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 subject’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.
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.