Heart RateREFLECTNCT06831006
Assessing the Effect of Cool Roofs on Health Using Smartwatches in Colima, Mexico
A study testing Cool roof in people with Heart Rate and All-day Steps, run by University of Auckland, New Zealand at 1 site in Mexico.
Trial summary
Ambient air temperatures in Mexico have broken record highs in 2024. Solutions are needed to build heat resilience in communities and adapt to increasing heat from climate change. Sunlight-reflecting cool roof coatings may passively reduce indoor temperatures and energy use to protect home occupants from extreme heat. Read more about this study
- Who is it for?
- Ages 18 years and olderHealthy volunteers can take part
- Conditions the study is for
- Heart Rate, All-day Steps, Distance Walked
- What is being tested?
- Cool roof
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 800 participants
- Where
- 1 siteMexico
- Study dates
- 1 Apr 2026to 1 Sep 2027
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Permanent household resident
Who cannot join
- Roof damage, inaccessible or instability of roof adversely affecting cool roof coating application.
- Participant unable to provide written/verbal informed consent. Participants will be excluded if they are not willing or able to wear a smartwatch.
- Participants will be excluded if they do not have a smartphone with an internet connection that can connect to the smartwatch.
- Only one participant per household.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Mexico1 site
Universidad de Colima
Colima
Oliver Mendoza, +523121447489, oliver@ucol.mx
Oliver Mendoza
About this study
Official title: A Randomized Controlled Trial (RCT) Evaluating the Effects of Cool Roofs on Health Outcomes Using Smartwatches in Colima, Mexico
Ambient air temperatures in Mexico have broken record highs in 2024. Solutions are needed to build heat resilience in communities and adapt to increasing heat from climate change. Sunlight-reflecting cool roof coatings may passively reduce indoor temperatures and energy use to protect home occupants from extreme heat. Occupants living in poor housing conditions in the northern zone of Mexico are susceptible to increased heat exposure.
Heat exposure can instigate and worsen numerous physical, mental and social health conditions. The worst adverse health effects are experienced in communities that are least able to adapt to heat exposure. By reducing indoor temperatures, cool roof use may promote heart health, sleep and physical activity in household occupants.
The long-term research goal of the investigators is to identify viable passive housing adaptation technologies with proven health benefits to reduce the burden of heat stress in communities affected by heat in Mexico. To meet this goal, the investigators will conduct a randomized controlled trial to establish the effects of cool roof use on heart rate, sleep and physical activity in Colima, Mexico.
Read the detailed description
Increasing heat exposure from climate change is causing and exacerbating heat-related illnesses in millions worldwide - particularly in low-resource settings. June 2024 was the 13th consecutive hottest month on record globally - shattering previous records. Heat exposure can instigate and worsen health conditions, including cardiovascular, metabolic, endocrine and respiratory disease, heat-related illnesses, pregnancy complications, and mental health conditions. Adaptation is essential for protecting people from increasing heat exposure. The built environment, especially homes, is ideal for deploying interventions to reduce heat exposure and accelerate adaptation efforts. However, there currently is a lack of evidence on a global scale - generated through empirical studies - guiding the uptake of interventions to reduce heat stress in low-resource settings.
Cities and towns of LMIC are among the most vulnerable to the adverse impacts of climate change and are likely to experience increases in ambient air temperature over the coming decades. People in Colima are exposed to heat and low humidity year-round. The combined burden of heat and NCDs places Colima's population at greater risk of adverse health effects from heat extremes.
Sunlight-reflecting cool roof coatings passively reduce indoor temperatures and lower energy use, offering protection to home occupants from extreme heat. The investigators therefore aim to conduct a randomized controlled trial investigating the effects of cool roofs on heart rate, sleep and physical activity using smartwatches in Colima.
The trial will quantify whether cool roofs are an effective passive home cooling intervention with beneficial health effects for vulnerable populations in Colima. Findings will inform regional and global policy responses on scaling cool roof implementation to protect people from increasing heat exposure driven by climate change.
- Conditions
- Heart Rate, All-day Steps, Distance Walked, Active Minutes, Moderate-intensity Activity Minutes, Vigorous-intensity Activity Duration
- Being tested
- Cool roof
- Keywords
- Hot Temperature, Humidity, Housing, Wearable, Smartwatch, Heart rate, Cardiovascular, Physical activity, Sleep, Cool roof, Heat stress
- Medical subject headings
- Motor Activity, Heat Stress Disorders
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Cool roofOther
Cool roofs are a heat-reflecting material that can be applied to existing household roofing in the form of a liquid-applied membrane. Cool roofs work by increasing solar reflectance (the ability to reflect the visible wavelengths of sunlight, reducing heat transfer to the surface) and thermal emittance (the ability to radiate absorbed solar energy) thereby reducing the amount of heat transferred into the home.
| Study group | Role | What they receive |
|---|---|---|
| Cool roof | Experimental | Households will receive sunlight reflecting 'cool roof' coating on their roofs. Receives: Other: Cool roof |
| No cool roof | No intervention | No cool roof application. Households will keep their original roofing for the duration of the trial. |
What is being measured
The primary outcome is the main question the study is designed to answer.
Heart rate
Heart rate in beats per minute measured at 15-second intervals using Garmin Vivosmart 5 devices.
Measured: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Secondary outcomes (9)
All-day steps
The number of steps measured daily using Garmin Vivosmart 5 devices.
Measured: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Active minutes
The total number of minutes of active exercise daily using Garmin Vivosmart 5 devices.
Measured: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Distance walked
The total distance walked daily using Garmin Vivosmart 5 devices.
Measured: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Moderate-intensity activity minutes
The total number of minutes of moderate-intensity activity daily using Garmin Vivosmart 5 devices.
Measured: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at barements will be taken continuously for 12 months. Participants will be asked to wear their smartwatch for at least two weeks every month.
Vigorous-intensity activity duration
The total number of minutes of vigorous-intensity activity daily using Garmin Vivosmart 5 devices.
Measured: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Sleep quantity
The number of hours spent asleep each night using Garmin Vivosmart 5 devices.
Measured: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Time in sleep stages
The number of hours spent in sleep stages each night using Garmin Vivosmart 5 devices.
Measured: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Awake duration
The number of hours spent awake during sleep time each night using Garmin Vivosmart 5 devices.
Measured: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Sleep score
The Garmin sleep score (0-100) each night using Garmin Vivosmart 5 devices. A higher score means a better outcome.
Measured: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted17 Feb 2025
- Study start1 Apr 2026 (estimated)
- Primary completion1 Sep 2027 (estimated)
- Study completion1 Sep 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Heart RateStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Double blind
- Who is masked
- Investigator, Outcomes assessor
- Enrolment
- 800 participants (estimated)
Sponsor and investigators
- Lead sponsor
- University of Auckland, New Zealand
- Sponsor type
- University, hospital or other
- Collaborators
- Heidelberg University, London School of Hygiene and Tropical Medicine, Rutgers University, Labfront, Wellcome Trust, EPS, Universidad de Colima
- Responsible party
- Principal investigator, Aditi Bunker, University of Auckland, New Zealand
- Investigators
- Collin Tukuitonga, Sir. Dr., Principal investigator, University of Auckland, New Zealand
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06831006
- Sponsor's protocol ID
- 3728165
- Other IDs
- 226745/Z/22/Z
- Acronym
- REFLECT
- Status last verified
- Mar 2026
- First submitted
- 13 Feb 2025
- Last updated
- 11 Mar 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes: Data that can be shared unconditionally underpinning the published research articles will be made available to other researchers at the time of publication, and data will be linked via the article DOI. Data that cannot be unconditionally shared upon publication owing to confidentiality or data protection requirements will be identified as such and a contact email will be provided in relevant publications for data access enquiries by other researchers. Individual names of study participants and identifying factors will be removed prior to data sharing. It is expected that demographic data of people at the study sites (family size and composition, basic socioeconomic indicators) may contain personally identifiable information and location data. All such data will be removed prior to storage on online data repositories and therefore will be available to be publicly shared at the time of publication of manuscripts.
Study at a glance
From the registry record, last updated by the sponsor on 11 Mar 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Randomized Controlled Trial (RCT) Evaluating the Effects of Cool Roofs on Health Outcomes Using Smartwatches in Colima, Mexico
- ClinicalTrials.gov ID
- NCT06831006
- Acronym / sponsor ID
- REFLECT / 3728165
- Conditions
- Heart Rate, All-day Steps, Distance Walked, Active Minutes, Moderate-intensity Activity Minutes, Vigorous-intensity Activity Duration
- Keywords
- Hot Temperature, Humidity, Housing, Wearable, Smartwatch, Heart rate, Cardiovascular, Physical activity
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 800 participants (estimated)
- Lead sponsor
- University of Auckland, New ZealandUniversity, hospital or other
- Collaborators
- Heidelberg University, London School of Hygiene and Tropical Medicine, Rutgers University, Labfront, Wellcome Trust, EPS, Universidad de Colima
- Study start
- 1 Apr 2026 (estimated)
- Primary completion
- 1 Sep 2027 (estimated)
- Study completion
- 1 Sep 2027 (estimated)
- First posted
- 17 Feb 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Ambient air temperatures in Mexico have broken record highs in 2024. Solutions are needed to build heat resilience in communities and adapt to increasing heat from climate change. Sunlight-reflecting cool roof coatings may passively reduce indoor temperatures and energy use to protect home occupants from extreme heat. Occupants living in poor housing conditions in the northern zone of Mexico are susceptible to increased heat exposure.
Heat exposure can instigate and worsen numerous physical, mental and social health conditions. The worst adverse health effects are experienced in communities that are least able to adapt to heat exposure. By reducing indoor temperatures, cool roof use may promote heart health, sleep and physical activity in household occupants.
The long-term research goal of the investigators is to identify viable passive housing adaptation technologies with proven health benefits to reduce the burden of heat stress in communities affected by heat in Mexico. To meet this goal, the investigators will conduct a randomized controlled trial to establish the effects of cool roof use on heart rate, sleep and physical activity in Colima, Mexico.
Detailed description
Increasing heat exposure from climate change is causing and exacerbating heat-related illnesses in millions worldwide - particularly in low-resource settings. June 2024 was the 13th consecutive hottest month on record globally - shattering previous records. Heat exposure can instigate and worsen health conditions, including cardiovascular, metabolic, endocrine and respiratory disease, heat-related illnesses, pregnancy complications, and mental health conditions. Adaptation is essential for protecting people from increasing heat exposure. The built environment, especially homes, is ideal for deploying interventions to reduce heat exposure and accelerate adaptation efforts. However, there currently is a lack of evidence on a global scale - generated through empirical studies - guiding the uptake of interventions to reduce heat stress in low-resource settings.
Cities and towns of LMIC are among the most vulnerable to the adverse impacts of climate change and are likely to experience increases in ambient air temperature over the coming decades. People in Colima are exposed to heat and low humidity year-round. The combined burden of heat and NCDs places Colima's population at greater risk of adverse health effects from heat extremes.
Sunlight-reflecting cool roof coatings passively reduce indoor temperatures and lower energy use, offering protection to home occupants from extreme heat. The investigators therefore aim to conduct a randomized controlled trial investigating the effects of cool roofs on heart rate, sleep and physical activity using smartwatches in Colima.
The trial will quantify whether cool roofs are an effective passive home cooling intervention with beneficial health effects for vulnerable populations in Colima. Findings will inform regional and global policy responses on scaling cool roof implementation to protect people from increasing heat exposure driven by climate change.
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Double blind (investigator, outcomes assessor)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Cool roof | Experimental | Other: Cool roofHouseholds will receive sunlight reflecting 'cool roof' coating on their roofs. |
| No cool roof | No intervention | –No cool roof application. Households will keep their original roofing for the duration of the trial. |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (1 listed)
- Permanent household resident
Key exclusion criteria (4 listed)
- Roof damage, inaccessible or instability of roof adversely affecting cool roof coating application.
- Participant unable to provide written/verbal informed consent. Participants will be excluded if they are not willing or able to wear a smartwatch.
- Participants will be excluded if they do not have a smartphone with an internet connection that can connect to the smartwatch.
- Only one participant per household.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Cool roofCool roofs are a heat-reflecting material that can be applied to existing household roofing in the form of a liquid-applied membrane. Cool roofs work by increasing solar reflectance (the ability to reflect the visible wavelengths of sunlight, reducing heat transfer to the surface) and thermal emittance (the ability to radiate absorbed solar energy) thereby reducing the amount of heat transferred into the home. | Other | Cool roof |
Primary outcome
Heart rate
Time frame: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Heart rate in beats per minute measured at 15-second intervals using Garmin Vivosmart 5 devices.
9 secondary outcomes
All-day steps
Time frame: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Active minutes
Time frame: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Distance walked
Time frame: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Moderate-intensity activity minutes
Time frame: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at barements will be taken continuously for 12 months. Participants will be asked to wear their smartwatch for at least two weeks every month.
Vigorous-intensity activity duration
Time frame: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Sleep quantity
Time frame: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Time in sleep stages
Time frame: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Awake duration
Time frame: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Sleep score
Time frame: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 11 Mar 2026.
- Individual participant dataSharing planned: Yes. Data that can be shared unconditionally underpinning the published research articles will be made available to other researchers at the time of publication, and data will be linked via the article DOI. Data that cannot be unconditionally shared upon publication owing to confidentiality or data protection requirements will be identified as such and a contact email will be provided in relevant publications for data access enquiries by other researchers. Individual names of study participants and identifying factors will be removed prior to data sharing. It is expected that demographic data of people at the study sites (family size and composition, basic socioeconomic indicators) may contain personally identifiable information and location data. All such data will be removed prior to storage on online data repositories and therefore will be available to be publicly shared at the time of publication of manuscripts.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Collin Tukuitonga, Sir. Dr. principal investigator
University of Auckland, New Zealand
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Cool roof in people with Heart Rate and All-day Steps, run by University of Auckland, New Zealand at 1 site in Mexico.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 1 inclusion and 4 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 11 Mar 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Mexico. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Aditi Bunker, Dr (+49 6221 565344, aditi.bunker@uni-heidelberg.de), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Heart rate (time frame: Smartwatches will be worn for two consecutive weeks per month. Eight measurement points will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 11 Mar 2026.