Your grandma’s brownies, the scent of rain on a pine forest, a whiff of cardamom — smells can be powerful time machines, unlocking memories almost like magic and transporting you to specific moments more vividly than vision or hearing.

But just like vision and hearing, our sense of smell diminishes with age (and as a result of infections like Covid, smoking and pollution). About 11 percent of Americans in their 50s experience trouble smelling; that number rises to 39 percent for those over 80.

When our noses lose their sharpness, our mental health often suffers too. A diminished sense of smell is associated with worsening memory, cognition and overall well-being — as well as dementia and depression.

“Our brains need a lot of olfactory stimulation in order to maintain their health,” said Michael Leon, a professor emeritus of neurobiology at the University of California, Irvine.

Fortunately, a diminished sense of smell may be reversible, perhaps by something as simple as spending some time with your spice rack.

Why smell is so important in the brain

Scientists have long recognized that a reduced ability to detect and identify scents may be an early symptom of conditions such as depression, dementia and Parkinson’s disease. You may notice, for example, that your favorite wine has somehow lost its nose, or fail to notice that food is spoiling in your fridge, said Sarah Banks, an adjunct professor of neuroscience at the University of California, San Diego. For many people, troubles with smell are among the first signs of Alzheimer’s, she added.

So, does that mean training the nose can help the mind? Some research suggests that it actually might. In one 2022 study, seniors with depression trained their noses for several months and saw their symptoms diminish, especially those who had previous smelling problems.

A smaller 2021 study of dementia patients found that smell training not only improved depression but also helped them remember words faster. Dr. Leon said the results were better than what he saw with brain-training apps. A few other small studies have suggested smell training could increase the thickness of the hippocampus, which is the brain’s memory center.

When Dr. Banks and her colleagues examined the brain scans of master sommeliers, they found that the insula (a region that processes emotions) and the entorhinal cortex (an area whose dysfunction is involved in Alzheimer’s disease) became larger the longer someone had worked in the profession.

“That’s one of the parts of the brain that normally gets a little bit thinner and smaller with age,” Dr. Banks said. “And in these guys, it was going in the opposite direction.”

Experts think one reason this happens is that the areas of the brain involved in smell are uniquely connected to parts involved in cognition, such as the prefrontal cortex.

“The olfactory system is the only sensory system that has a direct superhighway projection into the memory centers and the emotional centers of your brain,” Dr. Leon said.

So, how do you test (and train) your nose?

Any serious testing of your sense of smell is best done with an ear, nose and throat doctor. However, if you are curious, there are a few ways to assess your nose’s abilities at home. You can order a self-testing kit, which may contain scratch cards to sniff, or evaluate yourself with simple household items.

While a home test doesn’t replace an evaluation by a physician, it can still alert you to potential declines, said Thomas Hummel, a professor of olfactory sciences at the Dresden University of Technology in Germany.

Dr. Hummel’s clinic offers a 10-minute online smell evaluation you can conduct with everyday household items and that, in one study, identified 67 percent of people with smell impairments.

To take the test, pour four strong-smelling products into separate cups. (Dr. Hummel’s test uses things like wine, soap, laundry detergent, honey or coffee). Ask someone to blindfold you and offer you the cups to sniff. Give yourself one point if you can smell something and two if you can identify it.

If you score less than seven out of eight, you may have an olfactory dysfunction. But that is not necessarily an indicator of cognitive issues or mental decline, Dr. Banks said. Your smell dysfunction may be temporary, the way it can be during and after a viral infection, though it may suggest you should consult a doctor.

What’s more, poor olfactory scores can be improved. Dr. Hummel recommends his patients find four strong-smelling household items, like a spice or some toothpaste. Sniff each of them in the morning and evening for at least 30 seconds, he said. (If you can sniff more odors, more times a day and for longer than 30 seconds, all the better, he added.) You don’t need a blindfold; the point is to just become more intentional and aware of smells. Mix up the odors, if you like: One day you can sniff cinnamon, the next coffee.

If you’re looking for something more challenging, you might try a sommelier training kit. But you can even get results simply by paying mindful attention to the scents already present in your life.

When sommeliers train, Dr. Banks said, they often visit grocery stores to smell fruits and vegetables, learning the nuances of aromas. Another thing to try is a nighttime scent diffusing machine that wafts out essential oils while you sleep. One small study Dr. Leon led suggested that they can be helpful enhancing cognitive abilities.

Training your nose Dr. Hummel said, connects us in the world around. It may be that helping your brain can be as simple as taking time to smell the roses.

Marta Zaraska is the author of “Growing Young: How Friendship, Optimism and Kindness Can Help You Live to 100.”

Source link: https://www.nytimes.com/2024/06/18/well/mind/nose-mental-health-brain-smell.html