About NACC data
Longitudinal data: The UDS
From 2005 to the present, ADRCs have been contributing data to the Uniform Data Set (UDS), using a prospective, standardized, and longitudinal clinical evaluation of the subjects in the National Institute on Aging's ADRC Program. In each participant's annual UDS visit, 16 data-collection forms are completed by the clinician, covering topics from subject demographics, to neurological examination findings, to diagnosis.
The UDS has been expanded with two modules, completed by ADRCs on a voluntary basis, that collect additional, diagnosis-specific information:
- The FTLD Module, collected 2012 – present
- The LBD Module, collected 2017 – present
The UDS study population
- The UDS reflects the total enrollment of the NIA’s Alzheimer’s Disease Research Centers (ADRCs) since 2005 and includes participants with cognitive status ranging from normal cognition, to MCI, and demented.
- Each Center enrolls its participants according to its own protocol — e.g., clinician referral, self-referral by participants or family members, active recruitment in the community organizations, etc. Most Centers also enroll volunteers with normal cognition, and these tend to be highly educated.
- NACC subjects are not a statistically based sample of the U.S. population — with or without dementia. Rather, they are best regarded as a referral-based or volunteer case series. Therefore, NACC data do not lend themselves to estimates of the prevalence or incidence of dementia subtypes in the general U.S. population.
- Some ADRCs require that participants agree to autopsy before being accepted for UDS participation; this may impose further selection pressures on the makeup of the NACC sample.
- Written informed consent is obtained from all participants and co-participants.
How UDS data are collected
- The UDS data are collected using a standardized evaluation of participants enrolled in ADRC clinics. Data are recorded directly on UDS forms (hard copy or electronic) during the evaluation process.
- Information is collected during in-person office visits, home visits, and telephone calls. In addition, Milestone Forms are used to document participant death and drop-out.
- The UDS is longitudinal, and its protocol requires approximately annual follow-up for as long as the participant is able to be involved. Late-stage participants forced to drop out due to health may continue to be followed strictly for autopsy purposes.
- Data are collected by trained clinicians and clinic personnel from participants and their co-participants (usually a close friend or family member).
- Depending on a given ADRC’s protocol, diagnosis is made by either a consensus team or a single physician (the one who conducted the examination).
- Although the focus of the ADRCs is Alzheimer's disease, the Centers also collect data on a variety of associated disorders, such as vascular dementia, Lewy body dementia, and frontotemporal lobar degeneration.
- The NACC Handbook, a more detailed look at the database
- Data summary tables, providing a look at the participant numbers by demographics and diagnosis
- Additional data sets, with links to related data sets of interest
Autopsy data: The Neuropathology Data Set
The Neuropathology Data Set (NP) contains autopsy data for a subset of both MDS and UDS participants and Minimum Data Set (MDS) subjects (see below). Please note that changes in diagnostic criteria and staining methods may limit the available data for certain analyses.
Cross-sectional data: The Minimum Data Set
Beginning in 1984 and ending with the 2005 implementation of the UDS, brief, single-record descriptions of ADRC subjects were collected retrospectively to form the Minimum Data Set (MDS). Because of the lack of detailed, longitudinal, and standardized clinical data in the MDS, the utility of the MDS for research is limited, and combining the clinical data in the MDS with the UDS is generally not recommended.
More data at NACC: Imaging and fluid biomarker data
Imaging data: MRI and PET
Magnetic resonance imaging, along with volumetric summary measures, are available for a subset of participants in the Uniform Data Set. NACC’s MRIs are most appropriately described as a convenience sample of images, voluntarily submitted by several Alzheimer's Disease Research Centers. Imaging data collection and acquisition protocols vary by ADRC; thus, packages of MRI files at NACC may include T1-weighted, FLAIR, DTI, T2, or other MR series (and any combination thereof), and subjects may or may not have multiple scan sessions in the NACC database.
- For an estimate of the number of available scans that meet your image-type and subject criteria, use NACC’s MRI Preview System.
- To acquire images and volume data, submit a data request. Both DICOM and NIfTI formats are available. MRIs archived by subject ID and MRI date (.zip), delivered via a cloud-based distribution system and linked to any requested UDS, FTLD, or NP data.
|Image acquisition period||2005 – present|
|Subjects||ADRC subjects enrolled in the Uniform Data Set (UDS)|
|Clinical diagnoses||Normal cognition, MCI, dementia|
|Linked genotype data||Available from ADGC and NIAGADS|
|Longitudinal MRIs||Available for some subjects|
NACC is also acquiring amyloid PET images and making them available as DICOM files via data request.
For some UDS subjects, CSF values are available for Abeta, P-tau, and T-tau. Please note that CSF assay methods are not standardized across the ADRCs, and that some subjects may have CSF values from multiple dates.
From NACC and partners: Genotypic and genomic data
Genotypic data (i.e., APOE status) is available at NACC for 75 percent of UDS participants, as well as information on whether the partipant or their family has any known AD or FTLD mutations. It can be requested as part of a custom data request, and it is also included in the Quick Access Full Data File. In addition, genomic data can be requested from NACC partner organizations. Researchers who are affiliated with an ADRC can request genomic data on that Center's own participants directly from the ADGC. The genomic data held at NIAGADS, however, is available to all qualified researchers.