Evaluation of Reminder Strategies (Emails and Text Messages) to Increase Participation in the Le French Gut E-cohort

Le French Gut: Randomized-Controlled Trial to Evaluate Reminder Strategies (Emails and Text Messages) to Increase Participation in the Le French Gut E-cohort

This study is a randomized controlled trial nested in the "Le French Gut" e-cohort aiming to test the efficacy of 4 reminder strategies (emails and/or SMS with standard and/or institutional wording) in increasing participation of inactive volunteers.

This trial is led in collaboration between the "Le French Gut" project and SKEZI, a DeepTech start-up which markets the data collection solution (SKEZIA online platform) for the "Le French Gut" project and carries out the InnoPRO program, aimed at generating new knowledge in the field of e-cohorts.

Study Overview

• Status: Completed
• Conditions: General Population (no Specific Condition or Disease)
• Intervention / Treatment: Other: 3 standard email reminders; Other: 3 institutional email reminders; Other: 3 SMS reminders; Other: Combined reminders

Detailed Description

The "Le French Gut" project (NCT05758961) is an ongoing online research cohort aiming to collect faecal samples and associated nutritional and clinical data to better understand the observed heterogeneity between gut microbiome of healthy subjects, its connections with the diet and lifestyle, but also changes in gut microbiota associated with diseases (diabetes, obesity, allergies, cancer, Parkinson, Alzheimer…). Le French Gut is initiated by MetaGenoPolis-INRAE, supported by INRAE with Prof. R. Benamouzig, (AP-HP) as principal investigator of the project.

When participants first register to participate in the cohort, they must complete a short "About You" ("A propos de vous") questionnaire before they can receive any study kits and be considered as active participants in the research. In October 2024, almost half of the ~43,000 individuals who have created an account never finish this first questionnaire needed to validate their participation in the cohort.

Purpose of the study This study will test which type of reminder works best for encouraging those inactive volunteers to return to the platform and complete the missing questionnaire.

How the study will be done

All eligible volunteers (i.e. people who registered on the online platform and provided a valid e mail address or mobile number but have not yet finished completing the "A propos de vous" questionnaire) will be randomly assigned to one of four groups:

1. Standard e mail - a regular, semi-formal email. Same email sent three times, 72h apart.
2. SMS - a short text message sent to the participant's phone. Same SMS sent three times, 72h apart.
3. Institutional e mail - a plain, formal email signed by the "Le French Gut" study coordinator. Same email sent three times, 72h apart.
4. Combined sequence - a standard e mail, followed 72 hours later by the SMS, and 72 hours after that by the institutional e mail.

All messages contain the same content (a link that takes the participant directly to the questionnaire). The study will last about one month after the last reminder is sent.

Questions the study will answer

• Which reminder method results in the highest completion rate of the "A propos de vous" questionnaire (i.e. proportion of people completing the questionnaire) within 30 days?
• How quickly do participants respond after each type of reminder?
• Does the time since a person first registered (recent vs. long time registrant) influence which reminder works best?

Hypothesis Investigators hypothesized that the combined sequence (standard e mail → SMS → institutional e mail) will lead to a higher proportion of participants completing the questionnaire than any single channel reminder alone.

Why this matters Finding the most effective, low cost reminder strategy will help the French Gut team-and other online cohorts-keep more participants engaged, thereby improving the quantity and quality of the data that can be used for future health research. The results will be shared in a peer reviewed scientific article and could guide the design of future e cohort studies worldwide.

• Study Type: Interventional
• Enrollment (Actual): 20487
• Phase: Not Applicable

Contacts and Locations

Study Locations

• France
  • Paris, France
    • SKEZI

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Being registered on the "Le French Gut" platform but not active participant (e.i. eligibility questionnaire not completed, "Le French Gut" consent not validated, "A propos de vous" questionnaire not completed)
• Having provided a valid email address and/or mobile-phone number

Exclusion Criteria:

• Completed "A propos de vous" questionnaire before the first reminder
• Being non eligible to the "Le French Gut" cohort (eligibility to "Le Fench Gut" cohort: being over 18 years-old and living in France)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: standard emails only; Standard, semi-formal worded email inviting participants to complete the online "A propos de vous" (personal information) questionnaire in order to validate their participation in the "Le French Gut" cohort.	Other: 3 standard email reminders; The same standard email is sent three times to participants, each email spaced 72 hours apart.
Experimental: institutional emails only; Institutional, formal-worded email, signed by the study coordinator, inviting participants to complete the online "A propos de vous" (personal information) questionnaire in order to validate their participation in the "Le French Gut" cohort.	Other: 3 institutional email reminders; The same institutional email is sent three times to participants, each email spaced 72 hours apart.
Experimental: SMS only; Short text message inviting participants to complete the online "A propos de vous" (personal information) questionnaire in order to validate their participation in the "Le French Gut" cohort.	Other: 3 SMS reminders; The same SMS (brief text message) is sent three times to participants, each SMS spaced 72 hours apart.
Experimental: Combined reminders; Combined sequence of reminders: first, the standard email; second, the SMS; third, the institutional email. The contents of the reminders are similar to those of the three other parallel groups inviting participants to complete the online "A propos de vous" (personal information) questionnaire in order to validate their participation in the "Le French Gut" cohort.	Other: Combined reminders; Three reminders are sent to participants, each reminder spaced 72 hours apart: the first reminder is a standard email, the second reminder is a SMS, the third reminder is a institutional email.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Completion rate	Proportion of participants who complete the "A propos de vous" questionnaire within 30 days after the last reminder, calculated as number of participants who fully completed the questionnaire divided by total number of participants included in the study (or arm)	30 days post-reminder

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Completion time	Time (in hours) between the date the last reminder was sent to a participant and the date of questionnaire completion	30 days post-reminder
Login rate	Number of participants who logged into their account divided by total number of participants included in the study (or arm)	30 days post-reminder
Login time	Time (in hours) between the date the final reminder was sent to a participant and the date of their next login to the platform	30 days post-reminder

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Email opening rate	Number of opened emails divided by number of delivered emails	30 days post-reminder
Email click-through rate	Number of participants who clicked on the link in the email divided by number of opened emails	30 days post-reminder

Collaborators and Investigators

• Sponsor: SKEZI
• Collaborators: Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement
• Investigators: Principal Investigator: Jean-Philippe Bertocchio, MD, PhD, SKEZI

Study record dates

Study Major Dates

• Study Start (Actual): November 7, 2024
• Primary Completion (Actual): November 25, 2024
• Study Completion (Actual): November 25, 2024

Study Registration Dates

• First Submitted: March 11, 2026
• First Submitted That Met QC Criteria: March 11, 2026
• First Posted (Actual): March 16, 2026

Study Record Updates

• Last Update Posted (Actual): March 17, 2026
• Last Update Submitted That Met QC Criteria: March 14, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: response rate; completion; inclusion; e-cohort; reminder strategy; email reminder; text message reminder
• Additional Relevant MeSH Terms: Pathologic Processes; Pathological Conditions, Signs and Symptoms; Disease
• Other Study ID Numbers: LFGxSKEZI-2024-001

Drug and device information, study documents

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