Assessing the Effect of Cool Roofs on Health Using Smartwatches (REFLECT)

A Randomized Controlled Trial (RCT) Evaluating the Effects of Cool Roofs on Health Outcomes Using Smartwatches: a Global Multi-center Study

Ambient air temperatures in Asian, Latin American, African, and Pacific climate hotspots 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 globally - for example in informal settlements, slums, and low-socioeconomic households - 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 application may improve heart health, sleep and physical activity in household occupants.

The long-term research goal is to identify viable passive housing adaptation technologies with proven health benefits to reduce the burden of heat stress in communities affected by heat globally. To meet this goal, the investigators will use smartwatches to measure the effects cool roof application on heart health, sleep and physical activity in four urban climate hotspots: Ouagadougou, Burkina Faso; Hermosillo, Mexico; Ahmedabad, India; and Niue, Oceania.

Study Overview

• Status: Active, not recruiting
• Conditions: Heart Rate; Sleep Quantity; All-day Steps; Distance Walked; Active Minutes; Moderate-intensity Activity Minutes; Vigorous-intensity Activity Duration; Time in Sleep Stages; Awake Duration; Sleep Score
• Intervention / Treatment: Other: Cool roof

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 numerous health conditions. Adaptation is essential for protecting people from increasing heat exposure. The built environment, especially homes, are ideal for deploying interventions to reduce heat exposure and accelerate adaptation efforts. However, evidence is currently lacking on a global scale - generated through empirical studies - guiding the uptake of interventions to reduce indoor heat stress in low resource settings.

Sunlight-reflecting cool roof coatings passively reduce indoor temperatures and lower energy use, offering protection to home occupants from extreme heat. Continuous monitoring of health and wellbeing using smartwatches can provide insight into important parameters such as heart rate, sleep and physical activity - which are all affected by heat. Using smartwatches, the investigators will also continuously measure health and wellbeing outcomes during the day and night. The investigators will conduct a global multi-centre study to investigate the effects of cool-roof use on heart rate, sleep and physical activity in four urban climate hotspots - Ouagadougou, Burkina Faso (sub-Saharan Africa), Ahmedabad, India (Asia), Niue (Oceania), and Sonora, Mexico (Latin America). These sites represent hotspots where people experience a triple burden from heat exposure, chronic health issues and vulnerable housing conditions (slums, informal settlements and low socioeconomic housing). They also exhibit diversity in climate profiles, housing typology, level of socioeconomic development, population density and rates of urbanisation.

This trial will quantify whether cool roofs are an effective passive home cooling intervention with beneficial health effects for vulnerable populations in four locations. Findings will inform global policy responses on scaling cool roof implementation to protect people from increasing heat exposure driven by climate change.

• Study Type: Interventional
• Enrollment (Estimated): 800
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Burkina Faso
  • Ouagadougou, Burkina Faso
    • University Joseph Ki-Zerbo
• India
  • Gandhinagar
    • Ahmedabad, Gandhinagar, India
      • Indian Institute of Public Health Gandhinagar
• Mexico
  • Sanora
    • Hermosillo, Sanora, Mexico
      • Instituto Tecnológico de Hermosillo
• Niue
  • Alofi, Niue
    • Niue

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• Permanent household resident

Exclusion Criteria:

• 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.
• In Mexico and Niue, 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.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Cool roof; Households will receive sunlight reflecting 'cool roof' coating on their roofs.	Other: Cool roof; Cool roofs are a sunlight reflecting roof coating that can reduce indoor temperature. Cool roofs have high solar reflectance (reflecting the ultraviolet and visible wavelengths of sunlight, reducing heat transfer to the surface of a roof) and high thermal emittance (radiating absorbed solar energy).
No Intervention: No cool roof; No cool roof application. Households will keep their original roofing for the duration of the trial.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Heart rate	Heart rate in beats per minute measured at 15-second intervals using Garmin Vivosmart 5 devices.	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 Outcome Measures

Outcome Measure	Measure Description	Time Frame
All-day steps	The number of steps measured daily using Garmin Vivosmart 5 devices.	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.	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.	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.	MeasuSmartwatches 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.	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.	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.	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.	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.	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.

Collaborators and Investigators

• Sponsor: Aditi Bunker
• Collaborators: London School of Hygiene and Tropical Medicine; Boston University; Heidelberg University; Rutgers University; University of Ouagadougou, Burkina Faso; Pacific Community; Indian Institute of Public Health, India; Labfront; Resene; Habitat for Humanity; The Tindall Foundation; Sika Services AG; SOPREMA; Engineered Polymer Solutions (EPS B.V.); Instituto Tecnológico de Hermosillo

Study record dates

Study Major Dates

• Study Start (Actual): September 4, 2024
• Primary Completion (Estimated): September 1, 2027
• Study Completion (Estimated): September 1, 2027

Study Registration Dates

• First Submitted: August 28, 2024
• First Submitted That Met QC Criteria: August 28, 2024
• First Posted (Actual): August 30, 2024

Study Record Updates

• Last Update Posted (Actual): February 27, 2026
• Last Update Submitted That Met QC Criteria: February 25, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: Sleep; Physical activity; Cardiovascular; Smartwatch; Heart rate; Wearable; Housing; Heat stress; Humidity; Hot Temperature; Cool roof
• Additional Relevant MeSH Terms: Wounds and Injuries; Behavior; Heat Stress Disorders; Motor Activity
• Other Study ID Numbers: 3728163; 226745/Z/22/Z (Other Grant/Funding Number: Wellcome Trust UK)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES

IPD Plan Description

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.

• IPD Sharing Time Frame: At the time of publication.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF; CSR

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No