ANZCTR - Registration

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Trial registered on ANZCTR

Registration number

ACTRN12626001234303

Ethics application status

Approved

Date submitted

7/09/2026

Date registered

12/10/2026

Date last updated

12/10/2026

Date data sharing statement initially provided

12/10/2026

Type of registration

Prospectively registered

Titles & IDs

Public title

SMS-Text messaging for heat adaptation behaviours for Australians with chronic health conditions

Scientific title

A randomised controlled trial of a tailored text message intervention for heat adaptation in adult Australians: Heat Outcome Trial (HOT) TEXT

Additional trial identifiers [1]

Nil

Universal Trial Number (UTN)

Trial acronym

Related trial records

Health condition

Health condition(s) studied:

cardiovascular disease

respiratory disease

renal disease

metabolic disease

Condition category

Condition code

Cardiovascular

Coronary heart disease

Cardiovascular

Hypertension

Metabolic and Endocrine

Diabetes

Renal and Urogenital

Kidney disease

Respiratory

Asthma

Respiratory

Chronic obstructive pulmonary disease

Public Health

Health promotion/education

Public Health

Health service research

Intervention/exposure

Study type

Interventional

Description of the intervention or exposure

Intervention Background: Currently, generic heat warnings are the standard of care in public health notifications. However, such communication may lack efficiency, fail to reach the target population, or may lead to suboptimal behaviour change if it isn't timely, accessible, consistent or considered trustworthy. We completed an earlier proof-of-concept (pilot study) of a text messaging intervention, to assess tailored SMS warnings for acceptability and feasibility. Participants indicated that targeted messaging via SMS was both feasible and acceptable and engagement with message guidance was strong amongst all participants in the intervention arm. The current study is a large-scale randomised controlled trial (RCT) using an SMS-based messaging intervention providing disease-specific messages to adults with chronic conditions (such as cardiovascular disease, respiratory disease, kidney disease).

Who: The research team, comprising investigators with expertise spanning information technology, climate and health, clinical care, consumer engagement, and research design, will deliver the intervention. Clinicians will inform the tailored text message content.

Delivery: Trial participants will be randomly assigned to one of two arms:
Control arm - this group will be receiving general information via text message (SMS) on managing heat;
Intervention arm - this group will be receiving tailored, disease- and location-specific advice messages via text (Short Message Service -SMS). Message length is estimated to be approximately 150 words or less, and and will be one-way interactions i.e., participants will not be required to provide a response. The intervention will be triggered by a rule-based algorithm using both Bureau of Meteorology (BOM) heat alert data, and participant (demographic, vulnerabilities, health status) data. Messages will be selected and tailored according to a message library developed by the research team (and informed by expert clinicians). Messages will be text-based and contain menu response options for accessing additional information e.g., health management actions. An example of tailoring may be: "Hi [Name], This is an extreme heat warning in [Location] from [Date] to [Date]. You are at higher risk [moderate to very high risk]of heat illness due to [health condition, medication X etc.]. [Action 1] is advised by [Time e.g., 9am], [Action 2e.g.. drink more water than usual even if you're not feeling thirsty]. [Action 3]. For more information[Response menu options]. Call 000 if you experience [Symptoms]."

Mode of delivery: Survey data will be collected via the REDCap platform. Our experienced software development team will employ commercial off-the-shelf (COTS) technology platforms which will integrate participant data and weather data (from the Bureau of Meteorology) including heatwave warning data, to tailor messages. The virtual intervention will issue text messages facilitated though Amazon Web Services. MS Teams teleconferencing platform will be used for the Focus Group interviews.

Frequency of intervention: text message intervention will be delivered up to two days prior (or upon availability of the forecast) to forecasted heat event, followed by a text message one day prior to the event.

Intervention location: This study will be conducted online at participants’ preferred location (e.g., place of residence) across Australia (including all states and territories).

Monitoring: We will be conducting post-intervention surveys at 3-days and 7-days post-trial.

Intervention code [1]

Prevention

Intervention code [2]

Lifestyle

Intervention code [3]

Behaviour

Description of the comparator or control

Participants will receive general information on managing heat prior to an extreme heat event via SMS. Message length is estimated to be approximately 100 words or less. Message content will contain weather data about an upcoming heatwave event and general health advice about staying cool during extreme temperatures.

Control group

Active

Outcomes

Primary outcome [1]

Changes in heat-related symptoms

Timepoint [1]

Baseline (at enrolment, pre-heatwave and before text-messaging); 3 days post-heatwave event

Secondary outcome [1]

Changes in heat-adaptive behaviours

Timepoint [1]

3-days post-heatwave event

Secondary outcome [2]

Changes in acute care utilisation

Timepoint [2]

Baseline (at enrolment, prior to the heatwave period); 3-day post heatwave event

Secondary outcome [3]

Messaging intervention usability

Timepoint [3]

4-days and 7-days post-intervention

Eligibility

Key inclusion criteria

Adults 18 years+ residing in Australia
Participants with chronic conditions (for example, cardiovascular, respiratory or kidney diseases) will be recruited. Participants will meet the following eligibility criteria:
Adults aged 18 years and older residing in Australia
Any sex, ethnicity and medical background
Possess a mobile phone and an Australian number
Able to read and communicate in English
Willingness to provide informed consent and to participate and comply with study requirements

Minimum age

18 Years

Maximum age

No limit

Sex

Both males and females

Healthy volunteers

Key exclusion criteria

Individuals younger than 18 yrs (children)
Individuals not residing in Australia
Residing in nursing home or aged care facilities
Participation in another risk communication trial for heat adaptation at time of study

Study design

Purpose of the study

Prevention

Allocation to intervention

Randomised controlled trial

Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)

Central randomisation will be performed by an independent team member (statistician) to maintain allocation concealment until enrolment. The trial will be double-blind (participants and researchers).

Methods used to generate the sequence in which subjects will be randomised (sequence generation)

Simple randomisation: Computer-based random number generation

Masking / blinding

Blinded (masking used)

Who is / are masked / blinded?

The people receiving the treatment/s

The people analysing the results/data

Intervention assignment

Parallel

Other design features

Phase

Not Applicable

Type of endpoint/s

Efficacy

Statistical methods / analysis

5566 adult Australians. We calculate sample size based on the primary outcome of self-reported heat symptoms. According to a sample of 499 older Australians, up to 20% reported experiencing some heat symptoms [1]. Several meta-analyses show that tailored text message interventions can have large to moderate effect sizes from 54% to 32% [2, 3] in improving outcomes such as smoking cessation, physical activity, and medication adherence. To remain conservative, we propose the trial would result in a relatively small effect size of 25% (Relative Risk of 1.25), which means that 15% of participants in the intervention group will experience self-diagnosed heat symptoms, compared to 20% in the control group. A total sample of 5566 participants is required to detect this difference, with 80% power and a two-sided significance level of 0.05 [4]. This calculation has also factored in a study dropout rate of 25% and a further 60% possibility of participants not being exposed to heatwaves (based on a heuristic assessment of historic patterns).

References:
[1] Nitschke M, Hansen A, Bi P, Pisaniello D, Newbury J, Kitson A, et al. Risk Factors, Health Effects and Behaviour in Older People during Extreme Heat: A Survey in South Australia. International Journal of Environmental Research and Public Health [Internet]. 2013; 10(12):[6721-33 pp.]
[2] Head KJ, et al. Efficacy of text messaging-based interventions. Soc Sci Med. 2013;97:41-8.
[3] Sahin C, et al. Tailored mobile text messaging interventions. Digit Health. 2019;5.
[4] Noordzij M, et al. Sample size calculations. Nephrol Dial Transplant. 2010;25(5):1388-93.

Recruitment

Recruitment status

Not yet recruiting

Date of first participant enrolment

Anticipated

12/10/2026

Actual

Date of last participant enrolment

Anticipated

30/11/2026

Actual

Date of last data collection

Anticipated

31/03/2027

Actual

Sample size

Target

5566

Accrual to date

Final

Recruitment in Australia

Recruitment state(s)

ACT,NSW,NT,QLD,SA,TAS,WA,VIC

Funding & Sponsors

Funding source category [1]

University

Name [1]

Macquarie University

Address [1]

Country [1]

Australia

Primary sponsor type

University

Name

Macquarie University

Address

Country

Australia

Secondary sponsor category [1]

None

Name [1]

Address [1]

Country [1]

Ethics approval

Ethics application status

Approved

Ethics committee name [1]

Macquarie University Human Research Ethics Committee Medical Sciences

Ethics committee address [1]

https://www.mq.edu.au/research/ethics-integrity-and-policies/ethics/human-ethics

Ethics committee country [1]

Australia

Date submitted for ethics approval [1]

20/02/2025

Approval date [1]

14/04/2025

Ethics approval number [1]

Summary

Brief summary

Extreme weather events attributable to climate change are occurring with increasing frequency and intensity. Whilst extreme temperatures can affect people of all ages and health status, certain populations are more vulnerable, especially older adults and those who have pre-existing chronic conditions such as cardiovascular diseases. Vulnerable populations are more sensitive to heat-related health risks and are more likely to suffer morbidity and mortality associated with heatwave exposure. As population exposure to extreme heat rises and our population ages, the associated health burden will continue to grow.
The trial purpose is to evaluate whether a tailored text messaging intervention can reduce patient-reported heat symptoms, increase adoption of heat adaptive behaviours and reduce utilisation of health services during and after extreme heat days for Australian adults living with chronic conditions.

Trial website

Trial related presentations / publications

Public notes

Contacts

Principal investigator

Name

Prof Enrico Coiera

Address

Level 6, 75 Talavera Rd, Macquarie University, 2109, NSW

Country

Australia

Phone

+61 2 9850 2403

Fax

[email protected]

Contact person for public queries

Name

Dr Hania Rahimi Ardabili

Address

Level 6, 75 Talavera Rd, Macquarie University, 2109, NSW

Country

Australia

Phone

+61 2 9850 9419

Fax

[email protected]

Contact person for scientific queries

Name

Enrico Coiera

Address

Level 6, 75 Talavera Rd, Macquarie University, 2109, NSW

Country

Australia

Phone

+61 2 9850 2403

Fax

[email protected]

Data sharing statement

Will the study consider sharing individual participant data?

Yes

Will there be any conditions when requesting access to individual participant data?

Persons/groups eligible to request access:
• Researchers
Conditions for requesting access:
• Yes, conditions apply:
• Requires review on a case-by-case basis by the trial custodian, sponsor or data sharing committee
• Requires a scientifically sound proposal or protocol
• Requires approval by an ethics committee
• Requires a data sharing agreement between data requester and trial custodian or sponsor

What individual participant data might be shared?

• De-identified individual participant data:
• All outcomes data
• Published results
• Primary outcome(s)

What types of analyses could be done with individual participant data?

• Systematic reviews and meta-analyses
• Studies exploring new research questions

When can requests for individual participant data be made (start and end dates)?

From:
After publication of main results
To:
A finite period of: 15 years

Where can requests to access individual participant data be made, or data be obtained directly?

• Email of trial custodian, sponsor or committee: [email protected]

Are there extra considerations when requesting access to individual participant data?

What supporting documents are/will be available?

Type	Citation	Link	Email	Other Details	Attachment
Ethical approval					Approval Letter_15_04_2025.pdf

Results publications and other study-related documents

Documents added manually

No documents have been uploaded by study researchers.

Documents added automatically

No additional documents have been identified.

Trial Review

Documents added manually

Documents added automatically