A new study has shown that older adults who were exposed to fragrance overnight experienced a significant improvement in their memory.

Participants’ cognitive performance improved by 226% after using a natural oil diffuser for two hours as they slept.

Researchers from the University of California, Irvine says the technique, which harnesses the known link between memory and smell, provides an easy way of boosting memory and could even help to ward off dementia.

Michael Leon, professor of neurobiology and behaviour, said: “The reality is that over the age of 60, the olfactory sense and cognition starts to fall off a cliff. 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.”

Professor Michael Yassa, James L. McGaugh Chair in the Neurobiology of Learning and Memory, went on to say: “The olfactory sense has the special privilege of being directly connected to the brain’s memory circuits. 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 study involved a group of men and women aged from 60 to 85 with no memory problems. The test group received a diffuser and seven full-strength natural oil cartridges; the control group received much smaller amounts of the oils. The participants used the diffuser for two hours each night as they slept.

The participants were then given a word list test which is used to assess memory, revealing the marked improvement in cognitive performance in people in the test group. Brain scan imagery also showed better integrity in a pathway in the brain which becomes less hardy as someone ages.

In addition, the test group participants reported that they slept better.

The study builds on previous knowledge around the connection between smell and memory. It is well-known that the ability to smell can forecast the development of almost 70 neurological and psychiatric conditions, including Parkinson’s, schizophrenia and Alzheimer’s. Scientists are also looking into a possible link between COVID-related loss of smell and subsequent cognitive decline.

Prior research found that people with moderate dementia who were exposed to up to 40 different smells twice a day during the study period experienced an improvement in their memory and language skills. It was also linked to an improvement in depression.

The first author of the latest University of California, Irvine study, project scientist Cynthia Woo, said: “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 odours while sleeping, we eliminated the need to set aside time for this during waking hours every day.”

The team are hoping to next look at how the diffuser technique may help people with cognitive loss.

Read the study in Frontiers in Neuroscience.

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