UMIN-ICDS Clinical Trial

Public title

Effects of Nudge-Based Messages on Participation in Community Gathering Places ("Kayoi-no-ba") Among Older Adults

Acronym

Nudges to Promote Participation in Community Gathering Places ("Kayoi-no-ba")

Scientific Title

Effects of Nudge-Based Messages on Participation in Community Gathering Places ("Kayoi-no-ba") Among Older Adults

Scientific Title:Acronym

Nudges to Promote Participation in Community Gathering Places ("Kayoi-no-ba")

Region

Japan

Condition

No specific condition

Classification by specialty

Not applicable

Classification by malignancy

Others

Genomic information

NO

Narrative objectives1

This study aimed to evaluate, through a randomized controlled trial, the effects of three nudge-based interventions-loss framing, social norms, and precommitment-on immediate intention to participate and self-reported participation two months later in community gathering places ("Kayoi-no-ba") among adults aged 60 years or older in Japan who were not currently participating, and to examine whether these effects differed by sex.

Basic objectives2

Efficacy

Basic objectives -Others

Trial characteristics_1

Confirmatory

Trial characteristics_2

Explanatory

Developmental phase

Not applicable

Primary outcomes

Proportion of participants reporting participation in community gathering places ("Kayoi-no-ba") approximately two months after the intervention. Participation frequency is assessed using six response options and dichotomised as no participation ("no participation") or participation (any of the other five response options).

Key secondary outcomes

Proportion of participants expressing an intention to participate in community gathering places ("Kayoi-no-ba") immediately after the intervention. Desired participation frequency is assessed using six response options and dichotomised as no intention to participate ("I do not want to participate") or intention to participate (any of the other five response options).

Study type

Interventional

Basic design

Parallel

Randomization

Randomized

Randomization unit

Individual

Blinding

Single blind -participants are blinded

Control

Active

Stratification

NO

Dynamic allocation

NO

Institution consideration

Institution is not considered as adjustment factor.

Blocking

NO

Concealment

Central registration

No. of arms

4

Purpose of intervention

Prevention

Type of intervention

Behavior,custom

Interventions/Control_1

A loss-framed message is presented once in Japanese. The message emphasises the potential disadvantages of not participating in community gathering places ("Kayoi-no-ba"), including age-related declines in physical and mental functioning, reductions in activities that can be performed independently and in social interaction, and the financial burden of care costs if long-term care becomes necessary.

Interventions/Control_2

A social-norm message is presented once in Japanese. The message states that many participants in community gathering places ("Kayoi-no-ba") decided to join because people around them were participating and that resident-led opportunities for building social connections are expanding, thereby highlighting others' participation.

Interventions/Control_3

A precommitment prompt is presented once in Japanese, asking participants to specify when and in which types of activities they would participate if they chose to join community gathering places ("Kayoi-no-ba"). Timing options are "this week", "this month", "next month", "this year", "next year or later" and "no participation".

Interventions/Control_4

Only an explanation of community gathering places ("Kayoi-no-ba") and a general invitation to participate are presented once in Japanese. The explanation describes "Kayoi-no-ba" as locally accessible gatherings held at least once per month for activities intended to prevent frailty and functional decline.

Interventions/Control_5

Interventions/Control_6

Interventions/Control_7

Interventions/Control_8

Interventions/Control_9

Interventions/Control_10

Age-lower limit

60

years-old

<=

Age-upper limit

Not applicable

Gender

Male and Female

Key inclusion criteria

1. Aged 60 years or older.
2. Residing in Japan.
3. Not certified as requiring support or long-term care under Japan's long-term care insurance system.
4. Not currently participating in community gathering places ("Kayoi-no-ba") at the time of screening.

Key exclusion criteria

1. Aged younger than 60 years.
2. Not residing in Japan.
3. Certified as requiring support or long-term care under Japan's long-term care insurance system.
4. Currently participating in community gathering places ("Kayoi-no-ba") at the time of screening.

Target sample size

2000

Name of lead principal investigator

1st name	Chenyue
Middle name
Last name	Huang

Organization

Institute for Health Economics and Policy

Division name

Research Department

Zip code

1050001

Address

3F, Tokyu Toranomon Building, 1-21-19 Toranomon, Minato-ku, Tokyo, Japan

TEL

0335068529

Email

shinetsu.ko@ihep.jp

Name of contact person

1st name	Chenyue
Middle name
Last name	Huang

Organization

Institute for Health Economics and Policy

Division name

Research Department

Zip code

1050001

Address

3F, Tokyu Toranomon Building, 1-21-19 Toranomon, Minato-ku, Tokyo, Japan

TEL

0335068529

Homepage URL

Email

shinetsu.ko@ihep.jp

Institute

Institute for Health Economics and Policy

Institute

Department

Personal name

Organization

Institute for Health Economics and Policy

Organization

Division

Category of Funding Organization

Non profit foundation

Nationality of Funding Organization

Co-sponsor

Name of secondary funder(s)

Organization

Institute for Health Economics and Policy

Address

3F, Tokyu Toranomon Building, 1-21-19 Toranomon, Minato-ku, Tokyo, Japan

Tel

0335068529

Email

info@ihep.jp

Secondary IDs

YES

Study ID_1

R6-005

Org. issuing International ID_1

Institute for Health Economics and Policy

Study ID_2

Org. issuing International ID_2

IND to MHLW

Institutions

Date of disclosure of the study information

2026

Year

09

Month

10

Day

URL releasing protocol

The protocol is not publicly available.

Publication of results

Unpublished

URL related to results and publications

not publicly available

Number of participants that the trial has enrolled

2000

Results

Analyses included 2,000 participants immediately after the intervention and 1,780 at two months. After adjustment for age, sex, education, household income, and baseline intention, none of the three interventions significantly affected participation intention or behaviour compared with control. In sex-stratified analyses, men receiving the loss-framed message had higher odds of immediate participation intention (adjusted OR 1.89, 95% CI 1.06-3.39, p=0.03). No significant effects were observed among women.

Results date posted

2026

Year

09

Month

10

Day

Results Delayed

Results Delay Reason

Date of the first journal publication of results

Baseline Characteristics

Participants were 2,000 adults aged 60 years or older residing in Japan, recruited from an online survey company's panel. None were certified as requiring support or long-term care under Japan's long-term care insurance system, and none were participating in community gathering places ("Kayoi-no-ba") at screening. There were 500 participants in each of the loss-framed, social-norm, precommitment, and control groups. Baseline assessments included age, sex, educational attainment, household income, and intention to participate in Kayoi-no-ba before the intervention.

Participant flow

Of 8,325 online panel members screened, 6,325 were excluded because they did not meet one or more eligibility criteria relating to age, residence, certification for support or long-term care, or current participation in Kayoi-no-ba. The remaining 2,000 eligible participants provided electronic informed consent and were randomly allocated in a 1:1:1:1 ratio to the loss-framed, social-norm, precommitment, or control group (500 participants per group).
Wave 1 was conducted on 8-9 July 2025, and all 2,000 participants were included in the analysis of participation intention immediately after the intervention. Wave 2 was conducted approximately two months later, on 8-9 September 2025, and 1,780 participants completed the follow-up survey (follow-up rate, 89.0%). A total of 220 participants did not complete follow-up. The analysis of self-reported participation included the 1,780 follow-up respondents.

Adverse events

The intervention consisted of a single online presentation of an informational message. Adverse events were not specified as an outcome measure, and no adverse event data were collected.

Outcome measures

1. Intention to participate in Kayoi-no-ba immediately after the intervention
Immediately after the intervention, participants reported their desired frequency of participation in community gathering places ("Kayoi-no-ba") using six response options: "four or more times per week," "two to three times per week," "once per week," "one to three times per month," "a few times per year," and "I do not want to participate."
2. Self-reported participation in Kayoi-no-ba approximately two months after the intervention
At follow-up approximately two months after the intervention, participants reported their participation frequency using six response options: "four or more times per week," "two to three times per week," "once per week," "one to three times per month," "less frequently," and "no participation."

Plan to share IPD

IPD sharing Plan description

Recruitment status

Completed

Date of protocol fixation

2025

Year

03

Month

10

Day

Date of IRB

2025

Year

03

Month

10

Day

Anticipated trial start date

2025

Year

07

Month

08

Day

Last follow-up date

2025

Year

09

Month

09

Day

Date of closure to data entry

2025

Year

09

Month

10

Day

Date trial data considered complete

2025

Year

10

Month

01

Day

Date analysis concluded

Other related information

Registered date

2026

Year

09

Month

10

Day

Last modified on

2026

Year

09

Month

10

Day

Link to view the page

Value
https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000071971