This is a longitudinal observational study recruiting individuals between the ages of 50 and 90 with different types of dementia as well as a comparison group without cognitive deficits. Participants are/will be recruited at sites across Canada and will undergo assessments, neuroimaging, and biological sample collection.

This is a longitudinal observational study that started in Phase I with the recruitment of 1173 participants between the ages of 50 and 90 years with Subjective Cognitive Impairment, Mild Cognitive Impairment, Mild Cognitive Impairment with subcortical vascular lesions, Alzheimer's Disease, Mixed dementia, Lewy Body Dementia, Parkinson's Disease Dementia, Parkinson's Disease with Mild Cognitive Impairment and Frontotemporal Dementia as well as healthy elderly subjects without cognitive complaints or deficits. These participants were enrolled in 30 different centres across Canada.

All subjects involved in the study underwent rigorous evaluations at baseline, including clinical assessment, neuropsychological assessment, genomics and neuroimaging. Biological samples from blood, saliva, urine, fecal matter, buccal cells and cerebrospinal fluid were collected, stored, and analyzed.

Longitudinal follow-up determining if there has been any change in their diagnosis was carried out annually and longitudinal re-evaluation was carried out at two times: Time 2 and Time 3.

In Time 3, 400 participants across the non-dementia cohorts (Cognitively Unimpaired, Subjective Cognitive Impairment, Mild Cognitive Impairment, Mild Cognitive Impairment with a Vascular Component, Parkinson's Disease with no Cognitive Impairment, Parkinson's Disease with Mild Cognitive Impairment) with up to 12 years of education will be recruited.

Inclusion Criteria:

• Has subjective or objective cognitive impairment
• Written informed consent must be obtained and documented (from the patient or, where jurisdictions allow it, from a caregiver/family member)
• Sufficient proficiency in English or French to undertake self report and neuropsychological testing
• Geographic accessibility to the study site
• Must have a study partner who can participate as required in the protocol (provide corroborative information)
• Up to 12 years of education
• Fits into one of the following groups: Cognitively Unimpaired, Subjective Cognitive Impairment, Mild Cognitive Impairment, Vascular Mild Cognitive Impairment, Parkinson's Disease, Parkinson's Disease with Mild Cognitive Impairment

Exclusion Criteria:

• The presence of other significant known chronic brain disease such as: moderate to severe chronic static leukoencephalopathy (including previous traumatic injury), multiple sclerosis, a serious developmental handicap, malignant tumors, Parkinson's disease (other than for the Parkinson's cohort), and other rarer brain illnesses
• Ongoing alcohol or drug abuse which in the opinion of the investigator may interfere with the subject's ability to comply with the study procedures
• Symptomatic stroke within the previous year
• Unable to undergo MRI scan due to medical contraindications or inability to tolerate the procedure

2300 English and/or French-speaking participants recruited from across Canada in the following groups:

• 650 Cognitively healthy volunteers
• 300 volunteers with Subjective Cognitive Decline
• 400 volunteers with Mild Cognitive Impairment
• 200 volunteers with Vascular Mild Cognitive Impairment
• 150 volunteers with Alzheimer's disease
• 200 volunteers with Dementia of Mixed Etiology
• 200 volunteers with Parkinson's disease and cognitive impairment
• 200 volunteers with Frontotemporal spectrum dementia

Data will be shared initially with all Canadian Consortium on Neurodegeneration and Aging (CCNA) affiliated researchers and eventually with all interested researchers internationally.

The data is currently available.

Reaserchers who which to access the database will be required to create an account through CCNA and demonstrate their research credentials and their affiliation to a recognized research organization. Users must confirm that their intended use of data respects CCNA policies and applicable ethical, legal, and data governance requirements. Researchers are further required to hold data secure, not to attempt the re-identification of research participants, and not to perform research that could cause communities to experience stigmatization or discrimination.