Assessing the Effects of Cool Roofs on Indoor Environments and Health in Colima, Mexico

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, are 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, populations 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 cluster-randomized controlled trial investigating the effects of cool-roof use on health, environmental and economic outcomes 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 policy responses on scaling cool roof implementation to protect people from increasing heat exposure driven by climate change.

• Cool roof (Other): 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.

Primary outcomes

• Resting heart rate [Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.]: Resting heart rate in beats per minute measured as the average of three readings in the left arm over one hour using portable automated sphygmomanometers.
• Blood glucose control [Two measurements will be taken: one at baseline and one in the last month of three consecutive hottest months.]: Three month average of blood glucose in mmol/mol measured as glycosylated hemoglobin (HbA1c) using capillary blood and the HemoCue® HbA1c 501 System.
• Depression [Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.]: Self-reported presence and frequency of symptoms of depression assessed using aggregate score of the Patient Health Questionnaire 9 (PHQ-9). Minimum score of 0 and a maximum score of 27 with a higher score meaning a worse outcome.

Secondary outcomes

• Heat-related symptoms [Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.]: Self-reported heat-related symptoms in the past month, assessed using a recall questionnaire.
• Physician diagnosed heat-related illnesses [Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.]: Self-reported new diagnosis from a medical practitioner of a heat-related illness in the last month assessed using a recall questionnaire.
• Food insecurity [Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.]: Self-reported experience based measure of individual food security assessed using the Food Insecurity Experience Scale (FIES).
• Diet quality [Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.]: Self-reported individual food group consumption in the previous 24 hours assessed using the Diet Quality Questionnaire (DQQ).
• Health-related quality of life [Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.]: Current self-reported health-related quality of life assessed using the EuroQol EQ-5D-5L quality assessment tool. The minimum and maximum scores for the EuroQol EQ-5D-5L quality assessment tool are -0.59 and 1, respectively. A score of 1 represents the best possible health state, while scores below 0 indicate health states that are considered worse than death.
• Indoor thermal comfort [Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.]: Self-reported household heat, humidity and comfort experience over the last four weeks assessed using a recall questionnaire.
• Coping ability [Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.]: Self-reported coping strategies for high indoor temperatures assessed using a recall questionnaire.
• Life satisfaction [Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.]: Current self-reported life satisfaction assessed using the World Values Survey. Values can range from 1 to 10 with a higher score representing greater life satisfaction.
• Healthcare provider utilization [Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.]: Self-reported healthcare provider utilization in the past four weeks assessed using a recall questionnaire.
• Hospitalization [Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.]: Self-reported overnight hospital stay in the past four weeks assessed using a recall questionnaire.
• Systolic Blood Pressure [Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.]: Maximum blood pressure (mmHg) during systole measured as the average of three readings in the left arm over one hour using Blip portable automated sphygmomanometers.
• Diastolic Blood Pressure [Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.]: Minimum blood pressure (mmHg) during diastole measured as the average of three readings in the left arm over one hour using Blip portable automated sphygmomanometers.
• Cognition [Eight measurements: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.]: Accuracy and response time to the four-choice Deary-Liewald Test measured using the CogniFit app-based assessment tool.
• Inner Ear Canal Temperature [Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.]: Internal body temperature (℃) measured once using Braun digital ear thermometer.
• Dehydration [Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.]: Dehydration as indicated by urine specific gravity ≥1.020 measured as urine specific gravity using Siemens Multistix SG dipstick.
• Sleep quality [Eight measurements: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.]: Self-reported sleep distrubance assessed using the Athens Insomnia Scale (AIS). Values range from 0 to 24 with a higher score indicating a worse outcome.
• Aggression [Eight measurements: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.]: Self-reported personal aggresion assessed using the Buss-Perry Aggression Questionnaire-Ultra Short Form (BPAQ-ML).
• Productivity [Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.]: Self-reported job absenteeism and presenteeism assessed using the Health and Work Performance Questionnaire Short Form (HPQ-SF).
• Indoor air temperature [Measurements at 15 minute intervals for 12 months.]: Indoor air temperature (℃) measured using Hobo MX1101 heat and humidity measurement device.
• Indoor relative humidity [Measurements at 15 minute intervals for 12 months.]: Ratio of the amount of water vapor present in the air to the greatest amount possible at the same temperature (%) measured using Hobo MX1101 heat and humidity measurement device.
• Indoor heat index [Measurements at 15 minute intervals for 12 months.]: Index that combines air temperature and relative humidity (℃) based on temperature and humidity measurements from the Hobo MX1101 heat and humidity measurement device calculated using the formulae endorsed by the US National Oceanic and Atmospheric Administration.
• Household energy expenditure [Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.]: Self-reported household energy expenditure assessed using a recall questionnaire from the head of the household.

Sex: All, ages: 18 Years to any, accepts healthy volunteers

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.

• Collin Tukuitonga, Sir. Dr., Principal investigator, University of Auckland, New Zealand