I want to let everybody know that I got the title of this post "Olfactory enrichment improves olfactory ability in humans with olfactory loss due to Parkinson’s" from section 1.4 of the main document this thread is discussing: Overnight olfactory enrichment using an odorant diffuser improves memory and modifies the uncinate fasciculus in older adultsfrontiersin.org/journals/ne...
I titled the post with the heading for section 1.4, and then I added the word "Parkinson's" to the end of the title because within section 1.4, Parkinson's is listed as one of the causes of olfactory loss that can be addressed with olfactory stimulation:
"1.4. Olfactory stimulation restores olfactory function
Olfactory enrichment improves olfactory ability in humans with olfactory loss due to post-infection olfactory dysfunction (Konstantinidis et al., 2013, 2016; Damm et al., 2014; Geißler et al., 2014), 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 four odorants that represented the resinous, flowery, fruity, and aromatic odor groups. There are further improvements in olfactory ability with increased duration of exposure (Altundag et al., 2015; Konstantinidis et al., 2016), increased concentration of the odorants (Damm et al., 2014), and an increased number of odorants (Mahmut et al., 2020)."
I am point this out because I dug into the 2013 study section 1.4 is referencing. Olfactory Training in Patients with Parkinson’s Disease 2013 sci-hub.ru/10.1371/journal....
That study is not that impressive. It is positive, but not super compelling. Here is my summary of the study:
2013 study with 70 PD patients with olfactory loss smelled 4 odors (Rose, Eucalyptus, Lemon, and Cloves) for 10 seconds each in the morning and at night for 12 weeks. 20% of training group had increased olfactory function and 6% of the training group had decreased olfactory function. 9% of the control group had increased olfactory function and 11% of the control group had decreased olfactory function.
I am still full steam ahead with olfactory training.
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MBAnderson posted this 6 months ago but I wanted to nutshell it.
Marc's post: Too bad we've lost our sense of smell healthunlocked.com/cure-par... and the study he linked to: Overnight olfactory enrichment using an odorant diffuser improves memory and modifies the uncinate fasciculus in older adults frontiersin.org/journals/ne...
Nutshell Methods:
Participants used an odorant diffuser and 7 essential oil odorants: Rose, Orange, Eucalyptus, Lemon, Peppermint, Rosemary, and Lavender.
They turned on the diffuser when they went to bed, and a timer on the diffuser released the odorant into the air for 2 hours when they first went to sleep.
They rotated through the different odorants each night.
Individuals were exposed to 7 different odorants a week, one per night, for 2 h, using an odorant diffuser.
A statistically significant 226% improvement was observed in the enriched group compared to the control group on the Rey Auditory Verbal Learning Test and improved functioning was observed in the left uncinate fasciculus, as assessed by mean diffusivity.
Conclusion: Minimal olfactory enrichment administered at night produces improvements in both cognitive and neural functioning. Thus, olfactory enrichment may provide an effective and low-effort pathway to improved brain health.
Olfactory enrichment improves olfactory ability in humans with olfactory loss due to post-infection olfactory dysfunction (Konstantinidis et al., 2013, 2016; Damm et al., 2014; Geißler et al., 2014), 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 four odorants that represented the resinous, flowery, fruity, and aromatic odor groups. There are further improvements in olfactory ability with increased duration of exposure (Altundag et al., 2015; Konstantinidis et al., 2016), increased concentration of the odorants (Damm et al., 2014), and an increased number of odorants (Mahmut et al., 2020).
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One extraordinary correlation that I have noticed consistently is when I am on optimal dose, my olfactory senses are heightened and I have the best days ever. I am never ON when I don't smell a thing.
Marc! I pulled my head out and figured something out. If it was a snake it would have bit me.
I will dig into tomorrow (it's late) but:
I don't think it makes a difference which diffuser you use. I doubt that it makes a difference which specific odorants you use. Like I said, I will dig into this tomorrow and write up a detailed post.
Just to let you know where I am coming from, check out these four sections from the paper you shared. There were at least 10 successful Olfactory Enrichment studies before this latest study. All of them used slightly different methods and they all had some level of success. Anyway, more on this tomorrow:
1.1. Olfactory enrichment alone improves brain and behavior in laboratory animals
Olfactory enrichment involves the daily exposure of individuals to multiple odorants and Veyrac et al. (2009) showed that olfactory enrichment alone could improve both memory and neurogenesis in the mouse brain. They further showed that novelty was the critical element in this kind of stimulation, as exposure to odorant mixtures did not produce these changes, while exposure to multiple odorants individually did. Rusznák et al. (2018) also showed that exposure to various essential oils alone for 30 min/day over 3 months induced neurogenesis in both the olfactory bulb and the hippocampus.
The olfactory system is the only sensory system that has direct projections to the limbic system which is crucial for memory and emotion, and which is the most relevant for this investigation (Haberly and Price, 1977), while the other sensory systems have indirect connections to this region via the thalamus. This unique access to the brain’s learning and memory systems may allow the olfactory system to prevent or reverse the deterioration of these systems via direct neural activation.
1.4. Olfactory stimulation restores olfactory function
Olfactory enrichment improves olfactory ability in humans with olfactory loss due to post-infection olfactory dysfunction (Konstantinidis et al., 2013, 2016; Damm et al., 2014; Geißler et al., 2014), 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 four odorants that represented the resinous, flowery, fruity, and aromatic odor groups. There are further improvements in olfactory ability with increased duration of exposure (Altundag et al., 2015; Konstantinidis et al., 2016), increased concentration of the odorants (Damm et al., 2014), and an increased number of odorants (Mahmut et al., 2020).
1.5. Olfactory enrichment changes human brain anatomy
Al Aïn et al. (2019) found that olfactory enrichment improved odor identification compared to that of visually enriched controls. Moreover, MRI analysis showed that olfactory enrichment led to increased cortical thickness in the right inferior frontal gyrus, the bilateral fusiform gyrus and the entorhinal cortex when compared to controls. Gellrich et al. (2017) found that olfactory enrichment given to people with olfactory deficiencies increased gray matter volume in the hippocampus and the thalamus, but no the brain regions. Similarly, Han et al. (2021) gave older adults olfactory enrichment for 7 months using 4 odorants twice/day, and patients had improved odor identification skills and larger cortical gray matter volume relative to controls. Sommelier students are exposed to dozens of novel odorants each day of their training. Using a longitudinal design, the brains of sommelier students were imaged with MRI at the start and end of their 18-month training and were compared with control students (Filiz et al., 2022). Olfactory enrichment of sommelier students increased olfactory bulb volume and it also increased the thickness of the entorhinal cortex. There were no significant changes in control group brains.
1.6. Olfactory enrichment improves cognition in humans
Haehner et al. (2013) showed that patients with Parkinson’s disease improved their verbal fluency after olfactory enrichment. Birte-Antina et al. (2018) provided olfactory enrichment for adults with 4 essential-oil odorants twice a day for 5 months. Controls solved daily Sudoku puzzles during that time. The olfactory-enriched group had a significant improvement of olfactory function, improved verbal function, and decreased depression symptoms. Oleszkiewicz et al. (2021) exposed 68 older adults either to 9 odorants twice a day or to no new olfactory stimulation for 3–6 months, and found the enriched olfactory experience produced improvements in cognitive abilities, dementia status, and olfactory function, relative to the control condition. Specifically, the Montreal Cognitive Assessment revealed a significant difference between the olfactory-enriched group and controls. They also found that the AD8 Dementia Screening Interview showed that olfactory-enriched participants had no increase in dementia symptoms over the course of the trial, while control participants had such an increase. Finally, an improvement on olfactory sensitivity was seen in olfactory-enriched individuals, but not controls. At the same time, Chen et al. (2022) did not find memory improvement in older adults with mild cognitive impairment after brief exposures to multiple odorants twice each day for 4 months. They did find that olfactory-enriched individuals increased frontal lobe activation but had no change in gray matter volume. In a similar study, Haehner et al. (2022) found that improvements in olfactory discrimination, increased thickness of the hippocampus, and improved global cognition were associated with increased thickness of the hippocampus, entorhinal cortex, and medial temporal lobes. Moreover, the change in the thickness of entorhinal cortex was positively associated with improvement of executive function.
So... I am going through all the references in that paper Marc posted. I am just going to add random notes here on the references:
Bitter, T., Gudziol, H., Burmeister, H. P., Mentzel, H.-J., Guntinas-Lichius, O., and Gaser, C. (2010b). Anosmia leads to a loss of gray matter in cortical brain areas. Chem. Senses 35, 407–415. doi: 10.1093/chemse/bjq028 sci-hub.ru/10.1093/chemse/b...
"In summary, many neurological diseases, especially neurodegenerative diseases like AD and PD, are accompanied with olfactory impairments. This raises the question if the decrease of gray brain matter of the MPC and NAc is part of the neurological disease per se or sign of the concomitant olfactory deficit. We postulate that the olfactory deficit contributes significantly to the, in the literature described, volumetric changes in these diseases. Another possible interpretation is that the cortical atrophy leads itself to the olfactory impairment. To prove this hypothesis, further studies in these patient collectives must be performed to show if there is such a correlation between GM reduction and olfactory impairment."
So maybe the loss of sense of smell is itself leading to loss of brain volume?
As a side-note, I find that, if I can't fall back to sleep during the night, a few drops of lavender oil on my pillow are a delightful diversion and seem usually to help me get back to sleep,
STEM-Talk Episode 164: Michael Leon on olfactory stimulation as a buffer for dementia symptoms ihmc.us/stemtalk/episode-164/
What if the path to delaying the onset of dementia symptoms begins at the nose?
It is a doorway that the research of Dr. Michael Leon opened with a 2023 study on the power of olfaction enrichment to influence memory function and brain health. The findings drew wide acclaim and interest when his results found that stimulation of our sense of smell with essential oils had a profound impact on memory, cognition, and language recall.
Our conversation with Leon on STEM-Talk Episode 164 is available now wherever you enjoy podcasts.
Leon’s long research career has focused on the influence of environmental enrichment on neurological function, disease, and disorders. He has studied the benefits of sensory-motor stimulation for children with autism spectrum disorder, for the treatment of anorexia and for those with dementia and neurological conditions.
He is a professor emeritus in the Department of Neurobiology and Behavior at the University of California Irvine, where his Leon Lab has focused on studying the benefits of increased sensory-motor activity in children with autism spectrum disorder.
The work that the Leon Lab is doing is fascinating, and the applications this olfaction stimulation study are potentially important and wide-reaching.
This is the diffuser used in the "Smell training improves olfactory function and alters brain structure" study: $158 DIFFUSER WORLD : Aroma-Ace Essential Oil Atomizing Diffuser
I got this one. Simple. Seems to work. $59: Aromatherapy Diffuser - Professional Essential Oil Diffuser, Spray Technology, Full Spectrum Oil Adaptability, Anhydrous, No Heat, Super Quiet, Portable, Battery Powered (Black Silver) amazon.com/dp/B0BQYBQCJ1?re...
Participants used an odorant diffuser and 7 essential oil odorants: Rose, Orange, Eucalyptus, Lemon, Peppermint, Rosemary, and Lavender.
I got Lemon, Eucalyptus, and Lemon at Meijer in 15 ML bottles. I got Lavender, Rosemary, Rose, and Orange at Amazon, but I got them in 4 oz bottles that don't fit my diffuser, so now I need to find some empty 15 ml bottles or find Lavender, Rosemary, Rose, and Orange locally in 10 or 15 ml bottles. I do have Tangerine in a 15 ml bottle, so that might be close enough to Orange.
I can find everything except Rose in 15 ml bottles at my local Walmart!
Very interesting thread to read. HWP noticed when he first started B1 therapy that his sense of smell is coming back. I have several friends who are big fans of and sell Young Living Essential Oils. Can't hurt to try.
So I am digging into the underlying studies. This is the most on point: Olfactory Training in Patients with Parkinson’s Disease 2013sci-hub.ru/10.1371/journal....
Summary
2013 study with 70 PD patients with olfactory loss smelled 4 odors (Rose, Eucalyptus, Lemon, and Cloves) for 10 seconds each in the morning and at night for 12 weeks. 20% of training group had increased olfactory function and 6% of the training group had decreased olfactory function. 9% of the control group had increased olfactory function and 11% of the control group had decreased olfactory function.
Participants
70 subjects with PD and olfactory loss and were on stable anti-parkinsonian medication for at least 4 weeks prior to study enrollment and during the study. Exclusion criteria: Identifiable cause of Parkinsonism or signs for atypical Parkinsonian disorders, dementia, and psychiatric conditions interfering with study participation.
35 patients were assigned to the olfactory training group and 35 subjects to the control group (no training).
Methods
Olfactory training was performed over a period of 12 weeks while patients exposed themselves twice daily to four odors (phenyl ethyl alcohol: rose, eucalyptol: eucalyptus, citronellal: lemon, and eugenol: cloves). Patients were asked to sniff the odors in the morning and in the evening for approximately 10 seconds each. Basically, patients opened jars and smelled them for 10 seconds.
Olfactory testing was performed before and after training using the ‘‘Sniffin’ Sticks’’ (thresholds for phenyl ethyl alcohol, tests for odor discrimination, and odor identification) in addition to threshold tests for the odors used in the training process.
Odors
Rose, Eucalyptus, Lemon, and Cloves.
Equipment
Training patients received four brown glass jars (total volume 50 mL) with one of the four odors in each (1 mL each, soaked in cotton pads to prevent spilling). All jars were labeled with the odor name.
Results
A) olfactory training produces both an improved sensitivity towards the odors used in the training process and an overall increase of olfactory function. It appears to increase olfactory function in 20% of the subjects over a period of 12 weeks compared to 9% of subjects who had no olfactory training.
(B) Olfactory training proves to be useful independently from age, sex, duration and severity of the disease, and severity of olfactory dysfunction.
(C) The training effect appears to be more pronounced in patients with tremor dominant type of PD.
Notes
Odor discrimination, but not odor threshold, improved in response to olfactory training.
Tremor dominant PD patients had the greatest benefit from training.
The 4 odorants were chosen to be representative of four odor categories claimed by Henning in his work on the ‘‘odor prism’’, where he tried to identify primary odors. These categories are flowery: rose, foul fruity: lemon, aromatic: cloves, burnt and resinous: eucalyptus.
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