AROMATHERAPY-EXPOSURE TO ESSENTIAL OILS IMPROVES MEMORY

 Benefits to mental functioning have been shown by using the techniques which are called environmental enrichments. This term encompasses the use of  different stimuli presented to the brain meant to stimulate the brain’s  activity and promote improved neural tissue  functioning.  Physical stimuli such as visual, auditory, and  muscular movements are among various stimuli being evaluated, and showing promise for facilitating memory in older adults .  (Leon and Woo, 2018; Chan et al., 2022). Stimulating the sense of smell is the subject of exciting  new research, a logical effort given the fact that loss of the sense of smell has been tied to loss of cognition.  A recent study published  in the Journal of Neurology further documented that  a declining sense of smell may be an early sign of cognitive problems developing.  https://n.neurology.org/content/early/2023/07/26/WNL.0000000000207659

https://www.frontiersin.org/articles/10.3389/fnins.2023.1200448/full

Physiologically, the olfactory system is the only sensory system that has direct projections to the limbic system of the brain which is crucial for memory and emotion (Haberly and Price, 1977). This direct  access to the brain’s learning and memory systems may allow treatment targeting the olfactory system, to prevent or reverse the deterioration of these systems and the deterioration of cognition in older adults via direct neural activation.

Loss of olfactory ability and the deterioration of cognition

It has been shown that as people age, the deterioration of their olfactory ability occurs before the deterioration of their cognitive abilities (Doty et al., 1984; Schaie et al., 2004).  The COVID-19 epidemic uncovered the phenomenon of the loss of the ability to smell as a consequence in some individuals, and this has been tied to long-term diminishment of cognitive abilities.  (Meng et al., 2020; Graham et al., 2021).  In one study comparisons of brain MRI scans of people who have had  Covid-19 infections had neural tissue deterioration in the regions of the brain that provide olfactory system function. (Douaud et al., 2022).

Olfactory loss precedes or accompanies cognitive decline in dementia and Brain MRI studies have shown a loss of gray matter in the hippocampus region of the brain accompanying this cognitive impairment. It seems that this association occurs not only in Alzheimer’s disease (Franks et al., 2015; Chen et al., 2021) but with a number of other nervous system conditions that cause cognitive impairment. These include Parkinson’s disease (Ponsen et al., 2004; Meusel et al., 2010), Lewy body dementia (Ross et al., 2006), frontotemporal dementia,  (Luzzi et al., 2007), Creutzfeldt-Jakob disease (Tabaton et al., 2004), and alcoholism (Rupp et al., 2003).

Olfactory stimulation restores olfactory function

Olfactory enrichment stimulation is being shown to improve olfactory abilities in those who have cognitive  dysfunction from a wide variety of conditions, including head trauma (Huang et al., 2021), Parkinson’s (Haehner et al., 2013), or aging (Zambom-Ferraresi et al., 2021). These results were achieved with daily exposure to odorants, and it was shown that further improvements can be accomplished with continuing the exposures over a longer period of time (Altundag et al., 2015; Konstantinidis et al., 2016). Increased concentration of the odorants (Damm et al., 2014), and an increased number of odorants utilized also enhances the therapeutic benefit. Mahmut et al., 2020).

Olfactory enrichment changes human brain anatomy

Brain MRI analyses have shown  that olfactory enrichment can induce beneficial changes in the brain’s anatomy. One study  Han et al. (2021)  used olfactory enrichment with 4 odorants presented  twice/day for seven months . The study subjects showed improvement in odor identification skills and larger cortical gray matter volume.

Sommelier students are exposed to different odorants on a daily basis and tasked with identifying them. Brain MRIs were performed at the beginning and at the end of the sommeliers’ 18-month of training (Filiz et al., 2022), and what resulted was an  increase in  olfactory bulb volume.

A variety of studies have documented olfactory enrichment improving  cognition in people.

Haehner et al. (2013) showed that patients with Parkinson’s disease improved their verbal fluency after olfactory enrichment. Birte-Antina et al. (2018) showed a significant improvement in verbal function, and decreased depression symptoms. Oleszkiewicz et al. (2021) exposed 68 older adults either to 9 odorants twice a day  for 3–6 months, and found the enriched olfactory experience produced improvements in cognitive abilities, dementia status, and olfactory function.

Increased complexity of olfactory enrichment remarkably improves dementia

Cha et al. (2022) exposed older adults with moderate dementia either to 40 odorants twice a day for 15 days or to no olfactory enrichment. The olfactory-enriched group showed highly significant improvements in memory, olfactory identification, depression symptoms, attention, verbal fluidity, and language skills relative to controls.

 Olfactory enrichment at night. This study sought to determine whether older adults retain or improve their cognitive ability over a six-month period after daily olfactory enrichment at night. The study showed that compared to the control group, enriched participants improved in their performance a word list recall, a key test memory. Cha et al. (2022).

Even minimal olfactory enrichment, delivered at night using an odorant diffuser improves cognition and neural function in those duals living with dementia.

Specifically which odors are therapeutic?

There are a variety of Aromatherapy scents that have been postulated  to help cognition.

Peppermint, tea tree, lemon, sweet orange, eucalyptus, orange, chamomile, lavender, clary sage, and  rosemary are among the scents that have been most widely recommended.

In a recent study utilized 43 participants, ages 60–85, who were in good general health and found to have normal cognitive abilities at the start of the study. The study subjects were divided into two groups. One group of 20 participants were exposed nightly to the scents of a variety of essential oils.  https://www.frontiersin.org/articles/10.3389/fnins.2023.1200448/full

The odorant  diffuser rotated through seven different scents one for each day of the week.

All participants underwent a series of assessments before and after the 6-month study period:

• assessment of cognitive ability
• assessment of depression /  quality of life depression
• tests of olfactory performance
• MRI  magnetic resonance imaging to assess changes in brain structure function