Introduction
The DIAN-Observational Study (DIAN-O) is the longitudinal observational arm of the [Dominantly Inherited Alzheimer Network (DIAN)](/entities/dian-study), an international research consortium dedicated to studying individuals with autosomal dominant Alzheimer's disease (AD). DIAN-O is designed to characterize the preclinical and prodromal stages of Alzheimer's disease in individuals who carry pathogenic mutations in [APP](/entities/app-protein), [PSEN1](/proteins/psen1-protein), or [PSEN2](/entities/psen2) genes.
Study Overview
DIAN-O represents the foundational observational component of the DIAN initiative, established to understand the precise sequence of biomarker changes that occur decades before the onset of clinical symptoms in autosomal dominant Alzheimer's disease (ADAD). Unlike therapeutic intervention trials (DIAN-TX), DIAN-O focuses exclusively on natural disease progression and biomarker evolution.
Key Characteristics
- Study Type: Prospective longitudinal observational cohort
- Enrollment Period: 2008 – present
- Participant Population: Mutation carriers and non-carriers from families with autosomal dominant AD
- Follow-up Interval: Every 2 years (annual for selected assessments)
- Global Sites: 14+ research centers across North America, Europe, Australia, and Asia
Study Design
Participant Cohorts
DIAN-O enrolls three distinct participant groups:
...Introduction
The DIAN-Observational Study (DIAN-O) is the longitudinal observational arm of the [Dominantly Inherited Alzheimer Network (DIAN)](/entities/dian-study), an international research consortium dedicated to studying individuals with autosomal dominant Alzheimer's disease (AD). DIAN-O is designed to characterize the preclinical and prodromal stages of Alzheimer's disease in individuals who carry pathogenic mutations in [APP](/entities/app-protein), [PSEN1](/proteins/psen1-protein), or [PSEN2](/entities/psen2) genes.
Study Overview
DIAN-O represents the foundational observational component of the DIAN initiative, established to understand the precise sequence of biomarker changes that occur decades before the onset of clinical symptoms in autosomal dominant Alzheimer's disease (ADAD). Unlike therapeutic intervention trials (DIAN-TX), DIAN-O focuses exclusively on natural disease progression and biomarker evolution.
Key Characteristics
- Study Type: Prospective longitudinal observational cohort
- Enrollment Period: 2008 – present
- Participant Population: Mutation carriers and non-carriers from families with autosomal dominant AD
- Follow-up Interval: Every 2 years (annual for selected assessments)
- Global Sites: 14+ research centers across North America, Europe, Australia, and Asia
Study Design
Participant Cohorts
DIAN-O enrolls three distinct participant groups:
Mutation Carriers (MC): Individuals who carry pathogenic mutations in [APP](/entities/app-protein), [PSEN1](/proteins/psen1-protein), or [PSEN2](/entities/psen2) — genes known to cause early-onset autosomal dominant Alzheimer's disease
Non-Carriers (NC): siblings or family members who do not carry the familial mutation, serving as cognitively healthy control subjects
At-Risk Individuals: Pre-symptomatic mutation carriers identified through comprehensive family screening programsAssessment Schedule
Participants in DIAN-O undergo comprehensive assessments at regular intervals:
| Assessment Category | Frequency | Key Measurements |
|---------------------|-----------|------------------|
| Cognitive Testing | Annual | Neuropsychological batteries, clinical dementia rating |
| Brain Imaging | Every 2 years | MRI, amyloid PET, [tau](/proteins/tau) PET, FDG-PET |
| Cerebrospinal Fluid | Every 2 years | [Aβ40](/proteins/amyloid-beta), Aβ42, total tau, phosphorylated tau |
| Blood Biomarkers | Annual | Plasma Aβ, tau, [neurofilament light](/biomarkers/neurofilament-light-chain-nfl) chain (NfL) |
| Clinical Assessment | Annual | AD symptoms, functional abilities, neuropsychiatric symptoms |
Primary Objectives
1. Characterize Preclinical AD
DIAN-O aims to identify and characterize the earliest biomarker changes that occur in individuals with autosomal dominant Alzheimer's disease before any clinical symptoms appear. This includes:
- Detecting subtle cognitive changes using sensitive neuropsychological measures
- Identifying amyloid deposition via amyloid PET imaging
- Measuring cerebrospinal fluid Aβ42 and tau levels
- Characterizing brain structural changes using MRI
2. Establish Biomarker Timeline
A central goal of DIAN-O is to create a precise timeline of pathological changes in autosomal dominant AD:
Mermaid diagram (expand to render)
This timeline enables prediction of symptom onset and provides a framework for timing therapeutic interventions.
3. Identify Disease Modifiers
DIAN-O collects extensive genetic, environmental, and lifestyle data to identify factors that may modify disease progression, including:
- [APOE](/proteins/apoe) genotype effects on age of onset
- Cognitive reserve and educational attainment
- Vascular risk factors
- Lifestyle modifications
Key Findings
Estimated Year of Onset (EYO)
DIAN-O researchers developed the "Estimated Year of Onset" (EYO) metric, which calculates the approximate number of years before or after the expected age of symptom onset based on the participant's parental mutation. EYO has become a standard approach for analyzing biomarker trajectories in preclinical AD.
Biomarker Classification
DIAN-O established a classification scheme for preclinical AD based on biomarker status:
- Stage 0: Normal amyloid, normal tau
- Stage 1: Abnormal amyloid, normal tau
- Stage 2: Abnormal amyloid, abnormal tau
- Stage 3: Abnormal amyloid, abnormal tau, subtle cognitive changes
Critical Findings Published
Amyloid Cascade in ADAD: DIAN-O data confirmed that amyloid deposition begins approximately 20 years before expected symptom onset, validating the amyloid cascade hypothesis in the dominantly inherited form of AD[@bateman2012]
Tau Spreading: Tau pathology spreads in a predictable pattern from the [entorhinal cortex](/brain-regions/entorhinal-cortex) to other cortical regions, following a staging system that correlates with clinical progression[@gordon2016]
Cognitive Reserve: Higher education and cognitive reserve appear to delay clinical onset despite similar biomarker burden[@morenasrodriguez2019]
Treatment Timing: Data from DIAN-O informed the design of DIAN-TX trials, suggesting that intervention may need to occur at least 10-15 years before expected symptom onset[@fleisher2015]Relationship to DIAN-TX
DIAN-O serves as the foundational observational study that informs the DIAN-TX therapeutic trials. Participants who complete DIAN-O assessments are eligible for enrollment in DIAN-TX intervention studies. The observational data helps:
- Identify optimal treatment windows
- Select appropriate outcome measures
- Determine sample size requirements
- Characterize natural disease progression for comparison
Participating Institutions
DIAN-O is conducted at leading research institutions globally, including:
- Washington University School of Medicine (St. Louis, MO — coordinating center)
- University of Melbourne (Australia)
- University of Toronto (Canada)
- University College London (UK)
- Massachusetts General Hospital (Boston, MA)
- University of Pittsburgh (PA)
Data Access
DIAN-O data is available to qualified researchers through the DIAN Distributed Archives and the NIAAA Data Archive. Researchers can request access to:
- Raw imaging data (MRI, PET)
- Cerebrospinal fluid biomarker data
- Genetic data
- Longitudinal cognitive assessments
See Also
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Parkinson's Disease](/diseases/parkinsons-disease)
External Links
- [PubMed](https://pubmed.ncbi.nlm.nih.gov/)
- [Allen Human Brain Atlas](https://brain-map.org/)
- [KEGG Pathways](https://www.genome.jp/kegg/pathway.html)
References
[Bateman et al., Clinical and biomarker changes in dominantly inherited Alzheimer's disease (2012) (2012)](https://doi.org/10.1056/NEJMoa1202753)
[Gordon et al., Tau and amyloid imaging and CSF biomarkers in autosomal dominant AD (2016) (2016)](https://doi.org/10.1016/j.jalz.2016.01.003)
[Morenas-Rodriguez et al., Cognitive reserve and age of onset in autosomal dominant AD (2019) (2019)](https://doi.org/10.1016/j.jalz.2019.02.007)
[Fleisher et al., Designing DIAN-TX trials (2015) (2015)](https://doi.org/10.1016/j.jalz.2015.01.005)
Unknown, Dominantly Inherited Alzheimer Network - Official Website (n.d.)