Clinical Research Directory

Beat the Heat Boston

The goal of this stepped wedge trial is to assess the practical effects of air conditioners on hot weather impacts among older adults. The main questions it aims to answer are: How does the presence of an air conditioning unit affect heat stress, heat strain, mental health, and healthcare utilization among older adults who did not previously have access to air conditioning? How, and in what conditioners, do older adults use air conditioning once it is installed in their home? Researchers will compare participants in arms with (A) and without (B) air conditioning units in the first summer season; this will allow them to assess the effect of air conditioners. In the second summer season, both arms will have air conditioning units, but those in the year two distribution arm (B) will receive an electricity subsidy, while those in the year one AC distribution arm (A) will not, allowing researchers to assess the effect of an electricity subsidy. Participants will be randomized to receive an air conditioner and financial support for electricity costs in either the first summer season or the second summer season of the study. * Heat stress, heat strain, mental health, and healthcare utilization will be assessed via participant survey. * Air conditioner utilization will be assessed via continuous load monitoring devices. * Indoor air temperature will be assessed via continuous data loggers.

Identifying the Limits of Survivability in Heat-exposed Older Females

Climate change increases extreme heat events, elevating global heat-illness risk. Females have reduced heat loss capacity (\~5%) compared to males, driven by differences in skin blood flow and sweating responses. While findings on sex-mediated mortality are mixed, some studies suggest older females (≥65 years), face higher heat-related mortality/morbidity risks, evidenced by disproportionate female deaths in the 2021 Western Heat Dome. The effects of extreme uncompensable heat on older females remain understudied. Heat exposure initially causes net heat gain, raising core/skin temperatures and triggering heat-loss responses. Under compensable heat stress, heat loss balances gain, stabilizing core temperature. Uncompensable heat stress (exceeding maximal dissipation capacity) causes continuous core temperature rise, posing severe health risks. The specific temperature and relative humidity (RH) limits where compensability is lost are critical survival determinants, influenced by age and sex. Ramping protocols identify these limits: participants face progressively increasing heat stress (e.g., staged humidity rises) while core temperature is monitored. Core temperature typically stabilizes initially, then exhibits an abrupt rapid increase at an inflection point, operationally defined as the limit of compensability. Despite increasing use, ramping protocol validity for accurately identifying this threshold remains unverified. This project assesses ramping protocol validity for determining uncompensable conditions in older females and evaluates cumulative thermal and cardiovascular strain, as well as psychological and cognitive responses to both uncompensable and compensable heat. Participants will complete five trials. Trial 1 (Ramping): Rest at 42°C, 28% RH for 70min, then incremental RH increases (3% every 10min) to 70% RH. Individual core temperature (rectal) inflection points are identified from the ramping trial. Trials 2-5 (Fixed Conditions, Randomized): i) \~10% below inflection; ii) \~5% below inflection; iii) \~5% above inflection; iv) Thermo-neutral control (26°C, 45% RH). Comparing the rate of rectal temperature change and cumulative strain during prolonged fixed exposures (especially below vs. above inflection) will validate if the ramping inflection point represents the true limit of compensability for older females.

Assessing the Effectiveness of Heat Adaptation Digital Messages From Primary Care Providers to Their Patients on the Change in Behaviour for Heatwave-related Preparedness

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.

Heat Acclimation in Females

Heat acclimation is when you repeatedly exposure yourself to heat so that your body adapts and better tolerates heat. This project will determine if completing a heat acclimation maintenance period after heat acclimation is more beneficial than heat acclimating alone for exercise performance in the heat. To determine this, participants will exercise in the heat before heat acclimation, after heat acclimation, and after heat acclimation maintenance. Researchers will assess the heart's pumping capacity, blood volume, body temperature, and exercise performance to determine which approach is more effective.

Home-based Heat Therapy for Type 2 Diabetes

Insulin resistance and hyperglycemia predispose individuals with type 2 diabetes mellitus (T2DM) to endothelial dysfunction and a greater risk of cardiovascular diseases (CVD). Increased CVD risk in individuals with T2DM persists despite optimal pharmacological therapy, highlighting the need to identify complementary lifestyle interventions that improve cardiometabolic functions in this population. Evidence from animal models suggests that heat exposure improves metabolic functions. Notably, weekly heat exposure for 16 weeks blunts hyperinsulinemia and hyperglycemia induced by a high fat diet in mice. In parallel, studies in humans have shown that heat exposure improves vascular endothelial function. Based on such findings, it has been suggested that heat therapy may represent an effective lifestyle intervention to improve cardiometabolic functions. However, only 1 study has examined the impact of a heat therapy intervention on individuals with T2DM, demonstrating that 6 weeks of heat exposure reduces fasting plasma glucose and hemoglobin A1C. No study has considered potential vascular benefits of heat therapy in individuals with T2DM. This project will investigate cardiometabolic responses to repeated heat exposure in men and women with T2DM. We will test the hypothesis that 12 weeks of heat therapy improves postprandial fatty acid handling, insulin sensitivity and endothelial function in individuals with T2DM.

Postexercise Hot-Water Immersion on Exercise Performance in Hypoxia

The purpose of this study is to determine the effect of 5 days post-exercise hot water immersion on exercise performance at simulated altitude.

Mechanisms Underlying Hypoxic, Heat and Cross-tolerance Adaptation in Women

This study will consist of a parallel-groups design, with 30 healthy active female participants randomly assigned to either an experimental heat acclimation and exercise intervention, or a thermo-neutral exercise intervention control group. Interventions will be 10 days in duration, and consist of daily 60-minute exercise bouts under the appropriate environmental condition. Before and after each intervention, various tests will be conducted to establish exercise capacity under various environmental conditions, as well as underlying mechanisms of physiological adaptation induced by each intervention.

Preparing for Heat Waves - Enhancing Human Thermophysiological Resilience

As the ongoing progression of climate change exposes individuals to elevated temperatures and an escalating frequency of extreme heat events, the risk of more intense and prolonged heat waves raises significant concerns for public health, particularly among vulnerable populations. The physiological response to acute heat stress involves involuntary thermolytic reactions that may strain the cardiovascular system, especially in individuals with pre-existing vulnerabilities. Heat acclimation has been identified as a potential strategy to enhance thermoregulation and mitigate the adverse effects of heat stress. While existing research primarily focuses on athletes and military, this study aims to investigate the impact of a practical heat acclimation strategy, combining passive and active heat exposure, on thermophysiological, cardiovascular and metabolic parameters in healthy overweight adults. The study targets a population at increased risk for heat-related complications, seeking to provide realistic guidelines for broader application when a heat wave appears on the weather forecast.