When a fragrance wafted through the bedrooms of older adults for 2 hours every night for six months, memories skyrocketed. Participants on this study by University of California, Irvine neuroscientists reaped a 226% increase in cognitive capability in comparison with the control group. The researchers say the finding transforms the long-known tie between smell and memory into a simple, non-invasive technique for strengthening memory and potentially deterring dementia.

The team’s study appears in Frontiers in Neuroscience. (Link to the open access study: https://www.frontiersin.org/articles/10.3389/fnins.2023.1200448/full).

The project was conducted through the UCI Center for the Neurobiology of Learning & Memory. It involved men and girls aged 60 to 85 without memory impairment. All got a diffuser and 7 cartridges, each containing a single and different natural oil. People within the enriched group received full-strength cartridges. Control group participants got the oils in tiny amounts. Participants put a special cartridge into their diffuser each evening prior to going to bed, and it activated for 2 hours as they slept.

People within the enriched group showed a 226% increase in cognitive performance in comparison with the control group, as measured by a thesaurus test commonly used to guage memory. Imaging revealed higher integrity within 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 sleeping more soundly.

Scientists have long known that the lack of olfactory capability, or ability to smell, can predict development of nearly 70 neurological and psychiatric diseases. These include Alzheimer’s and other dementias, Parkinson’s, schizophrenia and alcoholism. Evidence is emerging a couple of link between smell loss attributable to COVID and ensuing cognitive decrease. Researchers have previously found that exposing individuals with moderate dementia to as much as 40 different odors twice a day over a time frame boosted their memories and language skills, eased depression and improved their olfactory capacities. The UCI team decided to try turning this information into a simple and non-invasive dementia-fighting tool.

The truth is that over the age of 60, the olfactory sense and cognition starts to fall off a cliff. However it’s not realistic to think individuals with cognitive impairment could open, sniff and shut 80 odorant bottles each day. This might be difficult even for those without dementia.”

Michael Leon, professor of neurobiology & behavior and a CNLM fellow

The study’s first writer, project scientist Cynthia Woo, said: “That is why we reduced the variety of scents to only seven, exposing participants to only one every time, relatively than the multiple aromas used concurrently in previous research projects. By making it possible for people to experience the odors while sleeping, we eliminated the necessity to put aside time for this during waking hours day-after-day.”

The researchers say the outcomes from their study bear out what scientists learned in regards to the connection between smell and memory.

“The olfactory sense has the special privilege of being directly connected to the brain’s memory circuits,” said Michael Yassa, professor and James L. McGaugh Chair within the Neurobiology of Learning & Memory. The director of CNLM, he served as collaborating investigator. “All the opposite senses are routed first through the thalamus. Everyone has experienced how powerful aromas are in evoking recollections, even from very way back. Nonetheless, unlike with vision changes that we treat with glasses and hearing aids for hearing impairment, there was no intervention for the lack of smell.”

The team would next like to review the technique’s impact on individuals with diagnosed cognitive loss. The researchers also say they hope the finding will result in more investigations into olfactory therapies for memory impairment. A product based on their study and designed for people to make use of at home is anticipated to come back onto the market this fall.

The study was supported by Procter & Gamble.

Source:

University of California – Irvine

Journal reference:

Woo, C. C., et al. (2023) Overnight olfactory enrichment using an odorant diffuser improves memory and modifies the uncinate fasciculus in older adults. Frontiers in Neuroscience. doi.org/10.3389/fnins.2023.1200448.