Introduction

What is ADNI?

The Alzheimer’s Disease Neuroimaging Initiative (ADNI) study is a multisite, longitudinal observational study, which aims to improve scientific understanding of Alzheimer’s disease (AD) by collecting data and sharing it with the scientific community. The primary goals of ADNI are to validate biomarkers for clinical trials and to rapidly share ADNI data with scientists via the LONI-IDA.

AD is an irreversible neurodegenerative disease that affects millions of people worldwide and results in a loss of cognitive function.

ADNI has operated continuously since 2004 and has enrolled thousands of participants. Scientific understanding of AD has evolved considerably over the course of the study, and the study itself has evolved to reflect that improved understanding.

By staying at the forefront of AD research, the ADNI study remains an invaluable resource for investigators all over the world in both academia and industry. Indeed, more than 5000 peer reviewed scientific papers have been published using ADNI data, and the data set has seen extensive use in the pharmaceutical industry.

The major challenge for potential users of the ADNI study is the effects of its complex and evolving design on the resulting data set. This dynamic nature of the study has led to a very rich but enormous and complicated multimodal/multidisciplinary data set.

ADNI is required to compete for new funding every 5-6 years. ADNI leadership decided that each new phase or version of ADNI must utilize the most up to date technology to reflect advances in the field.

For example, MRI scanners have continued to improve, and the MRI scanning sequences used in ADNI have changed over time to provide data users with better quality imaging data as the technology evolves. Therefore, the nature of the data collected in each phase of ADNI has important differences to note.

However, ADNI has also tried to maintain continuity in many aspects of data collection, allowing researchers to utilize longitudinal data from the same subjects across multiple phases of the ADNI study.

The purpose of this documentation

The goal of this document is to provide guidance to investigators who are interested in utilizing the ADNI data set. We will explain how the data are collected, stored, and organized, how the conventions and procedures of the study have changed over time, and how those changes are reflected in the available data.

This documentation is focused primarily on the tabular component of the ADNI data set. There is also a wealth of ADNI data available in non-tabular modalities, including Positron Emission Tomography (PET) and Magnetic Resonance (MR) image files, neuropathology tissue slide image files, biofluid biomarker data, and genetic data stored in specialized formats which falls largely outside the scope of this document.

In addition to this documentation, there are other sources of information available for ADNI data users to reference, namely the public-facing ADNI homepage which includes detailed instructions on accessing ADNI data and applying for access to biosample specimens collected in the study.

The ADNI website hosts other valuable resources, including answers to frequently asked questions and a database of “Ask the Experts” Q&A responses. The ADNI biostatistics core also maintains a google group for ADNI data users. Users of the R programming language can also take advantage of the ADNIMERGE R package.

This is currently a work in progress, and more information will be added over time.

The organization of this documentation

This documentation is organized into four primary sections:

  • About contains some essential background information about the ADNI study, and some basic information about the data set.

  • Getting Started contains some general guidance for working with the ADNI data set

  • Tables to know gives a high-level overview of some important tables in the data set that investigators may be particularly interested in.

  • Reference contains more detailed information about specific data types and tables.

Users who are already familiar with the ADNI study may wish to jump ahead to the ‘Getting Started’ section.