Evaluation of a Letter Intervention Promoting a Plant-based Diet

Evaluation of a Letter Intervention Among At-risk Adults Promoting a Plant-based Diet Using a Combination of Provider Testimonials, the Forks Over Knives Documentary, and Commitment- or Prevention-focused Behavioral Nudges

The researchers' mission is to promote healthier eating behavior and to reduce costs associated with healthcare. The purpose of this study is to evaluate the effects of mailing randomly selected participants a letter promoting a plant-based diet. Depending on the experimental condition, participants may additionally receive a free documentary, Forks Over Knives, and they may also get letters which use commitment- or prevention-focused messages to encourage watching the documentary and changing their eating behavior. The researchers hypothesize that receiving the documentary will be associated with lower insurance claims and improved health outcomes one and two years later. The researchers also hypothesize that using either commitment- or prevention-focused messages will also contribute to lower insurance claims and improved health outcomes compared to experimental conditions where materials did not include these messages. This study will help the researchers design evidence-supported programs that can improve people's health.

Study Overview

• Status: Completed
• Conditions: Cardiovascular Diseases; Obesity; Diabetes Mellitus
• Intervention / Treatment: Behavioral: Personal testimonial; Behavioral: Forks Over Knives Documentary; Behavioral: Commitment nudge; Behavioral: Prevention nudge

Detailed Description

Note that participant selection and assignment will be done at the level of the household, but analysis of outcomes will include individual-level analysis. This analytic decision was made because the researchers assume that the intervention may potentially affect other members of the household. While one person in a household will be selected for matching the eligibility criteria, the mailed materials will be addressed to all adult members of the household (defined as adults 18+ who are the spouse or child of the selected member) who are members of the Geisinger Health Plan. Outcome data will be pulled from all adult members of the household who have data through the Geisinger Health Plan.

The researchers will analyze the data using standard survey research analyses methods, including computing bivariate correlations, using general linear models, using non-parametric models for non-normally distributed insurance data, and entering variables as independent predictors in regression models to attempt to predict desired outcomes. The researchers will also use multilevel models to account for household- and individual-level data. The analysis of primary outcomes will focus on data one year after the intervention begins. Follow-up analysis on secondary outcomes will be conducted two years after the intervention begins. The researchers will conduct separate analyses of the selected participant (i.e., the individual who met the eligibility criteria) and other members of that participant's household. This will test whether there are any spillover effects of the intervention to other people in the household.

For clarity in this record, any discussion of sample size and participants refers to households, as this is the primary level for participant selection and assignment.

• Study Type: Interventional
• Enrollment (Actual): 11234
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Pennsylvania
    • Danville, Pennsylvania, United States, 17822
      • Geisinger Health System

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Has two out of the three following conditions:

  • Body mass index over 30
  • Diagnosis of type 2 diabetes (specifically with at least one medication)
  • Diagnosis of cardiovascular disease

• Has health insurance through Geisinger Health Plan (is an active member with a full 12-month enrollment in the previous year) under one of the following categories:

  • Medicare with required primary care provider
  • Medicaid
  • Individual policy under the Affordable Care Act
• Has visited their primary care provider in the past 12 months

Exclusion Criteria:

• Is institutionalized
• Has active cancer, cirrhosis, renal failure, dementia, or active psychosis
• Is in the same household as another selected participant

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Supportive Care
• Allocation: Randomized
• Interventional Model: Factorial Assignment
• Masking: Triple

Number of Arms

14

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
No Intervention: No contact control; Participants are not contacted.
Experimental: Letter; Participants are only contacted through a letter with a personal testimonial.	Behavioral: Personal testimonial; Participants will receive a letter promoting a plant-based diet. This letter will feature a personal testimonial about the benefits of a plant-based diet. Presenting this information to participants might encourage them to make behavioral changes to improve their health.
Experimental: Link and no nudge; Participants are sent the Forks Over Knives documentary online link and a letter with a personal testimonial and no nudges.	Behavioral: Personal testimonial; Participants will receive a letter promoting a plant-based diet. This letter will feature a personal testimonial about the benefits of a plant-based diet. Presenting this information to participants might encourage them to make behavioral changes to improve their health.; Behavioral: Forks Over Knives Documentary; Participants will be mailed the documentary Forks Over Knives, which provides scientific arguments promoting a plant-based and whole foods diet. The behavioral effect of this documentary comes from watching the documentary and potentially choosing to order a free cookbook (participants are given this opportunity in the letter accompanying the documentary). The effect of the diet itself is not a central part of the intervention, as people can choose to adopt or not adopt any part of the diet.
Experimental: Link and commitment nudge; Participants are sent the Forks Over Knives documentary online link and a letter with a personal testimonial and a commitment nudge.	Behavioral: Personal testimonial; Participants will receive a letter promoting a plant-based diet. This letter will feature a personal testimonial about the benefits of a plant-based diet. Presenting this information to participants might encourage them to make behavioral changes to improve their health.; Behavioral: Forks Over Knives Documentary; Participants will be mailed the documentary Forks Over Knives, which provides scientific arguments promoting a plant-based and whole foods diet. The behavioral effect of this documentary comes from watching the documentary and potentially choosing to order a free cookbook (participants are given this opportunity in the letter accompanying the documentary). The effect of the diet itself is not a central part of the intervention, as people can choose to adopt or not adopt any part of the diet.; Behavioral: Commitment nudge; At the end of the letter promoting a plant-based diet, participants will be asked to write dates and personal signatures committing to watching the documentary. They will be asked to mail back this written commitment. Stating one's intentions to implement certain behavior is meant to increase the likelihood of follow-up behavior. This request might nudge more people to watch the documentary and make some behavioral changes to prevent negative health outcomes.
Experimental: Link and prevention nudge; Participants are sent the Forks Over Knives documentary online link and a letter with a personal testimonial and a prevention nudge.	Behavioral: Personal testimonial; Participants will receive a letter promoting a plant-based diet. This letter will feature a personal testimonial about the benefits of a plant-based diet. Presenting this information to participants might encourage them to make behavioral changes to improve their health.; Behavioral: Forks Over Knives Documentary; Participants will be mailed the documentary Forks Over Knives, which provides scientific arguments promoting a plant-based and whole foods diet. The behavioral effect of this documentary comes from watching the documentary and potentially choosing to order a free cookbook (participants are given this opportunity in the letter accompanying the documentary). The effect of the diet itself is not a central part of the intervention, as people can choose to adopt or not adopt any part of the diet.; Behavioral: Prevention nudge; As part of the letter promoting a plant-based diet, one paragraph will describe the risks of not taking action. This phrasing reframes the status quo as contributing to future loss (e.g., costs of medication and operations). In effect, the letter encourages participants to focus on preventing this loss by taking action. This additional text might nudge more people to watch the documentary and make some behavioral changes to prevent negative health outcomes.
Experimental: Link and both nudges; Participants are sent the Forks Over Knives documentary online link and a letter with a personal testimonial and both commitment and prevention nudges.	Behavioral: Personal testimonial; Participants will receive a letter promoting a plant-based diet. This letter will feature a personal testimonial about the benefits of a plant-based diet. Presenting this information to participants might encourage them to make behavioral changes to improve their health.; Behavioral: Forks Over Knives Documentary; Participants will be mailed the documentary Forks Over Knives, which provides scientific arguments promoting a plant-based and whole foods diet. The behavioral effect of this documentary comes from watching the documentary and potentially choosing to order a free cookbook (participants are given this opportunity in the letter accompanying the documentary). The effect of the diet itself is not a central part of the intervention, as people can choose to adopt or not adopt any part of the diet.; Behavioral: Commitment nudge; At the end of the letter promoting a plant-based diet, participants will be asked to write dates and personal signatures committing to watching the documentary. They will be asked to mail back this written commitment. Stating one's intentions to implement certain behavior is meant to increase the likelihood of follow-up behavior. This request might nudge more people to watch the documentary and make some behavioral changes to prevent negative health outcomes.; Behavioral: Prevention nudge; As part of the letter promoting a plant-based diet, one paragraph will describe the risks of not taking action. This phrasing reframes the status quo as contributing to future loss (e.g., costs of medication and operations). In effect, the letter encourages participants to focus on preventing this loss by taking action. This additional text might nudge more people to watch the documentary and make some behavioral changes to prevent negative health outcomes.
Experimental: DVD and no nudge; Participants are sent the Forks Over Knives documentary DVD and a letter with a personal testimonial and no behavioral nudges.	Behavioral: Personal testimonial; Participants will receive a letter promoting a plant-based diet. This letter will feature a personal testimonial about the benefits of a plant-based diet. Presenting this information to participants might encourage them to make behavioral changes to improve their health.; Behavioral: Forks Over Knives Documentary; Participants will be mailed the documentary Forks Over Knives, which provides scientific arguments promoting a plant-based and whole foods diet. The behavioral effect of this documentary comes from watching the documentary and potentially choosing to order a free cookbook (participants are given this opportunity in the letter accompanying the documentary). The effect of the diet itself is not a central part of the intervention, as people can choose to adopt or not adopt any part of the diet.
Experimental: DVD and commitment nudge; Participants are sent the Forks Over Knives documentary DVD and a letter with a personal testimonial and a commitment nudge.	Behavioral: Personal testimonial; Participants will receive a letter promoting a plant-based diet. This letter will feature a personal testimonial about the benefits of a plant-based diet. Presenting this information to participants might encourage them to make behavioral changes to improve their health.; Behavioral: Forks Over Knives Documentary; Participants will be mailed the documentary Forks Over Knives, which provides scientific arguments promoting a plant-based and whole foods diet. The behavioral effect of this documentary comes from watching the documentary and potentially choosing to order a free cookbook (participants are given this opportunity in the letter accompanying the documentary). The effect of the diet itself is not a central part of the intervention, as people can choose to adopt or not adopt any part of the diet.; Behavioral: Commitment nudge; At the end of the letter promoting a plant-based diet, participants will be asked to write dates and personal signatures committing to watching the documentary. They will be asked to mail back this written commitment. Stating one's intentions to implement certain behavior is meant to increase the likelihood of follow-up behavior. This request might nudge more people to watch the documentary and make some behavioral changes to prevent negative health outcomes.
Experimental: DVD and prevention nudge; Participants are sent the Forks Over Knives documentary DVD and a letter with a personal testimonial and a prevention nudge.	Behavioral: Personal testimonial; Participants will receive a letter promoting a plant-based diet. This letter will feature a personal testimonial about the benefits of a plant-based diet. Presenting this information to participants might encourage them to make behavioral changes to improve their health.; Behavioral: Forks Over Knives Documentary; Participants will be mailed the documentary Forks Over Knives, which provides scientific arguments promoting a plant-based and whole foods diet. The behavioral effect of this documentary comes from watching the documentary and potentially choosing to order a free cookbook (participants are given this opportunity in the letter accompanying the documentary). The effect of the diet itself is not a central part of the intervention, as people can choose to adopt or not adopt any part of the diet.; Behavioral: Prevention nudge; As part of the letter promoting a plant-based diet, one paragraph will describe the risks of not taking action. This phrasing reframes the status quo as contributing to future loss (e.g., costs of medication and operations). In effect, the letter encourages participants to focus on preventing this loss by taking action. This additional text might nudge more people to watch the documentary and make some behavioral changes to prevent negative health outcomes.
Experimental: DVD and both nudges; Participants are sent the Forks Over Knives documentary DVD and a letter with a personal testimonial and both commitment and prevention nudges.	Behavioral: Personal testimonial; Participants will receive a letter promoting a plant-based diet. This letter will feature a personal testimonial about the benefits of a plant-based diet. Presenting this information to participants might encourage them to make behavioral changes to improve their health.; Behavioral: Forks Over Knives Documentary; Participants will be mailed the documentary Forks Over Knives, which provides scientific arguments promoting a plant-based and whole foods diet. The behavioral effect of this documentary comes from watching the documentary and potentially choosing to order a free cookbook (participants are given this opportunity in the letter accompanying the documentary). The effect of the diet itself is not a central part of the intervention, as people can choose to adopt or not adopt any part of the diet.; Behavioral: Commitment nudge; At the end of the letter promoting a plant-based diet, participants will be asked to write dates and personal signatures committing to watching the documentary. They will be asked to mail back this written commitment. Stating one's intentions to implement certain behavior is meant to increase the likelihood of follow-up behavior. This request might nudge more people to watch the documentary and make some behavioral changes to prevent negative health outcomes.; Behavioral: Prevention nudge; As part of the letter promoting a plant-based diet, one paragraph will describe the risks of not taking action. This phrasing reframes the status quo as contributing to future loss (e.g., costs of medication and operations). In effect, the letter encourages participants to focus on preventing this loss by taking action. This additional text might nudge more people to watch the documentary and make some behavioral changes to prevent negative health outcomes.
Experimental: Link and DVD and no nudge; Participants are sent the Forks Over Knives documentary online link and DVD and a letter with a personal testimonial and no behavioral nudges.	Behavioral: Personal testimonial; Participants will receive a letter promoting a plant-based diet. This letter will feature a personal testimonial about the benefits of a plant-based diet. Presenting this information to participants might encourage them to make behavioral changes to improve their health.; Behavioral: Forks Over Knives Documentary; Participants will be mailed the documentary Forks Over Knives, which provides scientific arguments promoting a plant-based and whole foods diet. The behavioral effect of this documentary comes from watching the documentary and potentially choosing to order a free cookbook (participants are given this opportunity in the letter accompanying the documentary). The effect of the diet itself is not a central part of the intervention, as people can choose to adopt or not adopt any part of the diet.
Experimental: Link and DVD and commitment nudge; Participants are sent the Forks Over Knives documentary online link and DVD and a letter with a personal testimonial and a commitment nudge.	Behavioral: Personal testimonial; Participants will receive a letter promoting a plant-based diet. This letter will feature a personal testimonial about the benefits of a plant-based diet. Presenting this information to participants might encourage them to make behavioral changes to improve their health.; Behavioral: Forks Over Knives Documentary; Participants will be mailed the documentary Forks Over Knives, which provides scientific arguments promoting a plant-based and whole foods diet. The behavioral effect of this documentary comes from watching the documentary and potentially choosing to order a free cookbook (participants are given this opportunity in the letter accompanying the documentary). The effect of the diet itself is not a central part of the intervention, as people can choose to adopt or not adopt any part of the diet.; Behavioral: Commitment nudge; At the end of the letter promoting a plant-based diet, participants will be asked to write dates and personal signatures committing to watching the documentary. They will be asked to mail back this written commitment. Stating one's intentions to implement certain behavior is meant to increase the likelihood of follow-up behavior. This request might nudge more people to watch the documentary and make some behavioral changes to prevent negative health outcomes.
Experimental: Link and DVD and prevention nudge; Participants are sent the Forks Over Knives documentary online link and DVD and a letter with a personal testimonial and a prevention nudge.	Behavioral: Personal testimonial; Participants will receive a letter promoting a plant-based diet. This letter will feature a personal testimonial about the benefits of a plant-based diet. Presenting this information to participants might encourage them to make behavioral changes to improve their health.; Behavioral: Forks Over Knives Documentary; Participants will be mailed the documentary Forks Over Knives, which provides scientific arguments promoting a plant-based and whole foods diet. The behavioral effect of this documentary comes from watching the documentary and potentially choosing to order a free cookbook (participants are given this opportunity in the letter accompanying the documentary). The effect of the diet itself is not a central part of the intervention, as people can choose to adopt or not adopt any part of the diet.; Behavioral: Prevention nudge; As part of the letter promoting a plant-based diet, one paragraph will describe the risks of not taking action. This phrasing reframes the status quo as contributing to future loss (e.g., costs of medication and operations). In effect, the letter encourages participants to focus on preventing this loss by taking action. This additional text might nudge more people to watch the documentary and make some behavioral changes to prevent negative health outcomes.
Experimental: Link and DVD and both nudges; Participants are sent the Forks Over Knives documentary online link and DVD and a letter with a personal testimonial and both commitment and prevention nudges.	Behavioral: Personal testimonial; Participants will receive a letter promoting a plant-based diet. This letter will feature a personal testimonial about the benefits of a plant-based diet. Presenting this information to participants might encourage them to make behavioral changes to improve their health.; Behavioral: Forks Over Knives Documentary; Participants will be mailed the documentary Forks Over Knives, which provides scientific arguments promoting a plant-based and whole foods diet. The behavioral effect of this documentary comes from watching the documentary and potentially choosing to order a free cookbook (participants are given this opportunity in the letter accompanying the documentary). The effect of the diet itself is not a central part of the intervention, as people can choose to adopt or not adopt any part of the diet.; Behavioral: Commitment nudge; At the end of the letter promoting a plant-based diet, participants will be asked to write dates and personal signatures committing to watching the documentary. They will be asked to mail back this written commitment. Stating one's intentions to implement certain behavior is meant to increase the likelihood of follow-up behavior. This request might nudge more people to watch the documentary and make some behavioral changes to prevent negative health outcomes.; Behavioral: Prevention nudge; As part of the letter promoting a plant-based diet, one paragraph will describe the risks of not taking action. This phrasing reframes the status quo as contributing to future loss (e.g., costs of medication and operations). In effect, the letter encourages participants to focus on preventing this loss by taking action. This additional text might nudge more people to watch the documentary and make some behavioral changes to prevent negative health outcomes.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Medical Cost in US Dollars From One Year Before to One Year After Intervention	Total annual amount of medical and pharmacy costs (sum) as reported by Geisinger Health Plan. General linear models are used to model change between the data from the year before the intervention and the data from one year after intervention. Lower costs is the desirable outcome.	2 years
Number of Visits From One Year Before to One Year After Intervention	Total number of primary care physician and specialist visits (sum) as reported by Geisinger Health Plan. General linear models are used to model change between the data from the year before the intervention and the data from one year after intervention. Fewer visits is the desirable outcome.	2 years
Number of Prescriptions From One Year Before to One Year After Intervention	Total number of prescriptions (fills) as reported by Geisinger Health Plan. General linear models are used to model change between the data from the year before the intervention and the data from one year after intervention. Fewer prescriptions is the desirable outcome.	2 years
Number of Unique Prescribed Medication From One Year Before to One Year After Intervention	Total number of unique prescribed medication in the past year as reported by Geisinger Health Plan. General linear models are used to model change between the data from the year before the intervention and the data from one year after intervention. Less unique prescribed medication is the desirable outcome.	2 years
Body Mass Index From One Year Before to One Year After Intervention	Taken from annual checkup with primary care provider. Computed from height (in meters) and weight (in kilograms) data with the formula kilograms/meters^2. General linear models are used to model change between the data from the year before the intervention and the data from one year after intervention. A body mass index between the range of 18.5 to 25 is the desirable outcome.	2 years
Systolic Blood Pressure From One Year Before to One Year After Intervention	Taken from annual checkup with primary care provider. General linear models are used to model change between the data from the year before the intervention and the data from one year after intervention. Systolic blood pressure that is 120 millimeters of mercury (mmHg) or less is the desirable outcome.	2 years
Diastolic Blood Pressure From One Year Before to One Year After Intervention	Taken from annual checkup with primary care provider. General linear models are used to model change between the data from the year before the intervention and the data from one year after intervention. Systolic blood pressure that is 80 millimeters of mercury (mmHg) or less is the desirable outcome.	2 years

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Triglyceride Levels From One Year Before to One Year After Intervention	One component of cholesterol, used if data is on health record. A triglyceride level of 150 milligrams per deciliter (mg/dl) or lower is the desirable outcome.	2 years
Low-density Lipoprotein (LDL) Levels From One Year Before to One Year After Intervention	One component of cholesterol, used if data is on health record. An LDL level of 100 milligrams per deciliter (mg/dl) or lower is the desirable outcome.	2 years
High-density Lipoprotein (HDL) Levels From One Year Before to One Year After Intervention	One component of cholesterol, used if data is on health record. An HDL level of 60 milligrams per deciliter (mg/dl) or higher is the desirable outcome.	2 years
Low-density Lipoprotein/High-density Lipoprotein (LDL/HDL) Ratios From One Year Before to One Year After Intervention	Computed as the ratio of LDL/HDL. An LDL/HDL ratio of 3 or less for men and 2.5 or less for women is the desirable outcome.	2 years
Hemoglobin A1c (hbA1c) From One Year Before to One Year After Intervention	Test for diabetes, used if data is on health record. Percentage score reflects blood-glucose levels. An hbA1c level of 5.7% or lower is the desirable outcome.	2 years
Medical Cost in US Dollars From Five Years Before to Two Years After Intervention (Extended Time Frame)	Total annual amount of medical and pharmacy costs (sum) as reported by Geisinger Health Plan. Lower costs is the desirable outcome.	7 years
Number of Visits From Five Years Before to Two Years After Intervention (Extended Time Frame)	Total number of primary care physician and specialist visits (sum) as reported by Geisinger Health Plan. Fewer visits is the desirable outcome.	7 years
Number of Prescriptions From Five Years Before to Two Years After Intervention (Extended Time Frame)	Total number of prescriptions (standard unit is prescription per number of days supplied) as reported by Geisinger Health Plan. Fewer prescriptions is the desirable outcome.	7 years
Number of Unique Prescribed Medication From Five Years Before to Two Years After Intervention (Extended Time Frame)	Total number of unique prescribed medication in the past year as reported by Geisinger Health Plan. Less unique prescribed medication is the desirable outcome.	7 years
Body Mass Index From Five Years Before to Two Years After Intervention (Extended Time Frame)	Taken from annual checkup with primary care provider. Computed from height (in meters) and weight (in kilograms) data with the formula kilograms/meters^2. A body mass index between the range of 18.5 to 25 is the desirable outcome.	7 years
Systolic Blood Pressure From Five Years Before to Two Years After Intervention (Extended Time Frame)	Taken from annual checkup with primary care provider. Systolic blood pressure that is 120 millimeters of mercury (mmHg) or less is the desirable outcome.	7 years
Diastolic Blood Pressure From Five Years Before to Two Years After Intervention (Extended Time Frame)	Taken from annual checkup with primary care provider. Systolic blood pressure that is 80 millimeters of mercury (mmHg) or less is the desirable outcome.	7 years
Triglyceride Levels From Five Years Before to Two Years After Intervention (Extended Time Frame)	One component of cholesterol, used if data is on health record. A triglyceride level of 150 milligrams per deciliter (mg/dl) or lower is the desirable outcome.	7 years
Low-density Lipoprotein (LDL) Levels From Five Years Before to Two Years After Intervention (Extended Time Frame)	One component of cholesterol, used if data is on health record. An LDL level of 100 milligrams per deciliter (mg/dl) or lower is the desirable outcome.	7 years
High-density Lipoprotein (HDL) Levels From Five Years Before to Two Years After Intervention (Extended Time Frame)	One component of cholesterol, used if data is on health record. An HDL level of 60 milligrams per deciliter (mg/dl) or higher is the desirable outcome.	7 years
Low-density Lipoprotein/High-density Lipoprotein (LDL/HDL) Ratios From Five Years Before to Two Years After Intervention (Extended Time Frame)	Computed as the ratio of LDL/HDL. An LDL/HDL ratio of 3 or less for men and 2.5 or less for women is the desirable outcome.	7 years
Hemoglobin A1c (hbA1c) From Five Years Before to Two Years After Intervention (Extended Time Frame)	Test for diabetes, used if data is on health record. Percentage score reflects blood-glucose levels. An hbA1c level of 5.7% and below is the desirable outcome.	7 years
Five Years Before to Two Years After Intervention in Depressed Mood and Anhedonia as Assessed by the Patient Health Questionnaire-2 (PHQ-2) (Extended Time Frame)	Assesses depressed mood and anhedonia in the past two weeks; used if data is on health record. The sum of two items (each scored 0-3) is computed with a total score range of 0-6. A lower score is the desired outcome.	7 years
Values From One Year Before to One Year After Intervention of Depressed Mood and Anhedonia as Assessed by the Patient Health Questionnaire-2 (PHQ-2)	Although originally listed as secondary, this outcome measure was intended to be exploratory. Due to the largely null pattern of results on the primary outcomes, it was decided to forgo additional analysis at this time.	2 years

Collaborators and Investigators

• Sponsor: Geisinger Clinic
• Investigators: Principal Investigator: Amir Goren, PhD, Program Director; Study Director: Henri Carlo Y Santos, PhD, Post-doctoral Fellow; Study Director: Christopher Chabris, PhD, Professor; Study Director: Michelle N Meyer, PhD, JD, Assistant Professor; Study Director: Allison Hess, BS, Vice President

Publications and helpful links

General Publications

• Milkman KL, Beshears J, Choi JJ, Laibson D, Madrian BC. Using implementation intentions prompts to enhance influenza vaccination rates. Proc Natl Acad Sci U S A. 2011 Jun 28;108(26):10415-20. doi: 10.1073/pnas.1103170108. Epub 2011 Jun 13.
• Tversky A, Kahneman D. The framing of decisions and the psychology of choice. Science. 1981 Jan 30;211(4481):453-8. doi: 10.1126/science.7455683.

Helpful Links

• The trailer for the Forks Over Knives Documentary that will be sent for free to participants in the relevant arms

Study record dates

Study Major Dates

• Study Start (Actual): June 20, 2019
• Primary Completion (Actual): June 30, 2020
• Study Completion (Actual): June 30, 2022

Study Registration Dates

• First Submitted: March 14, 2019
• First Submitted That Met QC Criteria: March 15, 2019
• First Posted (Actual): March 19, 2019

Study Record Updates

• Last Update Posted (Estimated): May 20, 2025
• Last Update Submitted That Met QC Criteria: May 1, 2025
• Last Verified: May 1, 2025

More Information

Terms related to this study

• Keywords: Randomized controlled trial; Chronic disease; Plant-based diet; Commitment; Behavioral nudge; Health behaviors; Mail distribution; Insurance claims; Letter-based intervention; Prevention focus; Loss framing; Provider testimonial
• Additional Relevant MeSH Terms: Cardiovascular Diseases
• Other Study ID Numbers: 2019-0179

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Data with no personally identifiable information will be made available to other researchers on the Open Science Framework for transparency. This will include preregistered hypotheses, analysis plan and code, and the essential data needed to replicate the analysis that yielded reported findings.
• IPD Sharing Time Frame: The data will become available upon publication and will be available as long as the Open Science Framework hosts the data.
• IPD Sharing Access Criteria: The data on the Open Science Framework will be open to anyone requesting that information.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ANALYTIC_CODE

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No