Protective Cooling Measures to Safeguard Elderly People From Dangerous Summer Heat
- Conditions
- HyperthermiaHypertensionHeat StressHeat; WeatherAgingType2 Diabetes
- Interventions
- Other: Hybrid coolingOther: No cooling (control)Other: Recommended cooling
- Registration Number
- NCT05274009
- Lead Sponsor
- University of Ottawa
- Brief Summary
With the increasing incidence and severity of extreme heat events accompanying climate change, there is an urgent need for sustainable cooling strategies to protect heat-vulnerable older adults, who are at increased risk of adverse health events during heat stress. Health agencies including the World Health Organization, the United States Centers for Disease Control and Prevention, and Health Canada currently recommend visiting a cooling centre or other air-conditioned location for 1-3 hours per day during extreme heat events to mitigate hyperthermia and strain on the cardiovascular system and therefore the risk adverse health events. However, our recent trial shows that while brief air-conditioning exposure is effective for reducing body temperature and cardiovascular burden in healthy older adults, the physiological impacts of cooling abate quickly following return to the heat. The purpose of this project is therefore to assess whether shorter but more frequent air-conditioning exposure provides more effective cooling than current recommendations (a single 1-3-hour cooling bout) in older adults with or without common chronic health conditions associated with increased vulnerability to extreme heat. This will be accomplished by evaluating physiological strain in older adults with and without diabetes and/or hypertension exposed for 8 hours to conditions reflective of extreme heat events in temperate, continental climates (35°C, 60% relative humidity). Participants will complete 3 separate simulated heat event exposures: i) a control trial (no cooling throughout the 8-hour heat event); ii) a recommended cooling trial (3 hours of heat exposure followed by 2 hours cooling); and iii) a hybrid cooling trial (2 hours of heat exposure followed by 1 hour cooling, another 2 hours heat exposure followed by 1 hour cooling, and a final 2-hour heat exposure).
- Detailed Description
Not available
Recruitment & Eligibility
- Status
- NOT_YET_RECRUITING
- Sex
- All
- Target Recruitment
- 60
- Adult aged 60-85 years
- Male or female
- Body mass index < 35 kg/m2
- For participants with type 2 diabetes: at least one year lapsed since diagnosis and hemoglobin A1c 6.0-10.5%.
- For participants with hypertension: at least one year lapsed since diagnosis or average resting blood pressure >140 systolic or >90 diastolic
- Currently smoking or quit <5 years ago
- Moderate or serious medical conditions (other than Type 2 diabetes or high blood pressure), particularly those known to influence physiological responses to heat exposure (e.g., diagnosed heart disease, neurological disorders)
- Heat adapted due to repeated exposure to hot environments (use sauna, recent travel to hot climates, other)
- For participants with type 2 diabetes: "Brittle" diabetes: unpredictable hypo- & hyperglycemia. Severe cardiovascular autonomic or peripheral neuropathy (guidelines.diabetes.ca/cpg)
Study & Design
- Study Type
- INTERVENTIONAL
- Study Design
- CROSSOVER
- Arm && Interventions
Group Intervention Description Extreme heat event simulation + hybrid cooling Hybrid cooling Adults aged 60-85 years with or without type 2 diabetes and/or hypertension Extreme heat event simulation + no cooling (control) No cooling (control) Adults aged 60-85 years with or without type 2 diabetes and/or hypertension Extreme heat event simulation + recommended cooling Recommended cooling Adults aged 60-85 years with or without type 2 diabetes and/or hypertension
- Primary Outcome Measures
Name Time Method Core temperature (AUC) 8-hour heat exposure Rectal temperature will be measured continuously throughout each exposure and the area under the curve will be calculated.
Core temperature (peak) 8-hour heat exposure Peak rectal temperature measured during the 8-hour heat exposure.
- Secondary Outcome Measures
Name Time Method Heart rate temperature (peak) 8-hour heat exposure Peak rectal temperature measured during the 8-hour heat exposure.
Mean skin temperature Before and continuously throughout each 8 hour exposure Mean skin temperature calculated as a weighted average of skin temperatures at 8 body regions.
Body fluid loss Every hour during the 8-hour heat exposure Body fluid loss calculated as a change in body weight from pre-exposure values (corrected for food intake and deification).
Stand test: Systolic response to standing Prior to and following the 8-hour heat exposure Fall in systolic blood pressure after standing from a supine position.
Heart rate (AUC) 8-hour heat exposure Heart rate will be measured continuously throughout each exposure and the area under the curve will be calculated.
Arterial blood pressures Every hour during the 8-hour heat exposure Systolic and diastolic pressures measured in triplicate.
SDNN Every hour during the 8-hour heat exposure Standard deviation of normal-to-normal R-R intervals measured via 3-lead ECG.
RMSSD Every hour during the 8-hour heat exposure Root mean squared standard deviation of normal-to-normal R-R intervals measured via 3-lead ECG.
Rate pressure product Every hour during the 8-hour heat exposure Rate pressure product calculated as systolic blood pressure x heart rate.
Stand test: 30:15 ratio Prior to and following the 8-hour heat exposure 30:15 ratio calculated as the ratio of the RR interval measured after 30 heart beats following standing from a supine position to that measured after 15 heart beats.
Baroreflex sensitivity Prior to and following the 8-hour heat exposure Baroreflex sensitivity determined during cyclic stand-squat manoeuvres.
Change in plasma volume Prior to and following the 8-hour heat exposure Change in plasma volume calculated from venous blood samples (Dill and Costill technique)
Trial Locations
- Locations (1)
University of Ottawa
🇨🇦Ottawa, Ontario, Canada