion.

This has a huge impact on the individual, on families and on society. Indeed, many countries cannot afford dementia care. Even in Canada, it is difficult to get appropriate care. We desperately need cost-effective, efficient strategies that delay the onset of dementia.

Olfactory loss in neurodegenerative diseases

Loss of olfactory function is one of the earliest symptoms in conditions such as Alzheimer’s disease, Mild Cognitive Impairment, Parkinson disease, and stroke — affecting approximately 90% of cases. This loss is also linked to a higher risk of developing dementia and increased neuropsychiatric symptoms, including depression, aggression, and anxiety.

Risks of olfactory dysfunction

• You can’t smell gas, smoke, or rotten food.
• Appetite changes can lead to weight loss.
• Increased risk of depression.
• Higher probability of developing dementia.
• Stress on the family and reduced quality of life.
• Individuals require care and monitoring, which can mean hospitalization, a care home, or constant care — and often means the family becomes caregivers.
• Significant economic burden.

What is olfactory therapy?

Olfactory therapy involves smelling four odors twice a day. Several companies now sell olfactory therapy kits. The odors act as a memory trigger and thus help us to access our memories. Because of this close relation to memory, olfactory therapy has been shown to improve not only olfaction, but also to enhance cognitive functions, reduce symptoms of depression, and improve quality of life.

The standard routine is rose, clove, eucalyptus, and lemon, sniffing each for 20 seconds — over a period of at least 4 months, at a frequency of twice a day. A kit costs approximately $30 per person.

Mild Cognitive Impairment, Alzheimer’s and Parkinson disease all demonstrate early olfactory loss. Using this user-friendly and cost-effective therapy could help to delay and/or reduce the symptoms of these neurodegenerative diseases that cost more than a trillion dollars in health care expenses worldwide each year.

How do we treat olfactory loss?

Standard olfactory tests and therapy exist, but they are not presently part of our public health care in Canada and thus are not freely available to the general population. A public Smell and Taste clinic would make olfactory testing available to the general population and offer olfactory therapy.

Olfactory deficits can happen for several reasons, including car accidents, traumatic brain injuries, and/or the progression of diseases. Situations where olfactory deficits can occur include:

• Prolonged exposure to chemicals
• Infectious disease (influenza, COVID-19)
• Head trauma
• Mild Cognitive Impairment
• Alzheimer’s and Parkinson disease
• Aging

An innovative approach

An innovative approach taken by the laboratory of Professor Rona Graham is to identify the odors related to cognitive loss in different diseases. An olfactory signature has been identified in different diseases, and the next step will be to validate these signatures in a larger population. In the future, we hope to develop and validate olfactory kits that will highlight disease-specific olfactory losses, allowing for early and affordable detection.

Spreading the knowledge

• Synthesising and spreading olfactory knowledge to clinicians, specialists, medical students, and the public.
• Train clinical residents to detect and treat loss of olfaction — fellowships available.
• Develop a web-based telehealth platform that explains how to do olfactory testing and tests for cognitive function, what the results mean, and — if the results suggest deficits — how to do olfactory therapy.
• Present at neurology and medical conferences, physician seminars, public events, and podcasts, and publish in scientific journals, magazines, and public forums.

Develop health care policy

• Patients with and without neurodegenerative diseases should be tested for olfactory dysfunction.
• Canadians in the general population who have issues with their sense of smell should be tested for olfactory function and referred to specialists.
• Develop disease-specific, efficient, and affordable olfactory tests.
• Elementary school children should be tested for olfactory function, as they are for vision and hearing.

Establish smell and taste clinics

• The general public and patients should be offered olfactory therapy.
• Olfactory therapy should be available to all Canadians experiencing smell loss, as a therapeutic strategy that may delay future health complications.
• Implement an affordable and efficient smell-based sensory programme for individuals with dementia who cannot do the routine olfactory therapy protocol themselves.
• Develop a Smell and Taste Clinic in Canada that specialises in olfactory testing and therapy.

The potential

Dementia care costs in Canada are $40.1 billion annually ($67,200 per person per year). If just ~20% of the people with Mild Cognitive Impairment who will go on to get Alzheimer’s disease are delayed — even by only one year — that would save roughly $700 million per year.

In Germany, olfactory testing — and therapy when needed — is mandated and integrated into official Ear, Nose, and Throat (ENT) medical guidelines. In Dresden, the Interdisciplinary Clinic for Smell & Taste brings together healthcare professionals to provide testing, treatment, and research on olfactory disorders under one roof.

Olfactory function plays a vital role in overall health. Investing in olfactory therapy may significantly reduce the billions of taxpayer dollars currently spent on dementia care.