Scents have the power to catapult you smack dab into the middle of a strong memory. Maybe the sharp chemical smell of chlorine takes you back to summers at the pool. Or the smell of wet sidewalks after a rain shower sparks the memory of walking down a city street.
One new study published in Frontiers in Neuroscience in July of this year suggests that our nose may not only spark memory but improve it. (1) “There has always been an intriguing correlation between the olfactory cortex, which governs smell, and dementia,” Dr. June Seliber-Klein, MD, neurology and sleep board-certified physician based in Monterey, CA tells Sleepopolis. “Often, one of the first symptoms of dementia is a loss of the sense of smell.” (2,3)
As the baby boomer generation ages, dementia is expected to spike. Experts reported about seven million Americans had dementia in 2020. If the trend continues, that number may reach 12 million by 2040.
This new study done by researchers at the University of California, Irvine (UCI) wanted to see if they could improve memory in older adults by adding scent to their sleep. Their results say it worked. “…We found the largest improvement in memory of healthy older adults with a procedure that doesn’t take much effort and is done while people are sleeping,” Dr. Michael Leon, PhD, study co-author and professor of neurobiology and behavior at UCI tells Sleepopolis.
Many health providers use the “smell test” as one clue to catch impending dementia early. (4) “This study employs a clever approach,” says Seliber-Klein. Instead of diagnosing dementia with smell, they tried to find out if they could use smell to treat or prevent cognitive decline.
How They Did It
Forty-three adults aged 60 to 85 agreed to be part of this study. The control group of 23 people slept with no scent, while the other 20 were subjected to smell during sleep. These 20 were exposed to seven different scents per week, one per night, for two hours at the beginning of their sleep.
After six months, the study authors did assessments on each participant to test for brain function. “The tool used to evaluate cognitive function was an auditory verbal learning test, which involved recalling a word list,” says Seliber-Klein.
“This testing of word list recall is clinically relevant, similar to remembering a grocery list made at home before going to the store.” Each also had an MRI scan done at the beginning and end of the study to check for changes in the brain.
The Results Are In
At the six-month mark, the group who smelled the smells demonstrated a 226 percent difference from the control group when taking the Rey Auditory Verbal Learning Test (RAVLT).
“The researchers correlated these behavioral tests with MRI scans, which demonstrated the stimulation of a brain region involved in both smell and cognitive function,” Seliber-Klein says. Other studies have found similar effects, with “smell therapy” showing psychological benefits.
This small study suggests we may be able to prevent or slow memory loss through smell therapy, or olfactory therapy. This method is inexpensive, easy, and can be done at home. If proven effective, patients of all means could have access to it.
While this study suggests some exciting possibilities, more research in this area is needed. This study was limited by a small sample size and a high rate of participants dropping out, Dr. Bruce Bassi, MD, a psychiatrist based in Chicago, tells Sleepopolis. The UCI team measured member participation by weighing the bottles of scent afterward, but Bassi says he would have liked to see the participation from the control group as well.
“The study was interrupted by the COVID-19 pandemic, which created some difficulties, and therefore, the study will need to be replicated. Nonetheless, I believe that valuable data still exists,” Seliber-Klein says.
Can I Try It?
If you worry about losing memory, you may want to try this method immediately. As with new therapies of any kind, it’s always best to check with your healthcare provider first. “I won’t be making a generalized recommendation to my patients based on the outcome of this study but I would say it is a low-risk type of activity for patients, and if they feel it is relaxing and helpful for sleep, then they may decide to continue doing it,” says Bassi.
“I would recommend olfactory enrichment for older adults,” Leon says, “as their memory and olfactory ability start to fall at just about the same time – 60 years old.” He and a team are working on a device that releases scents while you sleep, with the goal of improving memory.
“Based on this and other studies, I would definitely recommend olfactory stimulation,” says Seliber-Klein. “Introducing olfactory stimulation carries no downsides, so I highly recommend it.” In other words, even if it doesn’t work for you, smell therapy has very little chance of hurting you. Talk it over with your provider if you’d like, but otherwise, find some scents that you like and enjoy!
1. Woo, Cynthia, C.; Miranda, Blake; Sathishkumar, Mithra; Dehkordi-Vakil, Farideh; Yassa, Michael A.; Leon, Michael; “Overnight olfactory enrichment using an odorant diffuser improves memory and modifies the uncinate fasciculus in older adults,” Frontiers; July 24, 2023.
Seliber-Klein, June. Author interview. August 2023.
2. Kamath, Vidyulataa; Senjem, Matthew L.b; Spychalla, Anthony J.; Chen, Honglei ; Palta, Priya; Mosley, Thomas H.; Windham, B. Gwen; Griswold, Michael; Knopman, David S.; Gottesman, Rebecca F.; Jack Jr, Clifford R.; Sharrett, A. Richey; Schneider, Andrea L.C., “The Neuroanatomic Correlates of Olfactory Identification Impairment in Healthy Older Adults and in Persons with Mild Cognitive Impairment,” Journal of Alzheimer’s Disease, June 17, 2022.
3. “Sense of smell linked to speed of brain loss and cognitive decline,” National Institute on Aging, March 30, 2023.
4. Brai Emanuele, Hummel Thomas, Alberi Lavinia; “Smell, an Underrated Early Biomarker for Brain Aging,” Frontiers in Neuroscience, 2020.
Leon, Michael. Author interview. August 2023.
Bassi, Bruce. Author interview. August 2023.