The Efficacy of Modified Olfactory Training for MCI High-Risk Individuals

Mild Cognitive Impairment (MCI) represents an intermediary stage between normal aging and dementia, with a significant proportion of cases progressing to dementia. No simple and effective therapeutic strategies are available to halt or reverse this progression. Olfactory dysfunction, a common early clinical manifestation of neurodegenerative diseases such as Alzheimer's Disease (AD), often precedes cognitive decline. Subjective Cognitive Decline (SCD) is increasingly recognized as a prodromal stage of MCI and dementia, which, together with olfactory dysfunction, provides a critical window for early intervention.

Conventional olfactory training (COT) has been shown to improve olfactory function, cognitive abilities, and brain connectivity in healthy elderly individuals, suggesting its potential to enhance neuroplasticity. Preliminary studies indicate that modified olfactory training (MOT) may yield superior outcomes compared to COT, with higher rates of olfactory recovery and improved deposition in the olfactory fissure. However, the efficacy of MOT in delaying or preventing the progression of olfactory dysfunction to MCI remains unclear.

In this study, the investigators planned to recruit 114 patients and divided them into three groups for control group and olfactory training with conventional and modified devices, and validate the effectiveness of the modified device based on changes in cognitive function and the comparison of the outcomes of the three groups.

Inclusion criteria

• Age and Gender: Individuals aged 60-80 years, regardless of gender.
• Diagnosis of Idiopathic Olfactory Dysfunction: overall TDI score below 30.75 points using the Sniffin' Sticks test. Without olfactory impairment due to traumatic, sinusitis-related, congenital, toxic/drug-induced causes, post-operative conditions, tumors, or post-upper respiratory infections.
• Diagnosis of Subjective Cognitive Decline: Montreal Cognitive Assessment (MoCA) score >24 for middle school level and above, >19 for elementary school level, and >13 for illiterate individuals. Amyloid β (Aβ) deposition in the brain (defined as Aβ42 < 550 ∼ 813 pg/ml)， the higher Formula of Hulstaert (defined as [(Aβ42/(240 + 1.18 × tau) ≤1]）, and hippocampus atrophy.
• Consent: Willingness to sign an informed consent form.

Exclusion criteria

• Comorbid Chronic Diseases or Severe Concurrent Illnesses: Individuals with conditions such as hypertension, diabetes, bronchopneumonia, malignant tumors， or chronic obstructive pulmonary disease.

• Recent Medication Use: Exclusion of participants who have taken corticosteroids, antimicrobials, leukotriene antagonists, or antihistamines within the last four weeks.

• Inability to Comply with Study Requirements: Based on the researcher's judgment, individuals who are unable to tolerate olfactory function tests and treatment， complete the study or comply with its requirements due to memory or behavioral abnormalities, depression, severe alcohol consumption, or previous non-compliance.