The goal of this study is to learn more about the changes in the brains of patients with cognitive impairment (MCI) and Alzheimer's Disease (AD).

The main questions the study aims to answer are:

1. What findings can be used to earlier detect patients that will develop Alzheimers?
2. Which differences are seen between healthy and cognitively impaired patients?
3. Which differences are seen between patients with Alzheimers disease?

Participants will undergo:

• Cognitive tests
• Magnetic resonance imaging (MRI)
• Electroencephalography (EEG)
• Blood sample collection
• Fecal sample collection
• A randomized group will undergo polysomnography analysis.

The projects aims to map brain changes in patients with mild cognitive impairment (MCI) and Alzheimer's Disease (AD) by combining different assesment modalities.

In the MRI, researchers will get the opportunity to analyse both structural and functional brain changes. In the EEG, changes in elctrical activites will be measured. The blood samples allow researchers to analyse specific dementia and inflammation proteins, while fecal speciments can be used to assess bacterial composition. Additionally, the cognitive testing allow to assess the specific part of cognitive function which is affected.

Inclusion Criteria:

• MCI and AD according to relevant ICD-criterias.
• Control cohort is age and gender matched with other cohorts.

Exclusion Criteria:

• Uneligibility for any of the planned neuroimagery devices (MRI, EEG)
• AD diagnosis before the age of 65 (Early-onset AD).
• Brain tumor
• Traumtic head injury
• Earlier neurosurgery
• Other neyrodegenerative diseases (i.e Parkinson and ALS)
• Diseases related to inflammation and auto-immunity (i.e MS)

The study population is from Tronderlag in Norway, mainly in and around Trondheim city.