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

BACKGROUND: The olfactory system is affected early in Alzheimer's disease and olfactory loss can already be observed in patients with mild cognitive impairment (MCI). Olfactory training is effective for improving olfactory and cognitive function by stimulating the olfactory pathway, but its effect on patients with MCI remains unclear. OBJECTIVE: The aim of this randomized, prospective, controlled, blinded study was to assess whether a 4-month period of olfactory training (frequent short-term sniffing various odors) may have an effect on olfactory function, cognitive function, and morphology of medial temporal lobe (MTL) subregions and olfactory bulb in MCI patients. METHODS: A total of thirty-seven MCI patients were randomly assigned to the training group or a placebo group, which were performed twice a day for 4 months. Olfactory assessments, cognitive tests and magnetic resonance imaging were performed at the baseline and follow-up period. RESULTS: After the training, there was an increase in odor discrimination, and increased cortical thickness of bilateral hippocampus (CA23DG and CA1) and mean MTL. Additionally, the change of olfactory score was positively associated with change of volume of olfactory bulb and hippocampus; the change of global cognition was positively associated with change of cortical thickness of hippocampus, entorhinal cortex and mean MTL; the change of cortical thickness of entorhinal cortex was positively associated with change of executive function. CONCLUSION: Olfactory training was associated with an increase in cortical thickness of the hippocampus but not olfactory bulb volume in patients with MCI. Olfactory training may serve as an early intervention of preventing hippocampal atrophy.

Predictors of subjective cognitive deficits in patients with mild cognitive impairment.

BACKGROUND: Detailed examination of cognitive deficits in patients with mild cognitive impairment (MCI) yields substantial diagnostic and prognostic value, specifically with respect to memory. Magnitude and characteristics of subjective cognitive deficits, however, often receive less attention in this population at risk for developing dementia. METHODS: We investigated predictors of subjective cognitive deficits in patients with MCI, using a detailed assessment for such impairments associated with different cognitive domains, as well as demographic and clinical variables including magnetic resonance imaging data. RESULTS: The strongest predictor for subjective memory deficits was depressed mood, whereas subjective performance issues associated with attention or executive functions also corresponded to measurable impairments in the respective cognitive domains. Reduced hippocampal thickness and hemispheric entorhinal cortex thickness asymmetry were associated with objective memory impairment but not with subjective deficits or symptoms of depression. CONCLUSIONS: Whereas low objective memory performance and reduced cortical thickness within medial temporal lobe subregions could be associated with neurodegeneration, greater subjective memory deficits in patients with MCI may indicate psychological burden.

The Effect of Olfactory Training on Olfaction, Cognition, and Brain Function in Patients with Mild Cognitive Impairment.

BACKGROUND: The olfactory system is affected very early in Alzheimer's disease and olfactory loss can already be observed in patients with mild cognitive impairment (MCI), an early stage of AD. OBJECTIVE: The aim of this randomized, prospective, controlled, blinded study was to evaluate whether olfactory training (OT) may have an effect on olfactory function, cognitive impairment, and brain activation in MCI patients after a 4-month period of frequent short-term exposure to various odors. METHODS: A total of 38 MCI outpatients were randomly assigned to OT or a control training condition, which were performed twice a day for 4 months. Olfactory testing, comprehensive neuropsychological assessment, and a passive odor perception task based on magnetic resonance imaging were performed before and after training. RESULTS: The results suggested that OT exhibited no significant effect on olfaction and cognitive function. Additionally, OT exhibited a positive effect on frontal lobe activation (left middle frontal gyrus and orbital-frontal cortex) but exhibited no effect on grey matter volume. Moreover, the change of olfactory scores was positively associated with the change of frontal activation. CONCLUSION: OT was found to have a limited effect on olfaction and cognition in patients with MCI compared to a non-OT condition but increased their functional response to odors in frontal area.