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Anosmia

Overview

Anosmia is defined as the lack of or diminished capacity to smell. 
Approximately 20% of the population suffers from a loss of sense of smell. This can be temporary or permanent, depending on the cause. The loss of sense of smell can have significant impacts on one&#39;s quality of life. Moreover, it can result in a reduced perception of odors and a diminished sense of taste. Anosmia can sometimes occur with ageusia - a complete loss of taste. 
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The sense of smell typically decreases with age. This is why nearly a quarter of men aged 60-69 years have a smell disorder, while 11% of women in that age group report problems with their sense of smell<a href="#accordion">[9]</a>&nbsp;<a href="#accordion">[8]</a>. A study conducted among adults in the United States found the highest prevalence of anosmia associated with the male gender and older age<a href="#accordion">[10]</a>.

Although anosmia may be associated with old age, the loss of sense of smell may point to something serious, such as brain tumors. However, a simple cold or flu can also cause anosmia in people. The recent <a href="https://merisehat.pk/disease/covid-19">COVID-19</a> pandemic resulted in a significant number of people suffering from anosmia. A study conducted among Pakistani COVID-19 cases found anosmia in 43.75% of the patients<a href="#accordion">[11]</a>. Another study, conducted among the Indian population during COVID-19, found a prevalence of 30.19%<a href="#accordion">[1]</a>.

In rare cases, people may be born with anosmia. This is called congenital anosmia and affects approximately 1 in 10,000 people<a href="#accordion">[3]</a>. 
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Anosmia has no clear subcategories. 
&nbsp;

Signs & Symptoms

Anosmia can cause people to lose their sense of smell gradually or unexpectedly. They may notice a difference in the smell of familiar scents before developing a complete loss of smell. 
&nbsp;

The following signs and symptoms are commonly associated with anosmia:

<ul>
	<li>An inability to detect familiar or strong odors</li>
	<li>No reaction to normally unpleasant odors</li>
	<li>Reduced enjoyment of food due to a lack of taste</li>
	<li>In some cases, a loss of taste can also occur along with anosmia 
	&nbsp;</li>
</ul>

Causes

The perception of odors is a complex process that involves several physiological mechanisms. Olfactory receptor cells located in the olfactory epithelium of the nose detect the odor molecules. When an odor molecule binds to these receptors, a signal is transmitted to the olfactory bulb in the brain, where the odor is interpreted and identified. Any disruption to this process, including nasal congestion, blockages in the nasal passages, or damage to the olfactory receptor cells, can lead to a reduction or loss of the sense of smell. 
&nbsp;

The following factors play a role in causing anosmia:

<ul>
	<li>Upper Respiratory Infections: Common colds, sinusitis, and other infections can cause temporary anosmia.</li>
	<li>Trauma To The Nose Or Head: A blow to the head or a broken nose can damage the olfactory nerve and cause anosmia.</li>
	<li>Neurodegenerative Disorders: <a href="https://merisehat.pk/disease/alzheimers-disease">Alzheimer&#39;s disease</a>, <a href="https://merisehat.pk/disease/parkinsons-disease">Parkinson&#39;s disease</a>, and <a href="https://merisehat.pk/disease/multiple-sclerosis">multiple sclerosis</a> can cause a progressive loss of the sense of smell.</li>
	<li>Chronic Nasal Conditions: Chronic nasal conditions, such as nasal polyps, can interfere with the ability to smell.</li>
	<li>Medications: Some medications, such as antidepressants and blood pressure medications, can cause a temporary or permanent loss of the sense of smell.</li>
	<li>Aging: As people age, the sense of smell can decline, leading to a decreased ability to perceive odors.</li>
	<li>Exposure&nbsp;To Harmful Substances: Exposure to certain chemicals, such as pesticides, solvents, and anesthetics, can damage the olfactory nerve and cause anosmia.</li>
	<li>Inherited Anosmia: Congenital anosmia is a condition in which a person is born without the ability to smell and can be either isolated or associated with a genetic disorder. The cause of isolated congenital anosmia is often unknown, but some familial cases have been reported. 
	&nbsp;</li>
</ul>

Note: If you experience a sudden onset of anosmia, contact a healthcare professional as it can be a symptom of a more serious underlying condition. 
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The loss of sense of smell is a subjective feeling, Therefore, several self-reported questionnaires and tests have been used to screen for anosmia. The National Health and Nutrition Examination Survey (NHANES) recommends the self-reported olfactory function index to screen for anosmia<a href="#accordion">[8]</a>. Researchers have also explored the use of the Q-Sticks test<a href="#accordion">[12]</a>. This involves presenting three odors (coffee, rose, and cloves) in felt-tip pens. The individuals then receive a multiple-choice list from which they identify the odor. They are given scores from 0 (no odors identified) to 3 (all odors identified).&nbsp; 
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Another screening test commonly used to identify olfactory dysfunction is the Sniffin&rsquo; Sticks test - 12 items (SST-12). The screening tool includes odors such as peppermint, banana, cinnamon, apple, lemon, orange, fish, leather, rose, cloves, coffee, licorice, pineapple, anise, garlic, and turpentine. Individuals are blindfolded and presented with 16 odorant sticks separated by 20-second intervals to prevent olfactory desensitization. Anosmia is defined as the identification of 6 or fewer odors out of the 16. SST-12 has helped researchers screen for post-COVID-19 olfactory disorders<a href="#accordion">[13]</a>. 
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Diagnosis

Measuring the degree of &#39;smell loss&#39; is challenging since smell is a subjective feeling. However, diagnosis of anosmia typically involves a combination of physical examination, medical history review, and tests. During a physical examination, the doctor will examine the nose and sinuses for any polyps, blockages, or inflammation. An otolaryngologist also called an ENT doctor, will also assess the ear and throat. 
&nbsp;

The following tests may be used to diagnose anosmia: 
&nbsp;

<ul>
	<li>Smell Test: A smell test involves presenting the individual with a series of common odors, such as coffee or soap, to determine their ability to smell. The scratch and sniff test is commonly used to test smell. A booklet of pages containing tiny beads filled with specific odors is presented to the patient. They are asked to scratch each page and identify the odor. An inability to smell the odor or identify them correctly typically indicates a smell disorder or an impaired ability to smell.</li>
	<li>MRI Or CT Scan: These scans help evaluate the brain and nasal cavity for abnormalities that can cause anosmia.</li>
	<li>Nasal Endoscopy:&nbsp;This allows doctors to visualize the nose internally and looks for any polyps or growths.</li>
	<li>Neurological Examination: A doctor may perform a neurological examination to evaluate the function of the olfactory nerve and determine if there are any signs of a neurological condition.</li>
	<li>Blood Tests: Blood tests can be used to check for underlying medical conditions, such as an autoimmune disorder, that could be causing anosmia.</li>
	<li>Olfactory Nerve Biopsy: In rare cases, a small sample of the olfactory nerve may be taken for examination under a microscope to determine if there is any damage to the nerve. 
	&nbsp;</li>
</ul>

Treatment

The treatment of anosmia depends on the underlying cause. If the loss of smell is caused by a cold, allergy, or sinus infection, it usually resolves on its own within a few days. Some common treatments include: 
&nbsp;

<ul>
	<li>Medical Treatments: Medications, such as nasal corticosteroids can be used to reduce inflammation and treat conditions like nasal polyps. Antibiotics can be used to treat infections.</li>
	<li>Surgical Treatments: Endoscopic sinus surgery may be necessary to remove physical obstructions such as nasal polyps, and restore the sense of smell.</li>
	<li>Aromatherapy: Some people have reported improvement in their sense of smell after using essential oils.</li>
	<li>Smell Training: There are various smell training programs available that may help to re-educate the brain and improve the sense of smell. It involves sniffing four different odors twice a day for several seconds over a period of 4 months. People with anosmia related to infection or head injury may benefit from smell training. 
	&nbsp;</li>
</ul>

Note: It&#39;s important to seek medical attention if you suspect you have anosmia, as prompt diagnosis and treatment can improve the chances of a successful outcome. 
&nbsp;

Anosmia can lead to several complications, including: 
&nbsp;

<ul>
	<li>Malnutrition as the person might lose interest in food and eating</li>
	<li>Reduced quality of life and enjoyment of food</li>
	<li>Increased risk of burns, fire, and smoke inhalation</li>
	<li>Difficulty detecting hazardous chemicals and gasses</li>
	<li>Difficulty detecting spoiled food, leading to food poisoning</li>
	<li>Increased risk of falls in older adults, due to impaired ability to detect obstacles</li>
	<li>Difficulty detecting certain medical conditions, such as infections or high blood sugar levels in diabetics 
	&nbsp;</li>
</ul>

The following factors have been shown to increase the risk of anosmia: 
&nbsp;

<ul>
	<li>Older age</li>
	<li>Head and nose trauma</li>
	<li>Neurodegenerative disorders, such as Parkinson&rsquo;s</li>
	<li>Smelling or consuming harmful substances 
	&nbsp;</li>
</ul>

Preventing anosmia can be challenging as some factors, such as aging and inherited genetic disorders, cannot be prevented. However, some steps can be taken to reduce the risk of developing anosmia or reduce its impact: 
&nbsp;

<ul>
	<li>Avoid exposure to hazardous chemicals and pollutants, and use proper protective equipment when handling them.</li>
	<li>Treat nasal and sinus infections promptly to prevent chronic inflammation.</li>
	<li>Avoid head trauma by wearing protective gear when engaging in activities, such as sports.</li>
	<li>Consult with a healthcare professional before starting any new medications, and discuss any potential side effects, including anosmia.</li>
	<li>Manage underlying medical conditions, such as Parkinson&#39;s disease, to reduce the risk of anosmia as a complication.</li>
	<li>Maintain good overall health through diet, exercise, and stress management. 
	&nbsp;</li>
</ul>

In a recent study published in the journal Science Transitional Medicine, researchers looked at nasal tissue samples of people with long-term loss of smell due to COVID-19 (Post-acute sequalae COVID-19). People with long-term loss of smell had immune cells called T-cells present within the samples. These cells were seen to secrete a protein called IFN-&gamma; (interferon-gamma). Researchers also noted signs of ongoing inflammation, even though the virus was no longer present. Thus, suggesting the role of the immune system in causing long-term anosmia<a href="#accordion">[2]</a>. 
&nbsp;

Key Points

<ul>
	<li>Anosmia is defined as the lack of or diminished capacity to smell.</li>
	<li>It may be either temporary or permanent, depending on the underlying cause.</li>
	<li>The sense of smell typically decreases with age. This is why nearly a quarter of men aged 60-69 years have a smell disorder, while 11% of women in that age group report problems with their sense of smell.</li>
	<li>Upper respiratory infections, neurodegenerative diseases, trauma to the head, and nasal polyps can result in anosmia.</li>
	<li>The recent COVID-19 pandemic resulted in a significant number of people suffering from anosmia. A study conducted among Pakistani COVID-19 cases found anosmia in 43.75% of the patients.</li>
	<li>The sense of smell also plays a crucial role in taste perception, as it contributes to the overall flavor experience. In the absence of a functioning sense of smell, the ability to taste is greatly reduced, with only a few basic tastes (such as sweet, salty, sour, and bitter) being distinguishable.</li>
	<li>The Q-Sticks test and the Sniffin&rsquo; Sticks test are commonly used to screen for anosmia.</li>
	<li>Measuring the degree of &#39;smell loss&#39; is challenging since smell is a subjective feeling. However, diagnosis of anosmia typically involves a combination of physical examination, medical history review, and tests.</li>
	<li>The treatment of anosmia depends on the underlying cause. If the loss of smell is caused by a cold, allergy, or sinus infection, it usually resolves on its own within a few days.</li>
	<li>Preventing anosmia can be challenging as some factors, such as aging and inherited genetic disorders, cannot be prevented. However, some steps can be taken to reduce the risk of developing anosmia or reduce its impact. 
	&nbsp;</li>
</ul>

[1] Aanand P, Angral S, Varshney S, Raj R. Incidence of Anosmia among Covid 19 patients in India. Indian J Otolaryngol Head Neck Surg. 2022;74(Suppl 2):3427-3436. doi:10.1007/s12070-021-02641-6.

[2] Dr. Chinta SidharthanDec 27 2022Reviewed by Aimee Molineux. Scientists find key reason for ongoing loss of smell in long-covid.

[3] Anosmia (lost sense of smell): Definition, causes, symptoms. Cleveland Clinic.

[4] Anosmia: Symptoms, causes, and treatments. WebMD.

[5] Cafasso J. What is anosmia? Healthline.

[6] McDermott A. Living with no sense of smell: What it's like and what you can do. Healthline.

[7] Anosmia treatment and symptoms - NY otolargyngology group. The New York Otolaryngology.

[8] Anosmia: Definition, symptoms, causes, treatment, and more. Medical News Today.

[9] Smell disorders. National Institute of Deafness and Other Communication Disorders.

[10] Dong J, Pinto JM, Guo X, et al. The Prevalence of Anosmia and Associated Factors Among U.

[11] Iqbal M, Khan SF, Khan S, Ahmad W. Prevalence of anosmia & ageusia in confirmed COVID-19 patients at teaching hospitals of District Bannu and Swat, Pakistan. INTERNATIONAL JOURNAL OF ENDORSING HEALTH SCIENCE RESEARCH (IJEHSR). 2021;9(2):217-222. doi:10.29052/ijehsr.v9.i2.2021.217-222

[12] Sorokowska A, Oleszkiewicz A, Minovi A, Konnerth CG, Hummel T. Fast screening of olfactory function using the Q-sticks test. ORL. 2019;81(5-6):245-251. doi:10.1159/000500559

[13] Vandersteen C, Payne M, Dumas L-É, et al. What about using Sniffin’ sticks 12 items test to screen post-covid-19 olfactory disorders? European Archives of Oto-Rhino-Laryngology. 2021;279(7):3477-3484. doi:10.1007/s00405-021-07148-y.