Frequently asked questions (FAQ)
For questions not addressed here, contact NACC (email@example.com).
How should I deal with variables that have changed across versions of the UDS?
Please refer to the Researchers Data Dictionary for the UDS as your first and primary source of information on the UDS.
What can I do if my project requires data that NACC doesn't have but that individual
ADCs do have?
Requesting external data — NACC consultants work with investigators to determine whether their requests for external data are feasible and if so, to create a list of data or specimens available at each Center. Next, NACC consultants will help the investigator draft a memo for the investigator to send to the Clinical Core Leaders or other appropriate people at the Centers of interest. All communication to Centers should clearly state that the request is not a NACC initiative and that Center participation is entirely voluntary. It is also important to note that NACC has a system of creating STUDYIDs to prevent the linking of NACC IDs to Center-assigned patient IDs, an IRB violation.
What kind of analytic support does NACC provide?
NACC routinely provides advice and guidance about the availability and interpretation of data in NACC data sets. A scientific liaison at NACC is assigned to each project. Through this liaison, investigators can seek advice about analysis and interpretation as the project proceeds. Data analysis for most projects, however, occurs at the investigator's home institution. On request, NACC can also provide statistical and methodological consultation.
By mutual consent and subject to staff time constraints, NACC scientists can take on a larger role, including hands-on data analysis, direct collaboration, and co-authorship. Those arrangements are made on a project-by-project basis and are normally initiated by the investigator.
For more information, please see Processing Your Request.
Are item-level neuropsychological test data available?
For most tests in the UDS Neuropsychological Battery, only the total score is captured. In UDS v2 Initial and Follow-up Visits, and in a subset of UDS v3 Follow-up Visits, subscale scores were recorded for the Mini-Mental State Examination (MMSE). In UDS v3 Initial Visits and a subset of Follow-up Visits, item-level data are being collected for the Montreal Cognitive Assessment (MoCA). For further details, see Form C1 (used in both UDS v2 and UDS v3) and Form C2 (used only in UDS v3 ). See also the Resarchers Data Dictionary for the UDS.
Many ADCs do retain item-level neuropsychological test results, and access to the item-level data can be sought as an external data request, as described above (see the first question, on requesting external data, at the top of this page).
Where can I find the UDS Neuropsychological Test Battery results (means, standard
deviations, etc.) for normal, MCI, and demented subjects?
For the neuropsychological test battery used in UDS v1 and UDS v2, a publication by Weintraub and colleagues [Weintraub 2009] (PDF) provides descriptive information from initial neuropsychological data of more than 3,000 cognitively normal older adults. Linear regression models were developed to estimate the impact of age, sex, and education on test performance.
The report by Weintraub et al. was not intended as a normative study. However, by combining the initial results of Weintraub and colleagues with additional statistical information obtained from the study's authors (for example, root mean square errors for model variables), Shirk et al. have sought to create a useful regression-based norms calculator that provides estimated z-scores while taking into consideration the individual's sex, education level, and/or age. This straightforward tool is available on the web for clinical research use at the NIA Alzheimer's Disease Program sites. In addition, Shirk et al. aimed to provide an easy and accessible method for calculating norms that other researchers and clinicians can apply to their own unique, site-specific data sets.
For the neuropsychological battery used in UDS v3, nothing analogous has yet been published; however, a list of useful references is available, and a UDS3 neuropsych norms calculator has been created.
Where can I find more information about the UDS3 neuropsychological battery Crosswalk Study?
More information is available here.
Is APOE genotype available?
Yes. APOE data are available for approximately 70 percent of UDS subjects. These values may be requested by investigators through a data request.
Are neuroimaging data available?
Yes. Research structural MRIs (DICOM format) are available on a subset of UDS subjects. A sample of images is available for immediate download from the MRI query system, and MRIs for analysis or publication purposes are available through a NACC data request. Data requests may also be made for volume calculations, which are available for a subset of subjects with MRIs. For more information about the data available, please see this page and the Researcher's Data Dictionary for Imaging Data.
Are biomarker data available?
Yes, NACC has CSF data for a small number of UDS subjects. Please see the Data Element Dictionary for CSF Data to see which values are reported. Apart from CSF data, other biomarkers for Alzheimer’s and other neurodegenerative diseases are not available at this time. Requests for access to specimens or external data at the ADCs may be completed as described above (see the first question, on requesting external data, at the top of this page).