Opium Perfume by Yves Saint Laurent, France

In a study by neuroscientists from the University of California, Irvine, older adults were exposed to a fragrance in their bedrooms for two hours every night for six months. The results were impressive – the participants saw a 226% increase in cognitive capacity compared to the control group. This technique is non-invasive and easy to do, making it a promising way to strengthen memory and potentially prevent dementia.

The study was conducted by the UCI Center for the Neurobiology of Learning & Memory, and involved men and women aged 60 to 85 who did not have memory impairment. They all received a diffuser and seven cartridges, each containing a different natural oil. The enriched group received full-strength cartridges, while the control group received tiny amounts of the oils. Participants inserted a different cartridge into their diffuser each evening before bed, and it activated for two hours as they slept.

As measured by a word list test commonly used to evaluate memory, the enriched group showed a 226% increase in cognitive performance compared to the control group. Imaging showed better integrity in the brain pathway called the left uncinate fasciculus, which connects the medial temporal lobe to the decision-making prefrontal cortex and becomes less robust with age. Participants also reported sleeping more soundly.

Scientists have known for a long time that losing the ability to smell can indicate the development of almost 70 neurological and psychiatric diseases, including Alzheimer’s, Parkinson’s, schizophrenia, and alcoholism. There is growing evidence that losing the sense of smell due to COVID-19 may lead to cognitive decline. Previous studies have shown that exposing people with moderate dementia to up to 40 different odors twice a day can improve their memory and language skills, alleviate depression, and enhance their sense of smell. The UCI team decided to use this knowledge to create a simple and non-invasive tool to fight dementia.

“The reality is that over the age of 60, the olfactory sense and cognition starts to fall off a cliff,” said Michael Leon, professor of neurobiology & behavior and a CNLM fellow. “But it’s not realistic to think people with cognitive impairment could open, sniff and close 80 odorant bottles daily. This would be difficult even for those without dementia.”

The study’s first author, project scientist 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 multiple aromas used simultaneously in previous research projects. By making it possible for people to experience the odors while sleeping, we eliminated the need to set aside time for this during waking hours every day.”

The researchers say the results from their study bear out what scientists learned about 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 in the Neurobiology of Learning & Memory. The director of CNLM, he served as collaborating investigator. “All the other senses are routed first through the thalamus. Everyone has experienced how powerful aromas are in evoking recollections, even from very long ago. However, unlike with vision changes that we treat with glasses and hearing aids for hearing impairment, there has been no intervention for the loss of smell.”

The team plans to examine further how the technique affects those with cognitive loss. The researchers also aim to encourage more studies on using smells to enhance memory. They anticipate launching a product based on their findings for at-home use this autumn.

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).