SARAH MCCAMMON, HOST:
OK. If you can, stop what you're doing, breathe in through your nose. What do you smell? Well, if you're lucky, it's morning coffee. But for a lot of us, the answer might be not all that much. Researchers say many in the U.S. are deprived of smells, that we've come to expect an odorless world. And a new study suggests our learning and memory might be well served if we were exposed to more smells as we age. NPR's Pien Huang reports.
PIEN HUANG, BYLINE: Michael Leon is a neurobiologist. He's a professor emeritus at University of California, Irvine. And as an experiment, he gave a few dozen healthy, older adults diffusers, machines that release smells in a room, and also different essential oils to go in them.
MICHAEL LEON: So rose, orange, eucalyptus, lemon, peppermint, rosemary and lavender.
HUANG: Each night, a different scent would waft through the bedroom. And over the course of six months, there was a 226% improvement on a learning and memory test among those who slept with a strong nightly scent compared with those that diffused distilled water every night. Leon says the scents were stimulating the memory centers of people's brains as they slept. The results were published recently in the journal Frontiers in Neuroscience. Now, the study was small, just 43 people. And their data collection got interrupted by the pandemic. Still, Leon says, it jibes with the understanding of how smell is connected to learning and memory.
LEON: Most people who live in our affluent society are actually deprived chronically of the odor stimulation that their brain needs.
HUANG: This living in a scent-free world, combined with the wear and tear that comes with aging, means that around the time people turn 60, their sense of smell and memory starts declining together. In a previous study, researchers in Korea found that twice-daily intensive smell therapy can help improve memory and attention in those with moderate dementia. Leon's study was testing more passive ways to stimulate the brain.
LEON: The idea is that it will keep the memory centers of your brain in good condition throughout life and perhaps prevent memory loss older in life.
HUANG: Leon says there's definitely more research to be done, but he thinks there's enough evidence to try this at home. He thinks almost everyone can get more smells into their lives. Pien Huang, NPR News. Transcript provided by NPR, Copyright NPR.
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