{{short description|Reduced ability to smell and to detect odors}} {{more citations needed|date=December 2010}} '''Hyposmia''', or '''microsmia''',<ref>{{Cite book| last = Hawkes| first = Christopher H.| date = 2002| title = Smell and taste complaints| publisher = Butterworth-Heinemann| location = Boston| isbn = 0-7506-7287-0|pages=49–50}}</ref> is a reduced ability to smell and to detect odors. A related condition is anosmia, in which no odors can be detected. Some of the causes of olfaction problems are allergies, nasal polyps, viral infections and head trauma. In 2012 an estimated 9.8 million people aged 40 and older in the United States had hyposmia and an additional 3.4 million had anosmia/severe hyposmia.<ref>{{cite journal |last1=Hoffman |first1=Howard J. |last2=Rawal |first2=Shristi |last3=Li |first3=Chuan-Ming |last4=Duffy |first4=Valerie B. |title=New chemosensory component in the U.S. National Health and Nutrition Examination Survey (NHANES): first-year results for measured olfactory dysfunction |journal=Reviews in Endocrine and Metabolic Disorders |date=10 June 2016 |volume=17 |issue=2 |pages=221–240 |doi=10.1007/s11154-016-9364-1|pmid=27287364 |pmc=5033684 }}</ref>
Hyposmia is considered a form of olfactory dysfunction and is more common than complete loss of smell. It may be temporary or long term depending on the underlying cause<ref name=":1">{{Cite web |date=July 31, 2023 |title=Smell (Olfactory) Disorders, Anosmia, Phantosmia & Others |url=https://www.nidcd.nih.gov/health/smell-disorders |url-status=live |access-date=March 30, 2026 |website=National Institute on Deafness and Other Communication Disorders}}</ref><ref name=":0">{{Cite web |title=Overview of Smell and Taste Disorders |url=https://www.merckmanuals.com/home/ear-nose-and-throat-disorders/symptoms-of-nose-and-throat-disorders/overview-of-smell-and-taste-disorders |url-status=live |access-date=March 30, 2026 |website=Merck Manual}}</ref>
Hyposmia is relatively common, particularly in older adults, and population studies suggest that a significant portion of individuals over the age of 40 experience some degree of reduced olfactory function.<ref name=":2" />
Hyposmia might be a very early sign of Parkinson's disease.<ref name=factor>Factor, Stewart A., & Weiner, William J., eds. (2008). ''Parkinson's Disease: Diagnosis and Clinical Management'', 2nd ed., pp. 72-73. New York: Demos Medical Publishing.</ref> Hyposmia is also an early and almost universal finding in Alzheimer's disease and dementia with Lewy bodies.<ref name=factor/> Lifelong hyposmia could be caused by or comorbid with Kallmann syndrome<ref>{{cite journal |last1=Arkoncel |first1=ML |last2=Arkoncel |first2=FR |last3=Lantion-Ang |first3=FL |title=A case of Kallmann syndrome |journal=BMJ Case Reports |date=March 2011 |volume=2011 |pages=bcr0120113727 |doi=10.1136/bcr.01.2011.3727 |pmid=22700069 |pmc=3070321 |quote=Kallmann syndrome (KS), a rare genetic disorder, refers to the association between hypogonadotropic hypogonadism and anosmia or hyposmia due to abnormal migration of olfactory axons and gonadotropin-releasing hormone producing neurons.}} {{open access}}</ref> or autism.<ref>{{cite journal |last1=Tonacci |first1=Alessandro |last2=Billeci |first2=Lucia |last3=Tartarisco |first3=Gennaro |last4=Ruta |first4=Liliana |last5=Muratori |first5=Filippo |last6=Pioggia |first6=Giovanni |last7=Gangemi |first7=Sebastiano |title=Olfaction in autism spectrum disorders: A systematic review |journal=Child Neuropsychology |date=2 January 2017 |volume=23 |issue=1 |pages=1–25 |doi=10.1080/09297049.2015.1081678 |pmid=26340690 |s2cid=143375600 |url=https://www.tandfonline.com/doi/full/10.1080/09297049.2015.1081678 |issn=0929-7049|url-access=subscription }}</ref> Along with other chemosensory disturbances, hyposmia can be a key indicator of COVID-19.<ref>{{cite journal | vauthors = Lechien JR, Chiesa-Estomba CM, De Siati DR, Horoi M, Le Bon SD, Rodriguez A, Dequanter D, Blecic S, El Afia F, Distinguin L, Chekkoury-Idrissi Y, Hans S, Delgado IL, Calvo-Henriquez C, Lavigne P, Falanga C, Barillari MR, Cammaroto G, Khalife M, Leich P, Souchay C, Rossi C, Journe F, Hsieh J, Edjlali M, Carlier R, Ris L, Lovato A, De Filippis C, Coppee F, Fakhry N, Ayad T, Saussez S | display-authors = 6 | title = Olfactory and gustatory dysfunctions as a clinical presentation of mild-to-moderate forms of the coronavirus disease (COVID-19): a multicenter European study | journal = European Archives of Oto-Rhino-Laryngology | volume = 277 | issue = 8 | pages = 2251–2261 | date = August 2020 | pmid = 32253535 | pmc = 7134551 | doi = 10.1007/s00405-020-05965-1 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Xydakis MS, Dehgani-Mobaraki P, Holbrook EH, Geisthoff UW, Bauer C, Hautefort C, Herman P, Manley GT, Lyon DM, Hopkins C | display-authors = 6 | title = Smell and taste dysfunction in patients with COVID-19 | journal = The Lancet. Infectious Diseases | volume = 20 | issue = 9 | pages = 1015–1016 | date = September 2020 | pmid = 32304629 | pmc = 7159875 | doi = 10.1016/S1473-3099(20)30293-0 | doi-access = free }}</ref>
In everyday life, a reduced sense of smell may affect appetite, food enjoyment, and the ability to detect environmental hazards such as smoke or gas leaks. Some individuals may also have difficulty recognizing familiar odors.<ref name=":0" />
== Signs and symptoms == People with hyposmia typically experience a decreased sensitivity to odors, meaning that smells may appear faint or more difficult to identify. Because smell contributes significantly to taste perception, individuals may also notice that flavors seem dull or less distinct.<ref name=":0" />
This reduced sensory input can lead to decreased appetite, changes in eating habits, or reduced enjoyment of food. In addition, hyposmia may be present safety concerns, as individuals may not detect warning odors such as smoke, natural gas, or spoiled food.<ref name=":0" />
== Causes == These conditions may interfere with the ability of odor molecules to reach olfactory receptors or disrupt how olfactory signals are transmitted to and processed by the brain. For example, inflammation or blockage in the nasal passages can physically limit odor detection, while neurological factors may impair signal interpretation<ref name=":1" /><ref name=":2" />
In some cases, hyposmia is related to changes in brain function rather than obstruction of the nasal passages. This may occur when the neural pathways responsible for processing smell are affected.<ref name=":3" /><ref name=":2" />
Upper respiratory infections are among the most common temporary causes of hyposmia, and many individuals recover their sense of smell as inflammation resolves. However, in some cases the condition may persist or the exact cause may remain unclear.<ref name=":1" />
==Epidemiology== The National Health and Nutrition Examination Survey (NHANES) collected data on chemosensory function (taste and smell) in a nationally-representative sample of US civilian, non-institutionalized persons in 2012.<ref>{{cite journal |last1=Hoffman |first1=Howard J. |last2=Rawal |first2=Shristi |last3=Li |first3=Chuan-Ming |last4=Duffy |first4=Valerie B. |title=New chemosensory component in the U.S. National Health and Nutrition Examination Survey (NHANES): first-year results for measured olfactory dysfunction |journal=Reviews in Endocrine and Metabolic Disorders |date=10 June 2016 |volume=17 |issue=2 |pages=221–240 |doi=10.1007/s11154-016-9364-1|pmid=27287364 |pmc=5033684 }}</ref> Olfactory function was assessed on persons aged 40 years and older with an 8-item, odor identification test (Pocket Smell Tests, Sensonics, Inc., Haddon Heights, NJ). Odors included food odors (strawberry, chocolate, onion, grape), warning odors (natural gas, smoke) and household odors (leather, soap). Olfactory function score was based on the number of correct identifications. Prevalence (%) of anosmia/severe hyposmia (scores 0 to 3) was 0.3 at age 40–49 rising to 14.1 at age 80+. Prevalence of hyposmia (scores 4 to 5) was much higher: 3.7% at age 40–49 and 25.9% at 80+. Both were more prevalent in individuals of African descent than in those of Caucasian descent.
Chemosensory data were also collected in a larger NHANES sample in 2013–2014. The prevalence of smell disorder (scores 0–5 out of 8 correct) was 13.5% in persons aged 40 years and over.<ref>{{cite journal |last1=Liu |first1=Gang |last2=Zong |first2=Geng |last3=Doty |first3=Richard L |last4=Sun |first4=Qi |title=Prevalence and risk factors of taste and smell impairment in a nationwide representative sample of the US population: a cross-sectional study |journal=BMJ Open |date=9 November 2016 |volume=6 |issue=11 |article-number=e013246 |doi=10.1136/bmjopen-2016-013246|pmid=28157672 |pmc=5129069 |doi-access=free }}</ref> If the same prevalence occurred in 2016, an estimated 20.5 million persons 40 and over had hyposmia or anosmia. In addition multiple demographic socioeconomic, and lifestyle characteristics were assessed as risk factors for diminished smell. In statistical analyses, greater age and male sex, coupled with either black and/or non-Hispanic ethnicity, low family income, low educational attainment, high alcohol consumption (more than 4 drinks per day), and a history of asthma or cancer were independently associated with a greater prevalence of smell impairment.
== Diagnosis == Diagnosis of hyposmia is typically based on medical history and clinical evaluation. In some cases, standardized smell identification tests are used to assess a person's ability to detect and recognize odors. These tests help distinguish hyposmia from other olfactory disorders and may assist in identifying underlying causes.<ref name=":3">{{Cite web |last=Su |first=B. |date=2021 |title=Clinical Implications of Psychophysical Olfactory Testing |url=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8012732/ |url-status=live |access-date=March 30, 2026 |website=PubMed Central}}</ref> <ref name=":2">{{Cite web |last=Luke |first=L. |date=2022 |title=Investigations and Outcomes for Olfactory Disorders |url=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9707095/ |url-status=live |access-date=March 30, 2026 |website=PubMed Central}}</ref>
==See also== *Hyperosmia *Dysosmia *Anosmia
==References== {{Reflist}}
{{Cognition, perception, emotional state and behaviour symptoms and signs}}
Category:Olfaction