About NACC Data
The UDS: Longitudinal Neurocognitive and Clinical Phenotypic Data
Since 2005, Alzheimer’s Disease Research Centers (ADRCs) have been contributing data to the Uniform Data Set (UDS), using a prospective, standardized, and longitudinal clinical evaluation of the participants in the National Institute on Aging’s ADRC Program. In each participant’s annual UDS visit, 18 data-collection forms are completed by the clinician, covering topics from participant demographics to neurological examination findings, to diagnosis. All NACC data is freely available to researchers. To receive the National Alzheimer’s Coordinating Center (NACC) data, submit a Quick-Access file request.
The UDS study population
The UDS reflects the total enrollment of the ADRC Program since 2005 and includes participants with cognitive status ranging from no cognitive impairment to dementia.
Each Center enrolls its participants according to its own protocol — e.g., clinician referral, self-referral by participants or family members, active recruitment in community organizations, etc. Most Centers also enroll volunteers with normal cognition, and these participants tend to be highly educated.
NACC participants 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.
ADRCs collect written informed consent from all participants and co-participants.
How UDS data are collected
The UDS data are collected using a standardized protocol for all participants enrolled in ADRC clinical cores. Data are recorded directly on UDS forms (hard copy or electronic) during the evaluation process, by clinicians or clinical staff and then processed by ADRC data cores before submission to NACC.
Information is collected during in-person UDS related office visits, home visits, and video/telephone calls. In addition, Milestone Forms are used to document participant change in residence and living situation as well as reported death or decline to participate or administrative discontinuation by the ADRC.
The UDS is longitudinal, and its protocol requires annual follow-up (within a +/- 6-month window) for as long as the participant is able and willing to be involved. Visit dates are important and used to calculate protocol compliance, beginning with the date of the first visit. Late-stage participants forced to drop out due to health may continue to be followed strictly for autopsy purposes (as noted on the Milestone form) where no further UDS visit is expected, without loss of protocol.
Data are collected by trained clinicians and clinic personnel from direct observation and/or examination of participants and their co-participants (usually a close friend or family member).
Depending on a given ADRC’s practice, assigned UDS diagnosis is made by either a consensus panel or a single physician (usually the clinician who conducted the neurological examination).
Although the focus of the ADRCs is generally Alzheimer’s disease (AD), each ADRC also enrolls persons with other neurologic conditions or with no neurological or cognitive issues at all. This is done consistent with the individual theme of each ADRC and is consistent with the understanding of Alzheimer’s disease and related dementias (AD/ADRD) as well as the current understanding that single etiology dementias rarely occur and it is much more common to individuals to have co-existent combinations of AD, Lewy Body Disease (LBD), vascular disease, TDP-43 and other factors.
More detail
The NACC Handbook — a more detailed look at the database for researchers
Data summary tables — participant numbers by demographics and diagnosis
Additional data sets — related external data sets of interest
Population and Disease-Specific Data
Modules
The UDS has three condition-specific modules. These are voluntarily completed by ADRCs, to document specific diseases or syndromes. The modules are completed at the choice of the ADRC, usually when the result of the main UDS indicates an additional predominant diagnosis or syndrome. Module data are held separately but linked by NACCID to UDS and other data captured by NACC.
The Frontotemporal Lobar Degeneration (FTLD) Module has been collected since 2012 and is available to researchers via the NACC Quick-Access File. The Module is aimed at evaluating those suffering from or at risk for any of the forms of frontotemporal lobar degeneration and includes controls. To receive the FTLD Module data in the NACC Quick-Access file, submit a data request.
The Lewy Body Disease (LBD) Module has been collected since 2017 and is available to researchers via the NACC Quick-Access File. The shortened version of the LBD Module (v3.1) was implemented in 2020. The Module evaluates those with clinically determined Lewy Body syndrome and includes controls. To receive the LBD Module data in the NACC Quick-Access file, submit a data request.
The Down Syndrome Module was implemented in 2020 and was designed to be used with a subset of UDS participants; specifically, adults with Down syndrome. Due to trisomy 21, adults with Down syndrome have an increased risk for early onset of Alzheimer’s disease. Centers have begun collecting data which will be made available via the NACC Quick-Access File within the next year.
Stand-alone forms
The COVID Impact Survey F2/F3 v2 aims to collect valuable information about COVID vaccinations, infections, and hospitalizations of the UDS participants. Collecting this valuable data will be important in understanding the impact of COVID in the AD community. These forms can be administered outside of a UDS visit but can be linked to UDS data via NACCID. The data from version 1 of the forms is only distributed upon special request; all data, including version 2 form data, will be included as part of the NACC Quick-Access file within the next year.
The Linguistic History Form (CLS) is used to collect additional information on UDS participants who indicate they are of Hispanic/Latino ethnicity on the UDS demographics form. It can be administered any time and is linked to UDS data. The data is only distributed upon special request and is not currently part of the NACC Quick-Access file.
Minimum Data Set (MDS)Beginning in 1984 and ending with the 2005 implementation of the UDS, brief, single-record descriptions of ADRC participants were collected retrospectively to form the Minimum Data Set (MDS). They were abstracted from ADRC enrollment records, primarily by data managers, research assistants, and others at each ADRC. The MDS data are cross-sectional and were not originally recorded following a standard protocol. They were merely abstracted from ADRC records which primarily followed local definitions. 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. For this reason, it is not currently part of the NACC Quick-Access file but is available upon special request.
Autopsy data: The Neuropathology Data Set and Brief Data Set
The Neuropathology Data Set (NP) is collected using a standardized neuropathological evaluation and contains autopsy data for a subset of both UDS and MDS participants. The standard data set collection began in 2002. Neuropathologists were asked to retrospectively complete the forms from their internal reports for the period of 1984 – 2002 and then to proceed prospectively 2002 to present. Starting in 2005 when the UDS began, the NP data can be linked to detailed longitudinal clinical data. Please note that changes in diagnostic criteria and staining methods may limit the available data for certain analyses. To receive the NP data in the NACC Quick-Access file, submit a data request.
The Brief Data Set (BDS), initiated circa 2021, is used to capture a brief set of clinical data for the purpose of submitting a neuropathology data form. This form is required if a participant did not have any UDS visit data or MDS data at NACC prior to autopsy. BDS data will be included as part of the NACC Quick-Access file within the next year.
Imaging
The SCAN initiative: Standardized MRI and PET data
What is SCAN data?
The goal of SCAN is to promote standardization of PET and MR image acquisition so that images can be combined across multiple Alzheimer's Disease Researcher Centers (ADRCs). ADRCs acquire and upload SCAN-compliant images to a portal hosted by the Laboratory of Neuro Imaging (LONI) at the University of Southern California where they are de-identified and defaced by the Aging and Dementia Imaging Research (ADIR) laboratory at Mayo Clinic. The PET and MRI laboratories at the University of Michigan and the Aging and Dementia Research (ADIR) Laboratory at Mayo Clinic then process for quality assurance and harmonization. Following this, the PET laboratory at UC Berkeley and the MRI laboratories at Mayo Clinic and UC Davis analyze the images to produce analysis results such as brain volumes, cortical thickness, surface area, and Standardized Uptake Value Ratio (SUVR) data. The SCAN initiative is a collaboration between NACC, UC Berkeley, Mayo Clinic, University of Michigan, UC Davis, and the Laboratory of Neuro Imaging (LONI), funded by the National Institute on Aging.
What SCAN data is available at NACC?
Submit a data request to receive the SCAN Quick-Access files including:
- MRI and PET analysis results such as brain volumes, cortical thickness, surface area, and SUVRs.
- MRI and PET numerical data such as summary and quality control (QC) information.
- Request access to defaced MR and PET images, available through LONI.
Mixed protocol (non-standard) MRI and PET data
What is Mixed Protocol MRI and PET data?
NACC collects and shares MRI and/or PET data that does not adhere to the SCAN/CLARiTI protocols or was collected prior to January 2021. This data has previously been labeled 'non-SCAN compliant', 'heterogeneous' or 'legacy' MRI and PET data. We have partnered with imaging experts such as Dr. DeCarli at the University of California at Davis, Dr. Beth Mormino at Stanford, and Dr. Tim Hohman at Vanderbilt University to clean, label, and produce harmonized analysis results for mixed protocol MRI and PET data that has been submitted to NACC.
Imaging data collection and acquisition protocols vary by ADRC; thus, packages of mixed protocol files at NACC may include:
- For MRI: T1-weighted, FLAIR, DTI, T2, or other MR series (and any combination thereof).
- For PET: Tau and amyloid scans (or a combination).
- For both MRI and PET: participants may or may not have multiple scan sessions in the NACC database.
What data is available at NACC?
Submit a data request to receive the NACC Quick-Access files including:
- Images, along with volumetric summary measures, are available for a subset of participants in the Uniform Data Set. Both DICOM and NIFTI formats are available
- Amyloid Positron emission tomography (PET) scans and (coming soon!) tau PET scan and Standard Uptake Value Ratios (SUVRs), are available for a subset of participants in the Uniform Data Set.
Images are archived by NACCID and study or scan date (.zip), delivered via a cloud-based distribution system, and linked to any requested UDS, FTLD, or NP data.
Additional Imaging Resources
For an estimate of the number of available mixed protocol scans that meet your image-type and participant criteria, use NACC’s MRI Preview System.
Real-time SCAN Public Dashboard: See how much SCAN-compliant PET and MRI data from across the ADRC Program has passed QC and is available for analysis.
Mixed Protocol amyloid PET scans are also available via data request for a small number of participants.
Fluid biomarker data
CSF data
For a limited number of UDS participants, cerebrospinal fluid (CSF) biomarker values are available for Aβ, P-tau, and T-tau. Note that the same CSF values can vary by assay method (ELISA, Luminex, etc.) and Center. Centers use different lab assay kits, and ranges for amyloid beta and tau are scaled differently for each brand of kit and have different range and cut off values for positivity. Thus, the values cannot be directly combined in analysis; instead, they will require additional harmonization (not done at NACC currently). To acquire CSF data via the NACC Quick-Access file, submit a data request.
Other fluid biomarker data
Blood based biomarker data will be available in the coming year in cooperation with the National Centralized Repository for Alzheimer’s Disease (NCRAD). For more information, please see this page.
The NACC Quick-Access File indicates which ADRC participants have fluid biomarker and other biospecimen data available to researchers via NCRAD.
Coming soon
Additional blood biomarker metadata and analysis data for NfL, GFAP, Aβ 42/40, P-tau 181, and other high-impact blood biomarkers prioritized by the ADRC Blood Biomarker Steering Committee.
Genetic and Genomic data
APOE genotype is obtained from NCRAD and coded as part of the NACC database for most UDS participants. In addition, genomic array and sequence data (GWAS, WES/WGS) can be requested from The National Institute on Aging Genetics of Alzheimer’s Disease Data Storage Site (NIAGADS) where it is indexed by NACCID. Researchers who are affiliated with an ADRC can request genomic data on that Center’s own participants directly from the Alzheimer’s Disease Genetics Consortium (ADGC) collection. The genomic data held at NIAGADS, however, are available to all qualified researchers.
The NACC Quick-Access File indicates which ADRC participants have genetic and genomic data available to researchers via NIAGADS and ADGC.
Pilot data streams that are under development
NACC is building a new modern Data Portal (DP), powered by Flywheel, that supports multimodal integration of old and new data streams, including the following list of new data modalities. All data and metadata for a given ADRC participant will be assigned a unique global identifier called a NACCID, enabling a comprehensive and integrated inventory of all ADRC participant data.
EHR/CMS
The NACC DP system will be built to handle a range of data collection workflows including tabular data such as real-world Electronic Health Records (EHR), Observational Medical Outcomes Partnership (OMOP), or other clinical data such as Centers for Medicare & Medicaid (CMS) claims data.
Digital biomarker data
The NACC DP will also digitally integrate ADRC participant fluid biospecimen (i.e., blood and cerebral spinal fluid) metadata and analysis data housed at NCRAD. The biospecimens are analyzed to detect biomarkers of disease which can be interrogated with multi-omic data from the AD Knowledge Portal to discover new biomarkers. New biomarkers that could be used for early diagnosis and/or as targets for disease modifying drugs in the future.
Digital neuropathology data
Metadata and analysis data related to brain autopsy tissue will be available through the NACC DP and integrated across all participant data. NACC plans to incorporate digital neuropathology data from the Brain Digital Slide Archive (BDSA) and the CLARiTI initiative. The goal is to standardize the method of analysis, collection, and formatting of this data so it is comparable across all data sources.
Multi-omics from the AD Knowledge Portal — NACC will integrate multi-omics metadata variables for ADRC participants from Mayo P30 Multi-Omics Core and Alzheimer’s Gut Microbiome Project (AGMP) within the NACC DP. The metadata will be developed by Sage Bionetworks. NACC will collaborate with Sage to build an interface (potentially an API) to update data availability between Sage and the NACC data platform. The metadata that NACC ingests from Sage will be connected to NACCIDs and all other multimodal data streams available via the NACC Data Platform. NACC will also work with Sage to establish metadata flow from NACC to the Sage AD Knowledge Portal. Our goal will be to enable researchers searching for data within the AD Knowledge Portal to see what types of data are available within the NACC Data Platform for participants of interest. Researchers visiting the AD Knowledge Portal will be able to determine whether the following data types are available within the NACC Data Platform: UDS, neuropathology, heterogeneous MRI/PET, standard MRI/PET (SCAN), NCRAD (Yes/no data initially and then top 5 blood biomarkers starting in 2024), Biomarker (CSF), NIAGADS (Yes/no for GWAS and sequencing data; GWAS and sequencing can be requested using NACC IDs), and modules (LBD, FTLD, Down Syndrome).