A new study reveals that 1 in 15 Americans (6.5 percent) over the age of 40 experiences phantom odors — smells that aren’t actually there.

As we age, our ability to identify odors tends to decrease. Phantom odor perception, on the other hand, seems to increase with age. In a previous Swedish study, for example, researchers found that 4.9 percent of people over the age of 60 experienced phantom odors. It also found a higher prevalence in women than men.

The new study, published in the journal JAMA Otolaryngology-Head and Neck Surgery, found a similar prevalence in the over-60 age group. But when the researchers expanded to a broader age range, they discovered an even higher prevalence among people between the ages of 40 and 60.

The new findings also show that about twice as many women as men reported phantom odors, and that the female predominance was particularly striking for those under age 60.

Donald Leopold, M.D., one of the study’s authors and clinical professor in the department of surgery at University of Vermont Medical Center, Burlington, says that people who perceive strong phantom odors often have a miserable quality of life, and sometimes cannot maintain a healthy weight.

“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,” said Judith A. Cooper, Ph.D., acting director of the National Institute on Deafness and Other Communication Disorders (NIDCD).

For the study, the researchers looked at data from 7,417 participants over the age of 40 from the 2011-2014 National Health and Nutrition Examination Survey (NHANES). The NHANES data were collected by the National Center for Health Statistics, which is part of the Centers for Disease Control and Prevention.

Researchers used the following NHANES survey question to determine whether participants had experienced phantom odor perception: “Do you sometimes smell an unpleasant, bad, or burning odor when nothing is there?”

To further investigate the correlation between phantom odors and participant characteristics, the researchers looked at participants’ age, sex, education level, race/ethnicity, socioeconomic status, certain health habits and general health status.

Apart from age and gender, other risk factors for the onset of phantom odors included head injury, dry mouth, poor overall health, and low socio-economic status.

The researchers hypothesize that people with lower socioeconomic status may more commonly be exposed to environmental pollutants and toxins, or have health conditions that contribute to phantom odors, either directly or because of medications needed to treat their health conditions.

The study is the first in the United States to use nationally representative data to investigate the prevalence of and risk factors for phantom odor perception. The new findings could inform future research focused on unlocking the mysteries of phantom odors.

“The causes of phantom odor perception are not understood. 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,” said study leader Kathleen Bainbridge, Ph.D., of the Epidemiology and Biostatistics Program at the NIDCD.

“A good first step in understanding any medical condition is a clear description of the phenomenon. From there, other researchers may form ideas about where to look further for possible causes and ultimately for ways to prevent or treat the condition.”

Source: NIH/National Institute on Deafness and Other Communication Disorders