About 1 in 15 people over age 40 smells odors that aren’t there. The disorder is annoying, but experts say it can also be a signal of something more serious.

Phantosmia — experiencing phantom odors — stinks for people who are bedeviled by the condition.

It’s not only annoying to constantly smell something nasty for no good reason, but such olfactory disorders could be a sign of a serious health problem.

About 1 in 15 Americans over age 40 answered “yes” when asked, “Do you sometimes smell an unpleasant, bad, or burning odor when nothing is there?” according to a new study from the National Institute on Deafness and Other Communication Disorders (NIDCD).

It’s the first nationwide effort to look at prevalence and risk factors for phantosmia, also known as olfactory hallucination.

Smoky or burning smells are among the most commonly reported phantosmia. While patients tend to report more unpleasant smells, some also experience sweet or pleasant odors.

“We think we’re capturing a range of experiences because we didn’t have data on severity or the extent to which people find the phantom odors disturbing or distressing,” Kathleen Bainbridge, PhD, a lead researcher on the study and epidemiologist at the NIDCD’s Epidemiology and Biostatistics Program, told Healthline. “We may be capturing some people for whom the smells are a curiosity or pesky. But there certainly are people out there for whom phantom odors are a big problem and they come to medical clinics in distress.”

The review involved more than 7,400 people who took part in the 2011-2014 National Health and Nutrition Examination Survey, published in the journal JAMA Otolaryngology-Head & Neck Surgery.

It found that phantosmia was especially common among women and those ages 40 to 60.

Interestingly, as the sense of smell tends to diminish with age, so does the prevalence of phantom smells. The NIDCD researchers found, for example, that phantosmia was more common among people ages 40 to 60 than those over age 60.

“One hypothesis is that the nerve cells responsible for detecting odors decrease in number as we age,” said Bainbridge. “So, if phantom odors are caused by overactive nerve cells, when they decrease in number, the phantom odor sensations diminish.”

Women, on the other hand, may be at higher risk simply because they have a more acute sense of smell than men do throughout adulthood.

“This greater sensitivity to odors may contribute to a greater likelihood of phantom odors, if the olfactory sensory neurons (odor-sensing nerve cells), are signaling without an environmental stimulus,” Bainbridge said.

A Swedish study published in 2017 also found that phantosmia was more common among women, affecting almost 5 percent of the 60- to 90-year-olds studied.

“[The prevalence] was surprising, yet when we compare our data with the data from the Sweden study, there is consistency,” said Bainbridge.

Self-reported head injuries, dry mouth, poor overall health, and socioeconomic status also were associated with higher risk of experiencing phantom odors in the U.S. study.

“The causes of phantom odor perception aren’t understood,” Bainbridge said.

She added the condition “could be related to overactive odor sensing cells in the nasal cavity or perhaps a malfunction in the part of the brain that understands odor signals.”

Some cases of phantosmia may be due to sinus infections or other relatively benign causes.

They could also be triggered by experiencing actual foul odors.

Whatever the cause, the condition has been associated with some serious health problems, including brain tumors, seizures, Parkinson’s disease, migraines, and mental health disorders.

“The major concern is that phantom odors, if severe or persistent, can interfere with quality of life,” said Bainbridge.

“Problems with the sense of smell are often overlooked, despite their importance. They can have a big impact on appetite, food preferences, and the ability to smell danger signals such as fire, gas leaks, and spoiled food,” Judith A. Cooper, PhD, acting director of the NIDCD, told Healthline.

Reporting phantosmia to your doctor can help determine a cause and appropriate treatment, such as an appointment with an otolaryngologist — an ear, nose, and throat specialist.

“If it’s persistent it probably needs to be evaluated,” Dr. Justin Turner, medical director at the Vanderbilt University School of Medicine’s Smell and Taste Center in Tennessee, told Healthline.

Turner noted that phantom odors are considered a subset of a group of disorders called dysosmia, which include any loss or diminishment in the sense of smell, as well as parosmia, a condition where smells are misidentified.

“When people lose their sense of smell it’s more likely to be nasal than neurological,” said Turner. “We see lots of people with chronic sinusitis who lose their sense of smell, but it’s very unusual for them to report phantosmia.”

Parosmia, on the other hand, is sometimes reported when patients are in the process of recovering their sense of smell — smelling a fire burning but registering the scent as licorice, for example.

“I personally would be more concerned with phantosmia” because of its possible relationship to errant signaling between the olfactory nerves and the brain, Turner added.

However, while interest in phantom odors has increased in recent years, a 2018 research review found few studies and little consensus about how to treat chronic phantosmia.

One small study found that 10 of 11 subjects derived some relief through surgery on the mucous lining of the nasal cavity, according to researchers at the Indiana University School of Medicine.