Ambient air temperatures in Mexico have broken record highs in 2024 with Hermosillo reaching the highest maximum temperature recorded in Mexico at 51.9 C. 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 can promote physical, mental and social wellbeing 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 northern zone of Mexico. To meet this goal, the investigators will conduct a cluster-randomized controlled trial to establish the effects of cool roof use on health, indoor environment and economic outcomes in Hermosillo, 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 Hermosillo (located in the State of Sonora, Mexico) are exposed to heat and low humidity year-round. The State of Sonora has a large burden of non-communicable diseases (NCDs), with nearly 28% of deaths due to NCDs, such as heart diseases and diabetes mellitus. The combined burden of heat and NCDs places Sonora's, especially Hermosillo'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 Hermosillo. The trial will quantify whether cool roofs are an effective passive home cooling intervention with beneficial health effects for vulnerable populations in Hermosillo. Findings will inform regional policy responses on scaling cool roof implementation to protect people from increasing heat exposure driven by climate change.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
DOUBLE
Enrollment
800
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.
Instituto Tecnológico de Hermosillo
Hermosillo, Sonora, Mexico
Resting heart rate
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.
Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Blood glucose control
Three month average of blood glucose in mmol/mol measured as glycosylated hemoglobin (HbA1c) using capillary blood and the HemoCue® HbA1c 501 System.
Time frame: Two measurements will be taken: one at baseline and one in the last month of three consecutive hottest months.
Depression
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.
Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Heat-related symptoms
Self-reported heat-related symptoms in the past month, assessed using a recall questionnaire.
Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Physician diagnosed heat-related illnesses
Self-reported new diagnosis from a medical practitioner of a heat-related illness in the last month assessed using a recall questionnaire.
Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Food insecurity
Self-reported experience based measure of individual food security assessed using the Food Insecurity Experience Scale (FIES).
Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Diet quality
Self-reported individual food group consumption in the previous 24 hours assessed using the Diet Quality Questionnaire (DQQ).
Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Health-related quality of life
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.
Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Indoor thermal comfort
Self-reported household heat, humidity and comfort experience over the last four weeks assessed using a recall questionnaire.
Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Coping ability
Self-reported coping strategies for high indoor temperatures assessed using a recall questionnaire.
Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Life satisfaction
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.
Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Healthcare provider utilization
Self-reported healthcare provider utilization in the past four weeks assessed using a recall questionnaire.
Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Hospitalization
Self-reported overnight hospital stay in the past four weeks assessed using a recall questionnaire.
Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Systolic Blood Pressure
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.
Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.
Diastolic Blood Pressure
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.
Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.
Cognition
Accuracy and response time to the four-choice Deary-Liewald Test measured using the CogniFit app-based assessment tool.
Time frame: Eight measurements: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Inner Ear Canal Temperature
Internal body temperature (℃) measured once using Braun digital ear thermometer.
Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.
Dehydration
Dehydration as indicated by urine specific gravity ≥1.020 measured as urine specific gravity using Siemens Multistix SG dipstick.
Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Sleep quality
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.
Time frame: Eight measurements: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Aggression
Self-reported personal aggresion assessed using the Buss-Perry Aggression Questionnaire-Ultra Short Form (BPAQ-ML).
Time frame: Eight measurements: one at baseline and seven over 12 months, covering three consecutive hottest months and four alternate months.
Productivity
Self-reported job absenteeism and presenteeism assessed using the Health and Work Performance Questionnaire Short Form (HPQ-SF).
Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.
Indoor air temperature
Indoor air temperature (℃) measured using Hobo MX1101 heat and humidity measurement device.
Time frame: Measurements at 15 minute intervals for 12 months.
Indoor relative humidity
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.
Time frame: Measurements at 15 minute intervals for 12 months.
Indoor heat index
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.
Time frame: Measurements at 15 minute intervals for 12 months.
Household energy expenditure
Self-reported household energy expenditure assessed using a recall questionnaire from the head of the household.
Time frame: Eight measurements will be taken: one at baseline and seven over 12 months, covering the three consecutive hottest months and four alternate months.
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