Protective Cooling Measures to Safeguard Elderly People From Dangerous Summer Heat

Hypertension Clinical Trial

Official title:

Evaluating the Efficacy of Cooling Centres for Limiting Heat Strain in Elderly Adults During Extreme Heat Events

Clinical Trial Details — Status: Not yet recruiting

Administrative data

• NCT number: NCT05274009
• Other study ID #: H-11-21-7566
• Status: Not yet recruiting
• Phase: N/A
• Start date: May 2023
• Est. completion date: May 2024

Study information

• Verified date: October 2022
• Source: University of Ottawa
• Contact: Glen P Kenny, PhD
• Phone: 6135625800
• Email: gkenny[@]uottawa.ca
• Is FDA regulated: No
• Study type: Interventional

Clinical Trial 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).

Recruitment information / eligibility

• Status: Not yet recruiting
• Enrollment: 60
• Est. completion date: May 2024
• Est. primary completion date: May 2024
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: All
• Age group: 60 Years to 85 Years

Eligibility

Inclusion Criteria:

• 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

Exclusion Criteria:

• 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)

Related Conditions & MeSH terms

• Aging
• Heat Stress
• Hypertension
• Hyperthermia
• Type2 Diabetes

Intervention

Other:
• No cooling (control)
Participants are exposed to 35°C, 60% relative humidity for 8 hours.
• Recommended cooling
Participants are exposed to 35°C, 60% relative humidity for 3 hours, are then moved to an air-conditioned room for 2 hours (~23°C, ~50% relative humidity), and then return to the heat for a final 3 hours.
• Hybrid cooling
Participants are exposed to 35°C, 60% relative humidity for 2 hours, are moved to an air-conditioned room for 1 hour (~23°C, ~50% relative humidity), return to the heat for 2 hours, move back to the air-conditioned room for 1 hour, and then return to the heat for a final 2 hours

Locations

Country	Name	City	State
Canada	University of Ottawa	Ottawa	Ontario

Sponsors (1)

Lead Sponsor	Collaborator
University of Ottawa

Country where clinical trial is conducted

Canada, 

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Core temperature (peak)	Peak rectal temperature measured during the 8-hour heat exposure.	8-hour heat exposure
Primary	Core temperature (AUC)	Rectal temperature will be measured continuously throughout each exposure and the area under the curve will be calculated.	8-hour heat exposure
Secondary	Heart rate temperature (peak)	Peak rectal temperature measured during the 8-hour heat exposure.	8-hour heat exposure
Secondary	Heart rate (AUC)	Heart rate will be measured continuously throughout each exposure and the area under the curve will be calculated.	8-hour heat exposure
Secondary	Mean skin temperature	Mean skin temperature calculated as a weighted average of skin temperatures at 8 body regions.	Before and continuously throughout each 8 hour exposure
Secondary	Arterial blood pressures	Systolic and diastolic pressures measured in triplicate.	Every hour during the 8-hour heat exposure
Secondary	SDNN	Standard deviation of normal-to-normal R-R intervals measured via 3-lead ECG.	Every hour during the 8-hour heat exposure
Secondary	RMSSD	Root mean squared standard deviation of normal-to-normal R-R intervals measured via 3-lead ECG.	Every hour during the 8-hour heat exposure
Secondary	Rate pressure product	Rate pressure product calculated as systolic blood pressure x heart rate.	Every hour during the 8-hour heat exposure
Secondary	Body fluid loss	Body fluid loss calculated as a change in body weight from pre-exposure values (corrected for food intake and deification).	Every hour during the 8-hour heat exposure
Secondary	Stand test: 30:15 ratio	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.	Prior to and following the 8-hour heat exposure
Secondary	Stand test: Systolic response to standing	Fall in systolic blood pressure after standing from a supine position.	Prior to and following the 8-hour heat exposure
Secondary	Baroreflex sensitivity	Baroreflex sensitivity determined during cyclic stand-squat manoeuvres.	Prior to and following the 8-hour heat exposure
Secondary	Change in plasma volume	Change in plasma volume calculated from venous blood samples (Dill and Costill technique)	Prior to and following the 8-hour heat exposure