Extreme heat events pose a significant health threat in Canada, as demonstrated by the 2021 heat wave that claimed over 600 lives in Western Canada. Most heat-related deaths occur indoors and are preventable. Primary care providers (PCPs), who serve 88% of Canadians, are uniquely positioned to identify and support at-risk individuals. Heat Smart, in alignment with Heat Alert and Response Systems (HARS), aims to bridge the gap between primary care and public health to enhance community resilience and reduce health inequities related to extreme heat events.

This randomized control trial in Eastern Ontario will examine whether patients receiving tailored digital health messages from their family physician or nurse practitioner change their behaviour to protect themselves from extreme heat-related illness. The Heat Smart study will:

• Assess risk: Analyze electronic medical records and patient surveys to identify vulnerable individuals.
• Deliver tailored messages: Send personalized digital guidance via e-mail or text, offering heat safety advice and local resource information in English and French.
• Issue early warning alerts: Notify at-risk patients of upcoming heat events, prompting action.
• Evaluate impact: Use surveys and health data to measure effectiveness in reducing heat-related health impacts.

Short-term outcomes include increased awareness and preparedness among patients about heat-related health risks. Long-term goals involve scaling the intervention across Canada to reduce heat-related illnesses, enhance social connectedness, and decrease healthcare utilization.

Primary Hypothesis

The study will test the following primary hypothesis: "Patients who receive tailored digital health promotion messages from their primary care providers will perform more heat adaptive proactive behaviours to protect themselves from heat-related illness compared to those who do not receive such messages."

Secondary Hypotheses

1. Patients receiving Heat Smart messages will demonstrate greater engagement in specific heat preparedness activities, such as creating heat safety plans and forming networks among friends, neighbours, and relatives (patient survey data).
2. Patients in the intervention group will experience lower rates of heat-related healthcare utilization, as measured by primary care provider visits, emergency department visits and filling prescription drugs during heat events (ICES data).
3. The intervention will be effective across different socio-demographic subpopulations, including older adults, individuals with chronic illnesses, and socially isolated individuals.
4. The integration of primary care into HARS will enhance public health system coordination and improve response strategies for extreme heat events.

This study employs a cluster randomized controlled trial (RCT) to evaluate the impact of a heat adaptation digital messages intervention. Only primary care practices with at least 2 participating practitioners will be included in the study, where each PCP will act as a patient cluster. For each practice, the Primary Care Providers will be randomly assigned, and all their adult patient panel will either receive heat smart adaptation digital messages (the exposed group) or non-heat wave health promotion digital messages (the control group).

The study follows an intention-to-treat (ITT) design, meaning that all participants who consent to participate will be analyzed based on their original group assignment, regardless of adherence to the heat smart digital messages intervention (e.g., did the participant read the message). The study will have a two-year follow-up period to assess behavioural changes related to heat adaptation.

Research Objectives

The Heat Smart project aims to enhance primary care involvement in public health led heat adaptation strategies and improve the preparedness of at-risk populations for extreme heat events.

1. Assess Individual-Level Risks for Excessive Heat-Related Illnesses

   • Identify patients at increased risk of heat-related illness using primary care provider's electronic medical records and patient surveys.

   • Characterize socio-cultural, demographic, and clinical factors that contribute to heat vulnerability, including:

     • Age (older adults, children)
     • Chronic illnesses (e.g., cardiovascular disease, diabetes, asthma, mental health conditions)
     • Social isolation and poverty
     • Use of medications that impair thermoregulation

   • Segment patients into subpopulations based on shared characteristics to tailor interventions.

   • Assess patients' information needs and barriers to heat preparedness.

2. Implement and Evaluate a Digital Messaging Intervention

   • Deliver tailored, evidence-based digital messages (via email or text) to all adult patients of participating primary care providers to:

     • Educate them on heat-related health risks.
     • Encourage the development of personalized heat safety plans for patients at increased risk.
     • Provide information about local cooling stations, transportation options, and emergency resources.

   • Issue early warning alerts to at-risk patients when excessive heat events are imminent.

   • Evaluate the impact of the intervention through:

     • Patient surveys assessing self-reported behaviour change in heat preparedness.
     • Linking patient survey responses to health administrative data to measure healthcare utilization (e.g., emergency department visits, prescription medication use).

   • Determine the effectiveness of integrating primary care providers into public health-led Heat Alert and Response Systems (HARS).

3. Scale and Expand the Intervention

   • Refine and adapt the intervention based on rapid-cycle evaluations.
   • Expand to two additional provinces to test scaling feasibility.
   • Develop a national model for integrating primary care into climate adaptation strategies, ensuring scalability and sustainability.

4. Improve Health Equity and Climate Resilience

   • Target vulnerable and equity-deserving populations, ensuring that interventions are tailored to their needs.
   • Encourage social connectedness by fostering Check-in Companion heat response groups among friends, neighbours, and relatives.
   • Enhance collaboration between primary care and public health to create a cohesive, system-wide approach to adaptation to extreme heat events.
   • Provide policy-relevant insights to inform national heat adaptation strategies and reduce health inequities.

These objectives align with Canada's HeatADAPT Program and National Adaptation Strategy, ensuring a whole-of-society approach to protecting health during extreme heat events.

Randomization

• Patients will be assigned to intervention or control arms using cluster randomization. Block of sizes of 2 will be used to randomly assign the primary care provider to either the treatment or control arms, to ensure balance between groups and between practices.
• After randomization, balance across the two arms will be assessed using variables associated with vulnerability (e.g., age, sex, housing marginalization (ONT-Marg, based on 6-digit postal code) is included as a covariate to account for socio-economic disparities in vulnerability to heat-related events, neighbourhood rurality, self-reported baseline Heat Action Plan, chronic illness (e.g., cardiovascular disease, diabetes, asthma, mental health conditions) and heat susceptible diseases (e.g., requiring medications that impair thermoregulation)).

Inclusion Criteria:

The Heat Smart randomized controlled trial study will recruit patients and primary care providers (PCPs) from Eastern Ontario. The inclusion criteria ensure that the intervention reaches at-risk individuals while being scalable across different patient populations:

Primary Care Patients:

• Adults (18 years and older)
• Patients must be registered with a participating PCP.
• They must have had at least one visit with their PCP in the past two years to ensure active engagement.
• Participants must have an active email, cell phone or messaging service (SMS) to receive Heat Smart digital messages.
• Patients must be able to understand and consent to participate in the study.
• Patients must be able to communicate in at least one of the official languages (English, French).
• Participants will be recruited from PCP located in two Eastern Ontario public health districts: the Eastern Ontario Health Unit and Ottawa Public Health (including urban, rural, and Indigenous communities such as Akwesasne).

Primary Care Providers:

• Must be a licensed Family Physician (FP) or Nurse Practitioner (NP) in a practice of at least 2 PCPS.
• The providers must be offering comprehensive primary care to a panel of patients (not solely urgent care or walk-in services).
• Must work in a computerized primary care clinic with an electronic medical record system.
• Must expect to remain in practice for at least 24 months.
• Must be located in Eastern Ontario.
• Must be willing to use the Canadian Primary Care Information Network (CPIN) to deliver Heat Smart messages and surveys.
• Must be using Cliniconex or Qualtrics as a practice tool for communication enabling outreach before the patients are invited to consent to participate in the study.

Exclusion Criteria:

Patients who do not read French or English will be excluded from the study as they will not be able to give informed consent or to fill out the surveys. Patients who do not have an email address or text messaging service will be excluded for the same reason. Minors, patients with dementia and people who cannot read and write in English or French will not be eligible because the automated approach to surveying patients makes it impractical to properly obtain their consent.