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Participants Years enrollment close-out today
Baseline Questionnaire (BQ) ~154,000 1993-2001
Dietary Questionnaire I-only (DQX) ~63,000 1993-2001
Diet History Questionnaire (DHQ) ~119,000 1998-2004
Supplemental Questionnaire (SQX) ~104,000 2006-2007
Medical Use Questionnaire (MUQ) ~60,000 2013
Brief Survey (BCQ) ~47,000 2017-2018
Collection of Cancers
Collection of Mortality

Diet History (DHQ)


Timeline from T0 to T13 showing the collection of diet history questionnaires (DHQ) in the trial. Median completion of the DHQ was T3 for both arms of the trial, but ranges were different. Collection of DHQ from the intervention arm occurred mostly between T3 and T5, while the control arm spanned from T0 to T5.

The Diet History Questionnaire (DHQ) contains dietary information similar to that found in the DQX. 77% of all participants in both arms of the trial completed the DHQ. The form was introduced 5 years into the trial (December 1998). Raw questionnaire responses were processed into analysis-ready variables in terms of gram intake, pyramid servings, food frequencies per day, etc.

Participants in the control arm randomized prior to December 1998 were offered the DHQ in 1999 or 2000, generally around the anniversary of randomization in either year. Control arm participants randomized in/after December 1998 were offered the DHQ at baseline.

Participants in the intervention arm who were randomized prior to December 1995 were offered the DHQ in 1999, generally around the anniversary of randomization. Intervention arm participants randomized in/after December 1995 (third anniversary in/after December 1998) were offered the DHQ generally around their third anniversary of randomization (T3).

DHQ data can be obtained in the DHQ dataset.

Summary Available Data
  • Participant-reported data
  • Covers 113,000 participants
  • Introduced in 1998
  • Median time into study collected: 3 years
  • Median time post-collection: 9 years
  • Forms used:
  • Form completion details
  • Alcohol use
  • Nutrient intake
  • Supplement intake
  • Glycemic index/load
  • Meat-specific variables
  • Pyramid servings
  • Daily grams of various foods and beverages
  • Daily frequencies of various foods and beverages
  • Raw questionnaire responses
Time of Data Acquisition

Three timelines from T0 to T13 showing the collection of diet history questionnaires (DHQ) from both arms in the trial. The first timeline is for 27,000 participants randomized before December 1995. The DHQ was completed between T4 and T6. The second timeline is for 56,000 participants randomized between December 1995 and December 1998. The DHQ was completed around T3 for both arms, but the collection from the control arm is over a slightly wider range than the intervention arm. The third timeline is for 31,000 participants randomized after December 1998. Again, most of the intervention arm completed the DHQ around T3, but the DHQ was completed by the control arm much earlier, around T0.