Establish Diagnostic Models Based on Olfactory Function and Odor-induced Brain Activation for Diabetes-Related Cognitive Impairment

A Cross-sectional and Longitudinal Study to Establish Diagnostic Models Based on Olfactory Function and Odor-induced Brain Activation for Diabetes-Related Cognitive Impairment

This is a cross-sectional and longitudinal study to establish diagnostic models based on olfactory function assessments and odor-induced brain activation for cognitive impairment in patients with type 2 diabetes mellitus.

Patients with diabetes have increased risks of cognitive impairment and dementia, which affecting the quality of life and diabetes management. Therefore, it is an urgent challenge to identify non-invasive biomarkers for early diagnosis and prognosis of the cognitive decline in patients with diabetes. Previous research has shown that both olfactory dysfunction and decreased odor-induced brain activation are present before clinically measurable cognitive decrements in type 2 diabetes. This is a cross-sectional and longitudinal study to establish diagnostic models based on olfactory function assessments and odor-induced brain activation for cognitive impairment in patients with type 2 diabetes mellitus. The investigators will recruit 200 patients with type 2 diabetes in the outpatient and inpatient departments. Health controls will be recruited from the community. At the baseline, clinical information collection, 100g-steamed bread meal test, biochemical measurement, cognitive assessments, olfactory test and functional magnetic resonance imaging(fMRI) scan will be conducted for all participants. Study duration was 3 years with a follow-up every 18 months. In the longitudinal study, all of the assessments will be repeated to evaluate changes of observational parameters.

Inclusion Criteria:

• Aged 40-75 years
• Right handedness
• Possessed over 6-year education
• Provision of informed consent prior to any study specific procedures
• Disease duration of T2DM patients >1 year

Exclusion Criteria:

• Control participants would be excluded if they had a fasting blood glucose level >7.0 mmol/L; glucose level> 7.8 mmol/L after oral glucose tolerance test (OGTT); HbA1c>5.7%
• Control participants would be excluded if they had a Montreal Cognitive Assessment (MoCA, Beijing edition) score of < 26
• Any acute disease
• History of neurologic or psychological illness
• Abnormal results of thyroid hormones, vitamin B12, and folate
• Metal implants, unable to complete the MR scanning
• Partial or complete olfactory dysfunction associated with sinusitis, allergic rhinitis, and deviated nasal septum
• Pregnant or lactating women
• Participating in other clinical trials at the same time or within 6 months prior to the start of the trial