Hyposmia


Hyposmia, or microsmia, 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.
Hyposmia might be a very early sign of Parkinson's disease. Hyposmia is also an early and almost universal finding in Alzheimer's disease and dementia with Lewy bodies. Lifelong hyposmia could be caused by Kallmann syndrome or Autistic Spectrum Disorder.

Epidemiology

The National Health and Nutrition Examination Survey collected data on chemosensory function in a nationally-representative sample of US civilian, non-institutionalized persons in 2012. Olfactory function was assessed on persons aged 40 years and older with an 8-item, odor identification test. Odors included food odors, warning odors and household odors. Olfactory function score was based on the number of correct identifications. Prevalence of anosmia/severe hyposmia was 0.3 at age 40-49 rising to 14.1 at age 80+. Prevalence of hyposmia was much higher: 3.7% at age 40-49 and 25.9% at 80+. Both were more prevalent in blacks than whites.
Chemosensory data were also collected in a larger NHANES sample in 2013-2014. The prevalence of smell disorder was 13.5% in persons aged 40 years and over. 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, male sex, black race and Hispanic ethnicity, low family income, low educational attainment, low alcohol consumption and a history of asthma or cancer were independently associated with a greater prevalence of smell impairment.