Effect of intensive olfactory training for cognitive function in patients with dementia

Abstract

Recent evidence has revealed an association between neurodegenerative disorders and olfactory dysfunction. However, whether olfactory training can improve cognitive impairment in patients with dementia requires further study. The present study aimed to resolve this by developing an intensive olfactory training (IOT) protocol and assessing its impact on each of the cognitive domains in patients with dementia.Methods: Patients were prospectively recruited between June 2020 and September 2020. Baseline evaluations included demographic data, olfactory function test, depression scale and detailed cognitive function tests. Thirty-four patients in the experimental group underwent IOT twice a day with a 40-odor set for 15 days, while 31 individuals in the control group received conservative management. Follow-up evaluations using the depression scale and detailed cognitive function tests were performed after IOT.Results: Baseline characteristics were not different between the two groups. The IOT group showed significant improvements in depression, attention, memory and language functions, but not global cognition, frontal executive, or visuospatial functions compared with the control group. Conclusion:This study shows the ability of IOT to alleviate depression and improve some cognitive functions in patients with dementia. These results suggest that IOT may be an effective non-pharmacological approach for improving the symptoms of dementia. Geriatr Gerontol Int 2022; 22: 5-11.

Does Olfactory Training Improve Brain Function and Cognition? A Systematic Review

“…After 3 months, the odorants were changed to 5 new odorants • Randomized to either: 1) Standard OT (sniff each odorant for 30 s 2x/day) or 2) Intense OT (sniff each odorant for 30 s 4x/day) • The duration of the training ranged from 108 to 340 days ( M days = 64.3) • Participants were tested before and after OT with an interview, Sniffin’ Sticks test and cognitive tests (i.e., MoCA, COWAT, & Verbal Semantic Fluency Task) • 2-group pre-post-experimental design (over 108–304 days; M days = 208.6) Primary Outcome • To determine whether intensity of OT leads to better outcomes in both olfactory and cognitive domains • The standard OT group improved more on odor detection threshold score than the intense OT group • Increased olfactory sensitivity was significantly related to increased odor discrimination and odor identification • Verbal fluency was significantly improved for the standard OT group but not for the intense OT group • Olfactory sensitivity was significantly correlated with MoCA scores • Improved MoCA scores were negatively correlated with the duration of OT Strengths • Confounds of smoking, eating, drinking, and strong perfumes were controlled • Cognition was assessed • Long duration of OT with new odorants introduced midway • Normosmic group received OT Limitations • No active control group • Small N • OT adherence was not reported • Brain imaging was not included • Standard group had lower baseline TDI • Unequal distribution of etiologies 4. Cha et al ( 2022 ) Effect of Intensive Olfactory Training for Cognitive Function in Patients with Dementia Adults with Dementia (N = 65) • Intensive OT Group: n = 34 ( M age = 85 yrs) • Control Group: n = 31 ( M age = 85 yrs) Entry Criteria • > / = 65 yrs old • Dementia dx • MMSE ≥ 10 • Lack of sinus/nasal disease • The Intensive OT group received 2x/day OT consisting of 40 odorants smelled for 5 s each over 15 days • Olfaction was assessed using the YSK olfactory function (YOF) test • Cognition was assessed with 9 tests • 2-group pre-post experimental design (over 15 days) • Control group was not administered OT Primary Outcome • Measure the effect of IOT on the cognitive functions of dementia patients • The Intensive OT group demonstrated statistically significant improvements of cognitive function in attention, memory, and language • The Intensive OT group had significantly improved depression testing scores Strengths • Researchers’ administration of the OT likely resulted in greater OT delivery/adherence for the intensive OT group • Administered 40 odorants Limitations • OT only limited duration • Small sample size • Lack of long-term follow-up • Lack of differentiation among types of dementia …”

“…Oleszkie-wicz et al ( 2021 ) N = 68 (3 TX groups) • Healthy Older Adults • Simple OT Group • Mixture OT Group • Control Group • 9 odorants of each type • 2x/day ~ 12–24 wks • Diary • Data reported Change not reported + Simple Group No Change No Change ↑MoCA In simple group Not measured 4. Cha et al ( 2022 ) N = 65 (2 TX groups) • Intense OT group ( n = 34) • No OT Control Group ( n = 31) • 40 odorants • 2x/day @ 5 s for each odor • 15 days • Diary not used • ≤ 20% adherence to treatment constituted dropout Not Reported Not measured Not measured Not Measured ↑attention, memory, and language in OT group Not measured Neuroimaging Studies 5. Kollndorfer et al ( 2014 ) N = 7 (1 TX group) • Adults w/ Anosmia • 4 odorants from a selection of 6 odorants • 12 wks @ 2x/day • Diary • Data reported No Change + No Change No Change Not measured • OT reduced widespread activation of odor processing, showing network reorganization 6.…”

“…Cognition was assessed in five of the studies with limited sample sizes ranging from 33–91 participants, and with a limited cognitive battery, except for Cha et al ( 2022 ) which had nine cognitive tests. Across all five studies, there is convergent findings that indicate OT in adults with and without olfactory loss at baseline can cognitively benefit from OT; albeit, for Chen et al ( 2022 ), these results were mixed as the control group also experienced some cognitive improvements.…”

Olfactory loss is a predisposing factor for depression, while olfactory enrichment is an effective treatment for depression

“…The olfactory-enriched group had a significant improvement of olfactory function, improved verbal function, and decreased depression symptoms. Cha et al (2022) exposed 34 older adults with dementia (but with a Mini-Mental State Examination score of at least 10) to 40 odorants twice a day for 15 days. The control group consisted of 31 individuals with dementia that received no such stimulation; there were no initial differences between groups.…”

Intensive olfactory training and emotional memory in patients with dementia

“…Int. 1 Currently, findings on the effect of olfactory training on cognitive function are inconsistent. While some studies report that olfactory training improves cognitive function, [2][3][4][5] others have reported no such effects.…”