- Regular exposure to multiple scents — in other words, enhanced olfaction — has been shown to improve cognitive performance in older adults.
- However, not all studies have produced consistent results.
- A new study has found that nightly use of aromatherapy essential oils such as lavender and rose can improve word recall by 226% and improve the function of a key brain pathway that plays a key role in learning and memory.
- These findings suggest that olfactory enhancement may be a low-cost approach to alleviate neurological disorders in older adults.
In the United States, cognitive decline, characterized by confusion and memory loss,
Previous studies have shown that cognitive decline accompanies or precedes loss of smell in a variety of neurological disorders.
Several studies have shown that regular exposure to multiple scents and odorants (a practice known as olfactory enrichment) may have beneficial effects on cognitive performance in older adults.
In a new clinical study, researchers at the University of California, Irvine investigated whether a six-month nightly aromatherapy regimen could improve cognitive performance in older adults.
After enriching their sense of smell with aromatherapy oils, they observed a significant improvement in their memory for the word list, as well as improved functioning of a part of the brain called the left uncinate fasciculus.
The study was funded by Procter & Gamble.
The results of the study are: The cutting edge of neuroscience.
For the study, the researchers recruited 43 participants aged 60 to 85 who were in general health and cognitively good.
Participants were randomly split into two groups: an experimental group of 20 people were exposed to essential oils every night, while a control group of 23 people were exposed to trace amounts of essential oils.
Participants were exposed to high or low concentrations of essential oils using a nebulizing fragrance diffuser for two hours each night before going to bed for six months.
The diffuser alternated between seven scents for each day of the week: rose, orange, eucalyptus, lemon, peppermint, rosemary, and lavender from Essential Oil Company (Portland, Oregon).
All participants underwent a series of assessments at the start of the study (baseline) and after 6 months of intervention.
- Cognitive assessment, including a pattern separation test to evaluate the ability to distinguish between two similar stimuli
- Depression and Quality of Life Questionnaire
- Testing olfactory function
- Functional Magnetic Resonance Imaging (fMRI) to examine changes in brain structure and brain structural connectivity
The study found that participants in the olfactory stimulation enhancement group performed 226% better on the Rey Auditory Verbal Learning Test (a word list recall test used to assess verbal learning and memory) compared to the control group.
Additionally, functional improvement of the left uncinate fasciculus was observed, as assessed by mean diffusivity (average water diffusivity in brain tissue).
The uncinate fasciculus is a brain pathway that plays an important role in learning and memory.
The researchers concluded that providing minimal olfactory stimulation at night using an odor diffuser significantly improved verbal memory and the integrity of specific brain pathways.
“It may therefore be appropriate to start considering olfactory enhancement as a low-cost public health program to reduce neurological risk in older adults,” the authors wrote in their study.
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However, not all studies into olfactory enhancement have produced desirable results.
“These findings suggest that cognitive impairments may be a contributing factor in the development of cognitive impairment,” said Michael Leon, PhD, professor emeritus of neurobiology and behavior at the University of California, Irvine, and lead author of the study. Today’s Medical News that “[i]It is known that the loss of olfactory stimulation leads to a decline in the memory center of the brain, and we found that increasing olfactory stimulation improves memory as well as the memory center of the brain.
“Smell is the only sense that has direct access to the memory center of the brain. [aromatherapy] “It’s a good way to stimulate these centers with very little effort,” he added.
However, Dr Mark Moss, head of psychology at Northumbria University in the UK, who was not involved in the study, said: “In the current study, the nightly scent rotation provides environmental enrichment.”
“Enhanced olfaction has been shown to affect aspects of human brain structure and memory when presented during daytime studies.”
— Dr. Michael Leung
Dr Moss said the study has a number of strengths.
“Firstly, the intervention lasted for six months, so this will be a good evaluation of the long-term use of aromatherapy. The use of brain imaging helps to show how the behavioral effects are mediated at the level of brain structure and function,” he said. MNT.
“A range of cognitive tests were administered to assess various cognitive functions such as memory, working memory, attention switching and planning. A range of essential oils were used in rotation each day over the course of a week, a positive element to the study to ensure environmental enrichment,” he continued.
However, the small number of participants who contributed data to the cognitive analysis limits the reliability of our findings: due to the COVID-19 pandemic, many participants were unable or unwilling to return to the university campus for cognitive assessment at the end of the 6-month intervention.
This reduced the cognitive assessment dataset to a total of 23, of which 12 experienced olfactory enhancement and 11 were controls.
Dr Amy Spector, professor of geriatric clinical psychology at University College London, UK, who was not involved in the study, also commented that the sample size was very small and “fully powered trials are needed before any firm conclusions can be drawn”.
The fact that none of the participants had cognitive impairment means “there are limited changes in cognitive function,” she said. MNT.
“There was likely a placebo effect as well, in that the control group was given distilled water and would have known they were not receiving treatment,” Dr. Spector noted.
“Of the 12 cognitive measures analysed, only one showed a significant difference, so even if we saw a large effect on that particular variable, the potential median improvement of over 226% may be inflated. It only shows the change from baseline, so we don’t know exactly what the baseline score was,” said Dr Moss.
Overall, Dr. Moss thinks that using aromatherapy for a few hours at night is worth trying, as it “may not only improve the quality of your sleep, but also aid memory.”
However, he warned not to expect “robust improvements” because “only half of the participants in the study who received the aromatherapy intervention had improved memory after six months.”
