Overview of Public Access Data Sets - Intervention and Post-Intervention Phases

Data from the Look AHEAD trial, Action for Health in Diabetes, include Intervention Phase results with new data from Ancillary Study and Post-Intervention Phase results. These can be accessed through application to the National Institute of Diabetes and Digestive and Kidney Diseases; NIDDK Central Repository: https://repository.niddk.nih.gov/studies/look-ahead/. . Look AHEAD Principal Investigators may access the full data archive directly from the Look AHEAD site after login.

The Intervention Phase involves baseline and follow-up data from two randomized groups: Diabetes Support and Education, or Intensive Lifestyle Intervention. The trial enrollment began in 2001 with follow-up continuing through September 14, 2012, when the intensive intervention was stopped. The recommendation from the National Institutes of Health (NIH) directed that the Intensive Lifestyle Intervention be concluded, with an intent to continue studying the benefits and risks of the intervention. Data collection continued in 2012 and 2013, with a protocol directed Continuation Study starting in 2013. In this archive, Post-intervention Phase data are included through 2015. Data collection on the cohort continues through 2020 on post-intervention participants. Additional updates are planned as data become available.

The trial cohort began with 5145 participants. Consented and randomized participants, only, are included in this archive; those participants participating from Native American sites are excluded, per consent limitations, resulting in a cohort of 4901. Data collected during the Intervention Phase covers an approximately 10-year period. Study outcome data are included, describing time to first event within the Intervention Phase: primary, secondary, and other cardiovascular events. The adjudication process for determining all study outcomes (Mortality, Cardiovascular Events, Cancer, and Fractures) is in process; these data are also planned for future updates.

An Ancillary study: Cognitive and Physical Functioning, involving new data collection, was initiated during Year 8 of the Intervention Phase on a subset of participants. Follow-up or initial assessments in a second ancillary study, also on a subset of participants, was completed in approximately Year 10. Specific aims for the Continuation Study in the Post-Intervention Phase focused on cognitive and physical functioning, resulting in a third round of follow-up or initial assessments on participants. As such, one to three sets of battery assessments have been administered to participants. Approximately 20% of the data were collected during the Intervention Phase. NIH Toolbox Cognition Domain measurements were collected once on a subset of participants, all during Post-Intervention. Cognitive battery assessments are available on 3717 participants (5123 assessments) and NIH Toolbox data on 1004 participants. Mobility disability, measured and adjudicated from initial physical function assessments, are available for 3620 participants.

The Post-Intervention Phase covers a three-year period of data collection after the intervention was stopped, including many of the same measurements and questionnaires collected during intervention. There was a one-year period of data collection that continued following the Intervention Phase, prior to the initiation of the Continuation Study. 4365 participants participated in the Post-Intervention Phase; 4201 consented to the Continuation Study for either phone contact or clinic visits with 3659 making a clinic visit.

Descriptions of available data are provided in pdf files and organized as follows:

1. Overview
2. Available Data
   1. Key Data
   2. Intervention Phase Results
   3. Cognitive Function Results
   4. Physical Function Results
   5. Post-Intervention Results

The Overview offers a brief orientation to the Look AHEAD study and outlines data available in the archive. Available Data provides Contents Listings of Variables, Summary Statistics, and Data Collection Forms. Illustrations of forms include the data entry screen shot which displays variable names in context with value definitions; these are concatenated with the data collection form used at the clinical centers.

Under “Key Data” are descriptions of essential variables that can be mapped to all data sets and primary outcome data. Intervention and Post-Intervention Results include: “Measures”, descriptions of data relating to physical measurements, study assessments, or electronically captured data; and, “Questionnaires”, descriptions of data relating to most data collections forms. Cognitive and Physical Function Results combine Ancillary Study and Post-Intervention Results.

Data sets largely provide recurring data for each participant starting with screening, covering randomization, and biannual visits during Intervention or yearly visits during Post-Intervention; see data availability for scheduled follow-up, as each measurement or questionnaire differs in follow-up pattern. Data collection forms were modified as needed during the operation of the trial. The final versions of forms are presented in this archive.

Guidelines followed for data preparation in this release comply with the regulations of the Health Insurance Portability and Accountability Act (HIPAA), eliminating all variables including personal identifying information. Further de-identification of participants is obtained by exchanging original study identifiers with randomly assigned identifiers. All dates have been exchanged with variables expressed in relation to days according to randomization.