First Prevalence Data on 'Phantom Odors' Show Women Often Affected

Batya Swift Yasgur, MA, LSW

August 21, 2018

More than 6% of US residents over age 40 years experience "phantom odors" — smells for which there is no external stimulus, new research shows.

Investigators studied 7400 adults who participated in the National Heath and Nutrition Examination Survey (NHANES) and found that 1 in 15 participants smelled an unpleasant odor when nothing was there to produce it.

The prevalence was greater among women, younger individuals, people of lower socioeconomic status, those with poorer health, and those with a history of head injury or dry mouth symptoms.

"This study is the first in the US to use nationally representative data to examine the prevalence of and risk factors for phantom odor perception," lead author Kathleen Bainbridge, PhD, from the Epidemiology and Biostatistics Program at the National Institute on Deafness and Other Communication Disorders, part of the National Institutes of Health, told Medscape Medical News.

"This study could inform future research aiming to unlock the mysteries of phantom odors," she said.

The study was published online August 16 in JAMA Otolaryngology-Head & Neck Surgery.

"Miserable" Quality of Life

"The perception of phantom odors is a qualitative olfactory dysfunction whereby affected individuals perceive odors in the absence of an eternal stimulus," with the odor typically described as "foul," rotten," or "chemical," the authors write.

Few epidemiologic studies have addressed this perception, and most evidence has been limited to case reports and small clinical studies, they observe.

The biological mechanism of phantom odor perception may arise from aberrant peripheral olfactory neurons that signal perception centers in the brain or from overactive brain cells that create the perception.

"We knew that phantom odor perception had been observed in medical clinics, but we did not know how common this condition was, nor what types of people are more commonly affected," Bainbridge commented.

The researchers were also motivated by the "miserable quality of life" that people with this condition experience, she said.

To investigate, the researchers used data collected between 2011 and 2014 by the NHANES conducted by the National Center for Health Statistics.

Study participants (aged ≥ 40 years) were interviewed about phantom odors and also underwent a physical examination.

Participants were asked, "Do you sometimes smell an unpleasant, bad, or burning odor when nothing is there?"

The researchers obtained information about sociodemographic characteristics, including age, sex, and educational attainment, as well as race/ethnic background.

Individuals classified as "never" having smoked were those who reported never having smoked 100 cigarettes in their lifetime. Otherwise, smoking status was defined as currently smoking every day, currently smoking some days, or former smoker.

Alcohol use was classified by using a threshold of 12 alcoholic beverages in the past year.

Participants were asked to assess their general health status as well as reporting on specific physical conditions during the past year, including nasal congestion from allergies, colds or flu lasting more than 1 month, and persistent dry mouth.

In addition, interview questions assessed lifetime history of head injury with resulting loss of consciousness, broken nose or other facial/skull injury, and more than two sinus infections.

To assess the potential presence of reduced smell function, participants were asked to identify eight odors, with reduced smell function defined as fewer than six correctly identified odorants.

Female Sex, Head Injury More Common

The researchers estimated the prevalence of phantom odor perception as 6.5% (n = 534) (95% CI, 5.7% - 7.5%).

Of those who experienced it, only 11.1% (n = 64) reported discussing a taste or smell problem of any kind with a clinician.

Those who reported phantom odors were less likely to be younger than age 70 years than those who did not report phantom odors (12.4% [n = 85] vs 19.7% [n = 1698]).

There were racial/ethnic differences between people affected by phantom odors — a greater proportion of non-Hispanic black people were represented among those who reported phantom odors.

Conversely, non-Hispanic white individuals and non-Hispanic Asian individuals were represented in greater proportions among those who did not report phantom odors compared with those who did.

The overall national sample was slightly more than half female (52.8% [n = 3862]). Of those who reported phantom odors, 68.0% (n = 356) were women.

Men in younger age groups were twice as likely to report phantom odors as men aged 70 years or older, although this association was statistically significant only for men aged 40 to 49 years

However, compared with men aged 70 years or older, women in this age group had no greater likelihood of phantom odor perception; on the other hand, women in the younger age groups (40 - 49, 50 - 59, 60 - 69 years) had 5, 6, and 3 times the odds of phantom odor perception, respectively.

Phantom odors were more common in individuals with only a high school education.

Two thirds of those (n = 762) who reported phantom odors were of lower income (income-to-poverty ration < 3) vs 46.1% of those who did not report phantom odors (n = 3749).

Over one quarter (25.3%) of those who reported phantom odors had a history of current or former cigarette smoking, compared with 17.8% of those who did not report phantom odors.

Of people classified as being in fair or poor health, more than 13% (n = 227) reported phantom odors, compared with 5.8% (n = 169) and 4.2% (n = 84) of those in good and very good/excellent health, respectively.

People with persistent dry mouth had more than three times the prevalence of reporting phantom odors vs those who did not (17.4% [n = 204] vs 4.9% [n = 330], respectively).

Of people who had sustained head injuries accompanied by loss of consciousness, 10% (n = 112) reported phantom odors, vs 5.7% (n = 422) of those without a history of head injury.

People who had sustained injuries to their nose, face, or skull had no greater prevalence of phantom odor perception, although people with reduced smell function had somewhat, but not significantly, lower prevalence.

"We found some risk factors that may be related to the perception of phantom odor — people are more likely to experienced this condition if they are female and are relatively young," Bainbridge commented.

Other risk factors included head injury, dry mouth, poor overall health, and low socioeconomic status.

She suggested that people with low socioeconomic status may "have health conditions that contribute to phantom odors, either directly or because of medications needed to treat their health conditions."

Temporary Condition

Commenting on the study for Medscape Medical News, Jeffrey D. Suh, MD, associate professor-in-residence, Department of Head and Neck Surgery, David Geffen School of Medicine at UCLA, California, who was not involved with the study, called it "important, because dysosmia can significantly impair quality of life, and because there is very little consensus in the diagnosis, management, and treatment of patients that suffer from this condition."

Greater understanding "of the incidence of phantosmias and risk factors" should enable clinicians "to better be able to diagnose and treat their treatment," said Suh, who is the coauthor of an accompanying editorial.

Study coauthor Donald Leopold, MD, clinical professor, Department of Surgery, University of Vermont Medical Center, Burlington, suggested reassuring patients that experiencing phantom odors is usually a temporary condition and resolves spontaneously in 1 year.

Treatment approaches might include blocking nasal airflow with saline, especially when applied with the head inverted, and considering a trial with antidepressants or anticonvulsants, particularly gabapentin.

The National Institute on Deafness and Other Communication Disorders provided funding support for National Health and Nutrition Examination Survey chemosensory data collection via interagency agreements with theNational Center for Health Statistics of the Centers for Disease Control and Prevention and the University of Connecticut. Support for the statistical analysis was provided by Social & Scientific Systems Inc. Bainbridge, Leopold, and the other study authors, as well as Suh and the editorial coauthor, have disclosed no relevant financial relationships.

JAMA Otolaryngol Head Neck Surg. Published online August 16, 2018. Abstract, Editorial

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