Freshly baked cherry pie. Roast turkey. Warm mulled cider. Do the thoughts of these smells have you salivating? Old Spice men’s aftershave lotion (my Dad’s favorite). Skunk spray. Lilacs in bloom. Ammonia. Sweaty clothes. What memories do these odorants arouse?
Our incredible sense of smell serves many functions. It is a “portal” to our emotions. It is one of the drivers of what we eat and drink. Our ability to smell alerts us to possible dangers, and is critical to our good health and quality of life.
How Our Sense of Smell Works
The average human being, it is said, can recognize up to 10,000 separate odors. Our human olfactory (smell) system has approximately four hundred different receptors. These enable us to detect and identify thousands of odorants. Odorants are microscopic molecules released by substances around us that become airborne. When we breathe or sniff the air, these odorants are drawn into our nose, entering a complex system of nasal passages.
Lining a portion of these nasal passages is the olfactory epithelium, a thin sheet of mucus-coated sensory tissue located high inside the nose. The odorant molecules we breathe in settle into the mucus, making contact with and stimulating the specialized olfactory sensory cells, called sensory neurons. Each of these forty million different olfactory neurons has one odor receptor. These nerve cells connect directly to the brain.
Each nerve cell has thin threadlike projections called olfactory cilia which float in the mucus. Olfactory cilia contain the molecular wherewithal for detecting and starting the process to recognize the odors, and for generating an electrical signal to be sent to the brain.
Electrical signals are sent to the brain along a thin nerve fiber known as an axon. Axons from the millions of olfactory receptor cells bundle together to form the olfactory nerve. Olfactory receptor cells send electrical messages via the olfactory nerve to the olfactory bulb.
Odor information eventually travels to the limbic system, the part of the brain involved in emotion and memory. Other odor information goes to the olfactory cortex where thought processes take place. Cross-connections between the limbic system and the cortex may be essential in forming our emotionally-laden and lifelong olfactory memories. The odor memories we make as children last many years.
Odorants reach the olfactory sensory cells in two ways: 1) by inhaling through the nose; 2) by chewing our food aromas are released through the channel that connects the roof of the throat to the nose. This is one reason why, when we are congested due to a sinus infection, flu, or a head cold, this channel is blocked, affecting our ability to smell and taste our food.
Our sense of smell is also influenced by what is called the common chemical sense. This sense involves thousands of nerve endings, especially on the moist surfaces of our eyes, nose, mouth and throat. These nerve endings help us sense irritating substances – like the tear-inducing power of an onion, or the coolness of menthol.
Types of Smell Disorders
According to the National Institutes of Health, Senior Health, there are several types of smell disorders depending on how the sense of smell is affected.
- Hyposmia occurs when a person’s ability to detect certain odors is reduced.
- Anosmia is the complete inability to detect odors.
- Parosmia is a change in the normal perception of odors, such as when the smell of something familiar is distorted, or when something that normally smells pleasant now smells foul.
- Phantosmia is the sensation of an odor that isn’t there.
The Importance of Smell
Our sense of smell can serve as a first warning signal, alerting us to spoiled food, the odor of a natural gas leak or dangerous fumes, the smoke of a fire. When smell is impaired, it can also lead to a change of eating habits. Some people may eat too little and lose weight, or eat too much and gain weight. In severe cases, loss of smell can lead to depression.
Assessments for Loss of Smell
Serious smell loss can be caused by nasal obstruction that requires corrective surgery or by chronic viral infections with swelling that require special medications. Otolaryngologists are physicians who specialize in diseases of the ear, nose, and throat, including problems affecting taste and smell. An accurate assessment of smell loss includes:
- Physical examination of the ears, nose, and throat.
- Personal history including exposure to toxic chemicals or trauma.
- Smell tests.
- Discussion of treatment options, such as surgery, antibiotics, or steroids.
Alzheimer’s, Dementia and Olfactory Testing
An impaired sense of smell is normal as we age. Older people become less adept at identifying smells. Researchers estimate that more than one-third of adults over age seventy have olfactory deficits.
Losing our sense of smell could be a sign of brain damage. The sense of smell is often the first sense to go in cognitive decline, even before memory loss. It’s not the nose’s sensitivity that diminishes, but the brain’s capability of identifying what the odors are. However, not all individuals with smell loss will develop a brain-related disorder.
Olfactory testing is gaining attention as researchers are discovering that changes in odor identification and loss of ability to smell may be an early biomarker in identifying Alzheimer’s, Parkinson’s, and other neurodegenerative disorders. Multiple studies have demonstrated a high correlation between Alzheimer’s disease and the presence and build up of beta amyloid protein and tau pathology in the areas of the brain that help us detect and perceive odors.
In one study, researchers at the University of Florida asked over ninety participants to smell a spoonful of peanut butter at a short distance from their nose. Participants included persons with a confirmed early stage Alzheimer’s diagnosis, persons with other forms of dementia, and those who had no cognitive or neurological problems. Only those with a confirmed diagnosis of early stage Alzheimer’s had trouble smelling the peanut butter, with their left nostril. The difference in smell between left and right nostril is unique to the disease. Currently, a smell test is not used as a diagnostic tool, but only to confirm an Alzheimer’s diagnosis. The theory is that, as dementia begins and progresses, the parts of the brain, particularly on the left side, that distinguish odors start to deteriorate. The brain is less capable of identifying smells.
At the 2016 Alzheimer’s Association International Conference in Toronto, researchers at Columbia University Medical Center, New York, reported on a study of 397 participants with an average age of 80. The study tested the predictability of dementia transition and cognitive decline using the 40-item University of Pennsylvania Smell Identification Test (UPSIT). The test involved a scratch-and-sniff test of familiar scents like turpentine, lemon, licorice, and bubble gum. Participants were followed for four years. Their conclusions were that odor identification impairments were predictors of the transition to dementia.
How You Can Help
Smell ensures we maintain our personal hygiene and offers us an essential interaction with the world around us. Smell is essential for giving us pleasure from simple things such as flowers and food. For many people smell also helps to re-create memories.
Declines in the sense of smell are not obvious to detect. Although smell is not directly life threatening, it can still impact one’s quality of life. Nutrition and safety concerns are heavily linked to smell. People who have total or partial loss of the sense of smell are almost twice as likely to have some kinds of accidents than people who have normal smell function: cooking-related accidents; exposure to an undetected fire or gas leak; eating or drinking spoiled foods or toxic substances.
1) A Medical Checkup
Since changes in a person’s smell can occur for numerous reasons, schedule a medical checkup to ensure that there is no tumor, polyps, physical blockage or condition that might require treatment.
2) Preventing a Fire or Gas Leak
Your loved one may not be able to tell or smell that he or she left something burning on the stove or that gas is leaking and causing danger. Place sensors in their houses that can detect and warn of gas or smoke, and ones that can pick up the odor of dangerous airborne chemicals. Make sure smoke detectors are still working and change batteries on a regular basis. There are also items such as the “Fire Avert” detector. This invention detects a stove fire by smoke rather than heat. When triggered by the sound of a smoke detector, it shuts off power to the stove. (See below for description details.)
3) Labels on Bleach and Other Chemicals
Make sure that bottles of bleach, ammonia, and other chemicals are clearly marked in large letters, or kept locked away so they are not mistaken for liquids to drink.
4) Ensuring a Healthy Appetite
About 95% of what we think is taste is actually smell. With loss of smell, foods may taste different or have little or no taste. Plan meals that contain foods with different flavors, spices, and textures (e.g. creamy, crispy, crunchy). Try experimenting with a variety of spices and fresh herbs. To prevent malnutrition, ensure that the food your loved one consumes has appropriate levels of vitamins and nutrients.
5) Marinate Meat and Fish
One way to add a lot of flavor to meats and fish is to soak them in a marinade for a few hours or even overnight. Grocery stores carry a variety of prepared marinades, or you can make your own with simple pantry ingredients. Keep any foods in the refrigerator when they’re being marinated so that they remain safe to eat. Once the food is done marinating, cook it as you usually would and have your loved one try it. It just may be that what they previously couldn’t taste well now tastes great.
6) Preventing Food Spoilage
When shopping for food, try to buy in small portion sizes rather than bulk. If you do buy in bulk, then divide food into one-portion size individually sealed packages to store and cook. Check the pantry shelves, refrigerator and freezer at least once a week for outdated, moldy and spoiled food.
7) Daily Hygiene
Many persons with smell loss have no idea that they have body or clothing odor, even if they do the “sniff” test. If they realized this, most would be embarrassed. If just the thought of bathing or showering your loved one makes you cringe, take a look below at the California Central Chapter’s recommendations and tips.
Avoid pointing out that clothes they are wearing are dirty or smelly. This puts your loved one on the defensive and could set up an argument. Instead, remove the soiled clothing from their room at night once your loved one is sound asleep. They’ll forget about it the next morning if there’s something else handy to put on. You might also purchase identical outfits, so that one can be washed while the other is worn.
8) Mold and Mildew
When you walk into the home, is there a musty smell? Your loved one may not be able to notice this smell. It is due to mold or mildew which are both fungi spores and could become a health problem. There are cleaning solutions available on the market. Air movement is also important for removing moisture and odors.
Understanding the loss of one’s sense of smell and its associated problems will surely maximize your loved one’s quality of life, help them retain their independence longer, and even avert a dangerous accident.
I wish you peace, patience, and joy in your caregiving today and every day!
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( Sources used in preparing this article: 1. National Institutes of Health/Senior Health; 2. National Institute on Deafness and Other Communication Disorders; 3. The Monell Chemical Senses Center; 4. Alzheimer’s Association/AAIC.)
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Watch this four-minute TED-Ed animated explanation of our remarkable sense of smell: http://ed.ted.com/lessons/how-do-we-smell-rose-eveleth.
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To read more about the Fire Avert product, go to: http://www.firerescuemagazine.com/articles/print/volume-8/issue-1/professional-development/firefighter-s-invention-stops-kitchen-fires.html. This product is available through the Alzheimer Store. You can get a 10% discount by placing your order through my website: http://caregiverfamilies.com/products/.
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Find good tips on bathing with this newsletter from the California Central Chapter of the Alzheimer’s Association: http://www.alz.org/cacentral/documents/Dementia_Care_32-_The_Battle_of_the_Bathing.pdf.
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Dementia care advocate and trainer, Teepa Snow, has a short video that describes the loss of smell: https://youtu.be/j9FFLaymycg.
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This four-minute video on problems with smell is by the National Institutes of Health: http://nihseniorhealth.gov/problemswithsmell/aboutproblemswithsmell/video/smell1_na.html?intro=yes.
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