The Uniform Data Set (longitudinal follow-up)
The Uniform Data Set (UDS) is the primary data set used by researchers interested in clinical data. The NIA/NIH Alzheimer's Disease Research Centers (ADRCs) began submitting UDS data to NACC in September 2005, using the UDS Forms to collect standardized clinical data from subjects who are evaluated on an approximately annual basis. Since 2005, the UDS forms have undergone two major revisions to reflect advances in the science and incorporate new diagnostic criteria. To combine data across the three versions, a Researcher’s Data Dictionary (RDD) was created. This document, the RDD-UDS, should be the first and primary resource for researchers analyzing NACC clinical and demographic data.
As a resource for investigators in their analysis, NACC has provided a CSV file of all RDD-UDS variables and coding.
For more information, please see the section below titled "Advice on research design and best variables to use."
FTLD Module (frontotemporal lobar degeneration)
Beginning in February 2012, a subset of UDS subjects have also been evaluated using the supplemental FTLD Module. At Centers participating in this voluntary effort, subjects with suspected FTLD and/or controls are evaluated with the FTLD Module in addition to the standard UDS Forms.
LBD Module (Lewy body disease)
Beginning in August 2017, a subset of UDS subjects have also been evaluated using the supplemental LBD Module . At Centers participating in this voluntary effort, subjects with suspected LBD and/or controls are evaluated with the LBD Module in addition to the standard UDS Forms. These data will be made available for research once sufficient numbers of participants and visits have accumulated.
Researcher’s Data Dictionary: Neuropathology Data Set (autopsy data)
The NP data set comprises subjects who have died and consented to autopsy. The NP data-collection form has undergone numerous revisions to reflect advances in the science and incorporate new diagnostic criteria. To combine data across versions, a Researcher’s Data Dictionary (RDD) was created. The RDD-NP should be the first and primary resource for researchers analyzing NACC neuropathology data.
As a resource for investigators in their analysis, NACC has provided a CSV file of all RDD-NP variables and coding.
Imaging available for download
A subset of UDS subjects have one or more MRIs available to download as zip files (a subset because MRI submission is voluntary on the part of the Centers). Research structural MRIs are stored in DICOM and NIfTI format and a variety of scan types (primarily T1, T2, FLAIR, and DTI). A very small subset of UDS subjects also have one or more amyloid PET scans available to download. Please note that PET scans are only available from a small number of Centers.
Researcher’s Data Dictionary: Biomarker and Imaging Data Sets
Three data dictionaries have been created to aid investigators in the analysis of NACC’s biomarker and imaging data sets. See below for a description of each of these data sets and their corresponding data dictionaries.
Imaging data (MRI calculated volumes)
Among the UDS subjects with MRI files stored at NACC, a subset have standardized calculated volume values (e.g., hippocampal volume). These data are provided to NACC by the IDeA lab at the University of California, Davis. Investigators requesting these data should review the description of the calculation methods and protocols. The Researcher’s Data Dictionary — Imaging Data (RDD-ID) includes MRI calculated volume variables, as well as variables associated with the DICOM and NIfTI files stored at NACC.
Calculation Methods — Hippocampal segmentation
Hippocampal segmentation is based on a multi-atlas propagation method 1 with label refinement from intensity-based tissue classification. Atlas labels were acquired from the newly developed EADC-ADNI hippocampal harmonization protocol 2, 3.
- Carmichael OT, Aizenstein HA, Davis SW, et al. Atlas-based hippocampus segmentation in Alzheimer's disease and mild cognitive impairment. Neuroimage 2005; 27:979-990.
- Boccardi M, Bocchetta M, Apostolova LG, et al. Delphi definition of the EADC-ADNI Harmonized Protocol for hippocampal segmentation on magnetic resonance. Alzheimers Dement 2014.
- Bocchetta M, Boccardi M, Ganzola R, et al. Harmonized benchmark labels of the hippocampus on magnetic resonance: The EADC-ADNI project. Alzheimers Dement 2014.
ADNI protocol — Four tissue segmentation in ADNI II
CSF biomarker data (CSF Aβ, total Tau, p-Tau)
For a small sample of UDS subjects, NACC stores CSF biomarker values from a single lumbar puncture or longitudinal lumbar punctures. The Data Element Dictionary — CSF (DED-CSF) describes the variables related to CSF biomarker data. Please note that these data come from a small number of Centers.
Genetic data (APOE genotype, availability of genetic data)
APOE genotype data are available for a large subset of UDS subjects. The Researcher’s Data Dictionary — Genetic Data (RDD-Gen) describes variables relating to APOE genotype data as well as variables indicating the availability of genetic data at the Alzheimer’s Disease Genetics Consortium (ADGC) and the NIA Genetics of Alzheimer’s Disease Data Storage Site (NIAGADS).
As a resource for investigators in their analysis, NACC has provided a CSV file of all RDD-Gen variables and coding.
Minimum Data Set (MDS) (abstracted records)
Before the UDS was implemented at Centers in 2005, data on Center subjects were collected retrospectively via data abstraction and were included in the MDS. Because of the limited scope of the MDS and its retrospective and cross-sectional nature, NACC recommends using data from the UDS rather than the MDS for most research proposals.