The Power of Scent
Is there a connection between smell and memory? No question, says Jayant M. Pinto, MD, a professor of surgery at the University of Chicago Medicine who studies olfactory and sinus disease. “The olfactory system is directly connected to the parts of the brain that house memory,” Dr. Pinto says. “We see this: smells can evoke strong memories, i.e., cookies your grandmother baked, your mother’s perfume, etc. This may explain why loss of smell is connected to Dementia, where memory loss is a key feature.”
The Connection Between Scent and the Brain
Dementia is a symptom cluster brought on by a number of underlying diseases that change the brain or impair blood flow to it. Having it creates problems with memory, thinking, and making decisions.
Scent—one of the five major senses—is intricately tied to the brain and memory. The olfactory bulb, which processes smell, sits just behind the nose beneath the frontal lobe. Its job is to take in scent and send signals to other parts of the brain, including those that house emotion and memory functions.
Sense of smell is associated with the size of the brain, the health of its cells, and how robust the connections are between neurons in the brain that communicate with each other. This finding was highlighted in a 2023 study in Neurology, which found that a better sense of smell is tied to a slower decline in memory, attention, processing speed, and grasping and manipulating objects.
Dementia itself doesn’t cause a loss of smell—and loss of smell doesn’t cause Dementia—but the underlying disease pathology that sometimes leads to Dementia symptoms may harm areas of the brain related to the processing of scent. In other words, loss of smell may signal changes in the brain, and loss of smell can travel with Dementia.
Could Smell Predict Dementia Risk?
More research is needed on the topic of scent and Dementia, but several recent small studies have found that loss of smell may predict who may be likely to develop Dementia. Dr. Pinto led a study at his university that found a link between rapid loss of smell in aging adults and a decline in cognitive function in areas of the brain that are important in Dementia. The study of 515 older adults was published in 2022 in Alzheimer’s & Dementia.
Other recent studies have also found a link between a decline in the sense of smell and a decline in memory. Researchers at the University of California San Francisco followed 1,794 adults ages 70 to 79 who did not have Dementia for 10 years and found that those whose sensory functions, including smell, declined even mildly showed an accelerated cognitive decline as well. Their study was published in 2020, also in Alzheimer’s & Dementia.
Aromatherapy and Dementia: What Aromatherapy May Mean for Dementia Care
The big question is: Can this connection between scent and memory be turned around to help patients with Dementia manage and control their symptoms? Research on Dementia and aromatherapy—a complementary therapy that uses essential oils from plants to help improve physical, emotional, and spiritual well-being—is sparse, but experts see it as a promising new field.
“There is some data supporting a role for smell training (a form of aromatherapy), which suggests it can be helpful for patients with decreased smell due to viral infections such as COVID-19,” Dr. Pinto says. He believes this kind of brain stimulation could possibly be extended to people with Dementia or mild cognitive impairment (a precursor to Dementia) who also have smell impairment.
An author of the 2020 study in Alzheimer’s & Dementia, Willa D. Brenowitz, PhD, MPH, an investigator at Kaiser Permanente Center for Health Research in Portland, Oregon, says, “Smell is traditionally thought to be a preclinical indicator of Dementia and neurodegeneration affecting the olfactory bulb (the main brain region that processes smell).” If that’s true, she says, it would be unlikely that aromatherapy could have any impact on those with Dementia.
However, some small recent research suggests the possibility of an important role of olfaction (the sensation of smell) in quality of life. If this were to prove to be true too, aromatherapy could possibly be shown to help calm those with Dementia. “More work is needed in this area,” Brenowitz says.
One small study led by researchers at the University of California Irvine’s Institute for Memory Impairments and Neurological Disorders shows promise that aromatherapy could someday prove to help manage Dementia. The findings were published in 2023 in Frontiers in Neuroscience. Researchers enrolled 43 men and women ages 60 to 85 who were in good health and who had no diagnosis of cognitive impairment or Dementia. One group was given an odorant diffuser and told to turn it on for 2 hours at night when they went to bed. It diffused 7 essential oils: rose, orange, eucalyptus, rosemary, peppermint, lavender, and lemon. Participants were exposed to one of the scents each night. The control group was given the same diffuser and the same instructions, but theirs contained distilled water with undetectable amounts of odor. After 6 months, the researchers found more of those exposed to the scents showed improvements in memory compared to those who were not exposed.
Researchers have also looked at the effects of aromatherapy on behavioral and psychological symptoms of Dementia. In a 2021 review of 24 studies in Dementia and Geriatric Cognitive Disorders Extra, researchers found that aromatherapy could potentially be a safe and effective therapy for people with Dementia because it appeared to improve quality of life and reduce distress. Inhalation of aromatherapy was the most common method across the studies because it works quickly and has little risk of adverse effects.
What to Know About Using Aromatherapy in Dementia
Aromatherapy has been shown to improve sleep, relieve stress, help manage pain when combined with more conventional treatments, reduce anxiety, and help provide relief from depression symptoms.
Scents that have been shown to create a sense of calm include lavender, rosemary, and orange. Other scents that may reduce stress and anxiety include chamomile, sandalwood, and rose.
For those wanting to try aromatherapy for someone with Dementia, here are some tips.
Always explain what you are doing to the person with Dementia. Let them know you are introducing scents to see if they like smelling them and how they make them feel.
Aromatherapy may be inhaled or applied to the skin.
A few drops of pure essential oils can be dropped onto a tissue, cotton ball, or warm compress and given to the person for smelling. Inhalation may also be done with a room diffuser.
To apply essential oils on the skin (such as the wrist or feet), oils should be diluted in a carrier oil, such as coconut oil or olive oil, to prevent a skin reaction. Essential oils may also be added to bath water or added to lotions. Massage (with lotion or diluted oils) could be a nice way to introduce these essential oils onto the skin.
Through trial and error, assess their response to each oil to see what type of effect it has. Some may be useful at nighttime before bed, while others may be beneficial to start the day.
Authors' opinions are not necessarily those of the Dementia Society, Inc. We do not endorse nor guarantee products, comments, suggestions, links, or other forms of the content contained within blog posts that have been provided to us with permission, paid or otherwise. Dementia Society does not provide medical advice. Please consult your doctor. www.DementiaSociety.org
Contributing Author: Beth W. Orenstein
Beth W. Orenstein is a freelance medical writer. A magna cum laude graduate of Tufts University, Orenstein has written for HealthDay, EverydayHealth, and the National Psoriasis Foundation and is a regular contributor to American Legion Magazine's Living Well and Radiology Today.
References:
Interview with Jayant M. Pinto, MD. University of Chicago.
Centers for Disease Control and Prevention. About Dementia. April 5, 2019. https://www.cdc.gov/aging/dementia/index.html
Harvard Gazette. What the nose knows: Experts discuss the science of smell and how scent, emotion, and memory are intertwined — and exploited. February 27, 2020. https://news.harvard.edu/gazette/story/2020/02/how-scent-emotion-and-memory-are-intertwined-and-exploited/
National Institute on Aging. Sense of smell linked to speed of brain loss and cognitive decline. March 30, 2023. https://www.nia.nih.gov/news/sense-smell-linked-speed-brain-loss-and-cognitive-decline
Associations of Olfaction With Longitudinal Trajectories of Brain Volumes and Neuropsychological Function in Older Adults. Neurology. February 28, 2023. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9990434/
U Chicago News. Rapid loss of smell predicts dementia and smaller brain areas linked to Alzheimer’s. July 28, 2022.
Rapid olfactory decline during aging predicts dementia and GMV loss in AD brain regions. Alzheimer’s & Dementia. April 2023. https://pubmed.ncbi.nlm.nih.gov/35899859/
Incident and faster rates of cognitive decline are associated with worse multisensory function summary scores. Alzheimer’s & Dementia. July 2020.
PDQ Cancer Information Summaries. Aromatherapy with Essential Oils.
Interview with Willa Brenowitz, PhD, MPH. Kaiser Permanente Center for Health Research.
Overnight olfactory enrichment using an odorant diffuser improves memory and modifies the uncinate fasciculus in older adults. Frontiers in Neuroscience. July 2023.
Rapid Reversal of Cognitive Decline, Olfactory Dysfunction, and Quality of Life Using Multi-Modality Photobiomodulation Therapy. Case Reports. March 2019.
Olfactory Dysfunction Predicts Subsequent Dementia in Older U.S. Adults. Journal of the American Geriatrics Society. September 2017.
Effectiveness and Safety of Aromatherapy in Managing Behavioral and Psychological Symptoms of Dementia: A Mixed-Methods Systematic Review. Dement Geriatr Cogn Dis Extra. December 2, 2021. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8739377/
National Center for Complementary and Integrative Health. Aromatherapy. January 2020.
Mental Health Association of Delaware. The Benefits of Aromatherapy. June 7, 2021. https://www.mhainde.org/the-benefits-of-aromatherapy/
Effects of aromatherapy on depression: A meta-analysis of randomized controlled trials. Gen Hosp Psychiatry. September - October, 2023. https://pubmed.ncbi.nlm.nih.gov/37619300/
University of Minnesota. Aromatherapy. https://www.takingcharge.csh.umn.edu/how-do-i-choose-and-use-essential-oils
Lippincott Nursing Center. Aromatherapy Use in the Hospital Setting: Considerations for Nurses. April 15, 2021. https://www.nursingcenter.com/ncblog/april-2021/aromatherapy-use-in-the-hospital-setting
Aromatherapy: Essential oils and nursing. American Nurse. August 9, 2021. https://www.myamericannurse.com/aromatherapy-essential-oils-and-nursing/
Comments