The goal of this observational cross-sectional study is to explore the characteristics of language, speech, and motor function in persons with Mild Cognitive Impairment due to Alzheimer's disease ("MCI due to AD") and persons with mild and moderate Alzheimer's disease ("AD"). This study aims to:

• Explore motor, speech, and language functions in MCI due to AD and mild and moderate AD.
• Combine the characteristics of motor, language, and speech functions to gain more insight into the association of language, speech, and motor changes during MCI due to AD and mild and moderate AD.

Researchers will compare the outcomes to an age-matched control group without cognitive impairment.

Participants will undergo:

• Two motor function tests to assess gait and hand grip strength.
• Four language and speech function tests to assess spontaneous speech and verbal fluency..

Inclusion Criteria:

A subject with MCI with a likelihood of underlying AD pathophysiology must meet the following criteria:

• Established diagnosis of MCI due to AD with a likelihood according to NIA-AA criteria (Albert et al., 2011).
• A score of stage three on the Global Deterioration Scale (GDS) (Reisberg et al., 1982).

A subject with AD must meet the following criteria:

• Established diagnosis of AD (amnestic or non-amnestic) or etiologically mixed presentation of AD according to DSM-5 (American Psychiatric Association, 2013) or NINCDS-ARDRA criteria (Jack et al., 2018; McKann et al., 2011).
• The following scores on the Global Deterioration Scale (GDS): four for mild AD, five for moderate AD (Reisberg et al., 1982).

All subjects of the control group must meet the following criteria:

• A score of stage one or two on the Global Deterioration Scale (GDS) (Reisberg et al., 1982).
• They are age-matched with the MCI due to AD or AD patients included in the study.

All subjects must meet the following criteria:

• First language is Dutch and/or Frisian.
• Able to walk independently with or without walking aid.
• Able to squeeze with each hand.

Exclusion Criteria:

A subject with MCI due to AD or AD who meets the following criteria will be excluded from participation in this study:

• Having a neurological or neurodegenerative disease or disorder that may be contributing to cognitive impairment above and beyond that caused by AD or mixed AD; Down's syndrome, other subtypes of dementia, autism spectrum disorder.
• Having an established diagnosis of a psychiatric disorder, e.g. schizophrenia, depression.

All subjects in the control group who meets following criteria will be excluded from participation in this study:

● Suffers from a neurological, neurodegenerative or psychiatric disease or disorder.

All subjects in any group who meet any of the following criteria will be excluded from participation in this study:

• Hearing loss (with or without hearing aid) that affects communication.
• Vision loss (with or without glasses or lenses) that affects communication.
• History of language problems, speech problems or dyslexia.
• Suffers from additional disorders or diseases which may limit gait, hand grip strength, language and/or speech.
• Medication use that influence gait, hand grip strength, speech or language performance at time of testing.
• Being terminally ill (i.e., life expectancy < 2 weeks according to the attending physician).

The envisaged total participants of this study is: 52 persons with MCI due to AD, 52 persons with mild AD, 52 persons with moderate AD, 52 and 52 age-matched persons without cognitive impairment. The first language of the participants is either Frisian and/or Dutch. The participants may in addition to that also speak a Dutch dialect or another language

This study is based on FAIR principles (Findable, Accessible, Interoperable and Reusable). This means that, all anonymized data and meta-data will be archived and shared during or after 5 years after completion of this study in one or more of the following database systems: Faith Research (https://www.faithresearch.nl/), DANS ('Data Archiving and Networked Services) and DataverseNL (https://dataverse.nl).