Scentful Slumbers: Enhancing memory in older adults through nocturnal aromatherapy

Summary: A new study shows how nighttime aromatherapy can improve memory in older adults. Over the course of six months, subjects exposed to different natural oil scents for two hours each night led to a remarkable 226% increase in cognitive capacity.

This innovative approach exploits the known link between olfaction and memory and offers a potential non-invasive strategy to combat cognitive decline and dementia.

Key Facts:

  1. Participants exposed to nighttime aromatherapy showed a 226% increase in cognitive performance, as measured by a standard memory test.
  2. Neuroimaging revealed better integrity in the brain pathway known as the left uncinate fasciculus, which connects the memory center to the decision-making prefrontal cortex.
  3. The study confirms the direct link between the sense of smell and the brain’s memory circuitry, underscoring aromatherapy’s potential as a non-invasive memory enhancement technique.

Source: UC Irvine

When a scent wafted through the bedrooms of older adults for two hours every night for six months, the memories came flooding back.

Participants in this study from University of California, Irvine neuroscientists reaped a 226% increase in cognitive capacity compared to the control group.

The researchers say the result turns the long-known link between smell and memory into an easy, non-invasive technique to boost memory and potentially stave off dementia.

This shows an elderly woman surrounded by flowers.
The researchers say the results from their study confirm what scientists have learned about the connection between smell and memory. Credit: Neuroscience News

The team’s investigation appears in Frontiers in Neuroscience.

The project was carried out through the UCI Center for Neurobiology of Learning & Memory. It involved men and women aged 60 to 85 without memory impairment. Everyone was given a diffuser and seven cartridges, each containing a single and different natural oil.

People in the fortified group received full-strength cartridges. Control group participants were given the oils in small amounts. Participants put a different cartridge in their diffuser each night before going to bed, and it was activated for two hours while they slept.

People in the enriched group showed a 226% increase in cognitive performance compared to the control group, as measured by a vocabulary test commonly used to evaluate memory. Imaging revealed better integrity in the brain pathway called the left uncinate fasciculus.

This pathway, which connects the medial temporal lobe to the decision-making prefrontal cortex, becomes less robust with age. Participants also reported that they slept better.

Scientists have long known that the loss of olfactory capacity or the ability to smell can predict the development of almost 70 neurological and psychiatric diseases. These include Alzheimer’s and other dementias, Parkinson’s, schizophrenia and alcoholism.

There is evidence of a link between loss of smell due to COVID and consequent cognitive decline. Researchers have previously found that exposing people with moderate dementia to up to 40 different smells twice a day over a period of time boosted their memory and language skills, eased depression and improved their sense of smell.

The UCI team decided to try to turn this knowledge into an easy and non-invasive tool to fight dementia.

“The reality is that over the age of 60, the sense of smell and cognition start to fall off a cliff,” said Michael Leon, professor of neurobiology and behavior and a CNLM fellow.

“But it is not realistic to think that people with cognitive impairment can open, sniff and close 80 fragrance bottles daily. It would be difficult even for those without dementia.”

The study’s first author, project researcher Cynthia Woo, said: “That’s why we reduced the number of scents to just seven, exposing participants to just one each time, rather than the many aromas used simultaneously in previous research projects.

“By enabling people to experience the smells while they sleep, we eliminated the need to set aside time for this during the waking hours of each day.”

The researchers say the results from their study confirm what scientists have learned about the connection between smell and memory.

“The sense of air has the special privilege of being directly connected to the brain’s memory circuitry,” said Michael Yassa, professor and James L. McGaugh Chair in Neurobiology of Learning & Memory. The director of the CNLM, he served as a cooperating investigator.

“All the other senses are routed through the thalamus first. Everyone has experienced how powerful aromas are in evoking memories, even from very long ago. But unlike vision changes, which we treat with glasses and hearing aids for hearing loss, there have been no intervention for the loss of smell.”

Next, the team would like to investigate the technique’s impact on people with diagnosed cognitive loss. The researchers also say they hope the result will lead to more research into smell therapies for memory impairment.

A product based on their research and designed for people to use at home is expected to hit the market this fall.

Financing: The study was supported by Procter & Gamble.

About this news about smell and memory research

Author: Ethan Perez
Source: UC Irvine
Contact: Ethan Perez – UC Irvine
Image: Image credited to Neuroscience News

Original research: Open access.
Overnight odor enrichment using an odor diffuser improves memory and modifies the uncinate fasciculus in older adults” by Michael Leon et al. Frontiers in Neuroscience


Overnight odor enrichment using an odor diffuser improves memory and modifies the uncinate fasciculus in older adults

Objective: Cognitive loss in older adults is a growing problem in our society, and there is a need to develop inexpensive, simple, effective home treatments. This study was conducted to explore the use of nighttime olfactory enrichment to improve cognitive abilities in healthy older adults.

Methods: Male and female older adults (N = 43), aged 60-85, were enrolled in the study and randomly assigned to an olfactory-enriched group or control group. Subjects in the enriched group were exposed to 7 different odorants per week, one per night, for 2 hours using an odor diffuser. People in the control group had the same experience de minimisamounts of odorant. Neuropsychological assessments and fMRI scans were administered at the beginning of the study and after 6 months.

Results: A statistically significant improvement of 226% was observed in the enriched group compared to the control group on the Rey Auditory Verbal Learning Test, and improved function was observed in the left uncinate fasciculus, as assessed by mean diffusivity.

Conclusion: Minimal olfactory enrichment administered at night produces improvements in both cognitive and neural function. Thus, odor enrichment can provide an efficient and low-effort path to improved brain health.

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