Inhaling pleasant scents while you sleep could be an effective, hassle-free way to improve brain health and help ward off dementia.
In a small study of 23 older adults aged 60 to 85 with no memory problems, neuroscientists found that inhaling odorants while sleeping could dramatically improve people’s memory over a six-month period.
“When olfactory stimulation is given, [relating to sense of smell] “When your sense of smell is enhanced, your memory regions become larger and more functional,” said study author Michael Leong, PhD, professor of neurobiology and behavior at the University of California, Irvine. “Conversely, when your sense of smell is impaired, the memory centers of the brain begin to decline.”
Essential oils to use in a diffuser during the first two hours of sleep
In this project, participants were split into two groups, and those in the olfactory enhancement group were provided with an air freshener diffuser and seven different essential oils (rose, orange, eucalyptus, lemon, peppermint, rosemary, and lavender).
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Participants were instructed to turn on the diffuser when they went to bed, and the scents were released into the air overnight for two hours from the time they fell asleep. Participants alternated between different odorants each night.
The control group was provided with an air freshener diffuser and underwent the same procedure, except that rather than essential oils, they were given a bottle of distilled water with undetectable traces of air freshener added.
Bedtime aromatherapy leads to dramatic improvements in cognitive tests
At the start and end of the study, participants completed a word list test commonly used to assess verbal learning and memory. After six months, those who received the aromatherapy treatment had a 226% increase in cognitive ability compared to the control group, according to findings recently published in the journal Neuropsychiatry. The cutting edge of neuroscience.
“Compared to a control group, participants who received ‘reinforcement’ showed improved performance on word list recall, an important test of verbal learning and memory,” the study authors wrote.
According to the authors, after six months, the following changes had occurred:
- Of the 12 participants in the aromatherapy group, 6 of 12 experienced improvements in memory compared to only 3 of 11 in the control group.
- Only 1 in 12 people in the aromatherapy group experienced a decline in cognitive ability, compared with 7 in 11 people in the control group.
- Five out of 12 people in the aromatherapy group stayed the same in terms of memory, while one out of 11 people in the control group stayed the same in terms of memory.
The study began with a total of 132 randomly selected participants, but disruptions caused by the pandemic meant there was a high dropout rate, Leong said.
The sense of smell and memory have long been linked
Although the study is small, it is consistent with other scientific findings that show a link between smell and cognitive abilities, says Jay Gottfried, M.D., a professor of neurology and psychology at the University of Pennsylvania in Philadelphia, who studies the sense of smell and its effects on the brain.
“Published research from our lab, and many others, has shown that smell can have a powerful and targeted effect on memory after sleep,” said Gottfried, who was not involved in the study.
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Moreover, the findings were based on a very small number of participants, “severely limiting our confidence in what we can learn from this,” they added.
Dr. Leon suggests that the cognitive improvements may be related to the fact that the same brain areas that process emotion, learning and memory also process smell.
“The olfactory system is the only sense that has a direct ‘superhighway’ input to the memory-central regions of the brain,” says Leong. All other senses first transmit information through the thalamus, an egg-shaped structure in the center of the brain, which then relays the information to the brain’s cerebral cortex for interpretation.
Imaging confirms aromatherapy’s effect on the brain
Leon and his colleagues also conducted brain imaging studies that showed that aromatherapy users had better brain health in a pathway called the left uncinate fasciculus, which connects the medial temporal lobe, essential for memory, with the prefrontal cortex, responsible for decision-making, and which declines in health with age.
While there was no significant difference in sleep quality between the aroma and control groups, the Sleep Foundation points out that inhaling aromas while sleeping may lead to better rest, which is essential for the formation and storage of long-term memories.
Study co-author Michael Yassa, PhD, professor of neurobiology of learning and memory at the University of California, Irvine, suggested further research may be needed into treatments that preserve the sense of smell.
“We have all experienced the powerful ability of a smell to evoke a distant memory,” he said in a statement, “but while vision impairment is treated with glasses and hearing impairment with hearing aids, there has until now been no intervention for loss of smell.”
The study authors hope that their findings will lead to further research into olfactory therapy for memory problems, and say they will next examine the effects of inhaling scents while sleeping on patients diagnosed with cognitive decline.
