Training with Odors Impacts Hippocampal Thickness in Patients with Mild Cognitive Impairment

Haehner, Antje; Chen, Ben; Espin, Melanie; Haußmann, Robert; Matthes, Claudia; Desser, Dmitriy; Loessner, Lorenz; Brandt, Moritz; Donix, Markus; Hummel, Thomas

doi:10.3233/jad-220248

Cited by 8 publications

(5 citation statements)

References 58 publications

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“…Olfactory training was found to improve cognitive functioning in patients with dementia [42]. Moreover, olfactory training had a positive effect on frontal lobe activation in response to odors and increased the cortical thickness of the hippocampus [43,44]. Even though the data are still limited at this time, these findings warrant further research on olfaction in AD.…”

Section: Discussionmentioning

confidence: 96%

Odor Discrimination as a Marker of Early Alzheimer’s Disease

Audronytė

Pakulaite-Kazliene

Sutnikiene

et al. 2023

JAD

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Background: Olfactory dysfunction is an early symptom of Alzheimer’s disease (AD). However, olfactory tests are rarely performed in clinical practice because their diagnostic efficacy in detecting early AD is unclear. Objective: To investigate odor discrimination in patients with early AD and the efficacy of olfactory discrimination tests in differentiating these patients from subjects with normal cognition (CN). Methods: Thirty patients each with mild dementia due to AD (MD-AD) and mild cognitive impairment due to AD (MCI-AD) and 30 older subjects with CN were enrolled. All participants underwent cognitive examinations (CDR, MMSE, ADAS-Cog 13, and verbal fluency) and odor discrimination tests (Sniffin’ Sticks test, Burghart®, Germany). Results: The MD-AD group achieved significantly worse scores on the olfactory discrimination test than the MCI-AD group, and the MCI-AD group achieved significantly worse results than the CN group (p < 0.05). A cut-off score of≤10 had a diagnostic accuracy of 94.44% (95% CI, 87.51–98.17%) in differentiating patients with MCI-AD/MD-AD from subjects with CN and of 91.67% (95% CI, 81.61–97.24%) in differentiating those with MCI-AD from subjects with CN. Our multinomial logistic regression model with demographic data and ADAS-Cog 13 scores as predictor variables correctly classified 82.2% of the cases (CN, 93.3%; MC-AD, 70%; MD-AD, 83.3%); on adding the olfactory discrimination score to the model, the percentage increased to 92.2% (CN, 96.7%; MCI-AD, 86.7%; MD-AD, 93.3%). Conclusion: Odor discrimination is impaired in cases of early AD and continues to deteriorate as the disease progresses. The olfactory discrimination test showed good diagnostic efficacy in detecting early AD.

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Section: Discussionmentioning

confidence: 96%

Odor Discrimination as a Marker of Early Alzheimer’s Disease

Audronytė

Pakulaite-Kazliene

Sutnikiene

et al. 2023

JAD

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“…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.…”

Section: Introductionmentioning

confidence: 82%

Overnight olfactory enrichment using an odorant diffuser improves memory and modifies the uncinate fasciculus in older adults

et al. 2023

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ObjectiveCognitive loss in older adults is a growing issue in our society, and there is a need to develop inexpensive, simple, effective in-home treatments. This study was conducted to explore the use of olfactory enrichment at night to improve cognitive ability in healthy older adults.MethodsMale and female older adults (N = 43), age 60–85, were enrolled in the study and randomly assigned to an Olfactory Enriched or Control group. Individuals in the enriched group were exposed to 7 different odorants a week, one per night, for 2 h, using an odorant diffuser. Individuals in the control group had the same experience with de minimis amounts of odorant. Neuropsychological assessments and fMRI scans were administered at the beginning of the study and after 6 months.ResultsA 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.ConclusionMinimal 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.

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“…In addition, structural changes have been evaluated with neuroimaging tests in patients with MCI during olfactory training, showing an increase in the cortical thickness of the hippocampus as improved smell discrimination, without significant alterations in the dimensions of the olfactory bulb. Therefore, this intervention has been suggested to prevent hippocampal atrophy in these cases [ 58 ].…”

Section: Discussionmentioning

confidence: 99%

The Value of Subjective Olfactometry as a Predictive Biomarker of Neurodegenerative Diseases: A Systematic Review

Ramos-Casademont,

Martin-Jimenez,

Villarreal-Garza

et al. 2024

Life

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Background: Olfactory disorders (ODs) are reported to be an early non-motor sign before the onset of deterioration in neurodegenerative diseases (NDs) such as Alzheimer’s and Parkinson’s. This systematic revision aims to review the current literature and the value of subjective olfactometry (SO) in the early diagnosis of cognitive decline and NDs. Methods: A systematic literature review was conducted following the PRISMA framework. Four different authors reviewed six different databases. The main variables analyzed were olfactory function and cognitive status. The quality of results was evaluated using the Oxford Centre of Evidence-based Medicine Levels. Results: Twenty-one cross-sectional and cohort studies and six meta-analyses were included. Most of them found an association between ODs and NDs. A prevalence of ODs greater than 80% was shown in Parkinson’s disease, proportional to the severity of symptoms. In Alzheimer’s, ODs were associated with early diagnosis and prognosis. All SO tests employed in the literature showed enough predictive value to correlate with early stages of cognitive decline. Conclusions: SO should be considered a pivotal tool when diagnosing NDs due to their association with early symptoms and prognosis. However, in the current literature, no firm consensus exists on the optimal SO tests and protocols that should be applied to the study of NDs, which prevents the interpretability and comparability of results among studies.

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Training with Odors Impacts Hippocampal Thickness in Patients with Mild Cognitive Impairment

Cited by 8 publications

References 58 publications

Odor Discrimination as a Marker of Early Alzheimer’s Disease

Odor Discrimination as a Marker of Early Alzheimer’s Disease

Overnight olfactory enrichment using an odorant diffuser improves memory and modifies the uncinate fasciculus in older adults

The Value of Subjective Olfactometry as a Predictive Biomarker of Neurodegenerative Diseases: A Systematic Review

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