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Key points
- Study participants were aged 60 to 85 and had no prior diagnosis of dementia or memory impairment.
- Diffuser users performed better than control subjects on a test of verbal and recognition memory.
- A product for at-home use based on the trial is expected to be available in fall 2024.
The whiff of perfume that calls up the image of an old friend, the heady mix of spices that brings you back to your grandmother’s kitchen—what better evokes memories than scent?
Neurologically, aroma probably has such power over memory because the human brain processes scent information in the amygdala and hippocampus, which also encode emotional and episodic memories.
Many of us lose some of our sensitivity to odors as we age, a deficit that has been tied to dementia, cognitive decline, and even depression. But it turns out that regular exposure to a variety of different smells can not only summon up individual memories in older adults but also boost brain power in general.
When seniors used fragrance diffusers in their bedrooms for two hours every night over six months, their cognitive performance jumped a stunning 226 percent.
In the trial at the University of California, Irvine, neuroscientists distributed scent diffusers containing seven different essential oil cartridges to 43 adults aged 60 to 85 who had no prior diagnosis of cognitive impairment or dementia.
The diffusers were commercially available models bought from Diffuser World, and the essential oils in fragrances of rose, orange, eucalyptus, lemon, peppermint, rosemary, and lavender were purchased from The Essential Oil Company.
Twenty of the trial participants received full-strength fragrance cartridges, while 23 were given cartridges with only trace amounts of odorant as a control group. Each night before bed, they popped a cartridge into their diffuser so the scent could circulate while they slept.
The process was easy by design. Previous research has shown that exposing patients with dementia to 40 different odors twice daily improves both their memory and language skills, but the research team at California Irvine felt it wasn’t realistic to expect older adults, especially those with cognitive impairment, to open, sniff, and close bottles 80 times every single day.
“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,” says lead study author Cynthia Woo. “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."
Despite the simplified procedure, after six months members of the scent-enriched group performed 226 percent better than controls on a word list test, which evaluates verbal learning, retention, and recognition memory. They also reported sleeping more soundly.
MRI scans showed that scent-enriched group members had better integrity in a brain pathway called the left uncinate fasciculus, a tract that connects parts of the limbic system and weakens with age.
The study proves that the well established link between scent and memory can be harnessed in an easy, non-invasive intervention to improve memory function—and potentially ward off dementia—in seniors.
A product for at-home use based on the trial is expected to be available in fall 2024.
