Protective Cooling Measures to Safeguard Elderly People From Dangerous Summer Heat

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

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).

Study Overview

• Status: Not yet recruiting
• Conditions: Hypertension; Hyperthermia; Aging; Type2 Diabetes; Heat Stress; Heat; Weather
• Intervention / Treatment: Other: No cooling (control); Other: Recommended cooling; Other: Hybrid cooling

• Study Type: Interventional
• Enrollment (Anticipated): 60
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Glen P Kenny, PhD; Phone Number: 4282 6135625800; Email: gkenny@uottawa.ca
• Study Contact Backup: Name: Robert D Meade, PhD; Phone Number: 6136986071; Email: rmead015@uottawa.ca

Study Locations

• Canada
  • Ontario
    • Ottawa, Ontario, Canada, K1N6N5
      • University of Ottawa
      • Contact: Glen P Kenny, PhD; Phone Number: 4282 6135625800; Email: gkenny@uottawa.ca
      • Contact: Robert D Meade, PhD; Phone Number: 6136986071; Email: rmead015@uottawa.ca

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 60 years to 85 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

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)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Double

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Extreme heat event simulation + no cooling (control); Adults aged 60-85 years with or without type 2 diabetes and/or hypertension	Other: No cooling (control); Participants are exposed to 35°C, 60% relative humidity for 8 hours.
Experimental: Extreme heat event simulation + recommended cooling; Adults aged 60-85 years with or without type 2 diabetes and/or hypertension	Other: 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.
Experimental: Extreme heat event simulation + hybrid cooling; Adults aged 60-85 years with or without type 2 diabetes and/or hypertension	Other: 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

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Core temperature (peak)	Peak rectal temperature measured during the 8-hour heat exposure.	8-hour heat exposure
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 Outcome Measures

Outcome Measure	Measure Description	Time Frame
Heart rate temperature (peak)	Peak rectal temperature measured during the 8-hour heat exposure.	8-hour heat exposure
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
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
Arterial blood pressures	Systolic and diastolic pressures measured in triplicate.	Every hour during the 8-hour heat exposure
SDNN	Standard deviation of normal-to-normal R-R intervals measured via 3-lead ECG.	Every hour during the 8-hour heat exposure
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
Rate pressure product	Rate pressure product calculated as systolic blood pressure x heart rate.	Every hour during the 8-hour heat exposure
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
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
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
Baroreflex sensitivity	Baroreflex sensitivity determined during cyclic stand-squat manoeuvres.	Prior to and following the 8-hour heat exposure
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

Collaborators and Investigators

• Sponsor: University of Ottawa
• Investigators: Principal Investigator: Glen P Kenny, PhD, University of Ottawa; Principal Investigator: Ronald J Sigal, MD, MPH, University of Calgary; Principal Investigator: Robert D Meade, PhD, University of Ottawa

Study record dates

Study Major Dates

• Study Start (Anticipated): May 1, 2023
• Primary Completion (Anticipated): May 1, 2024
• Study Completion (Anticipated): May 1, 2024

Study Registration Dates

• First Submitted: February 25, 2022
• First Submitted That Met QC Criteria: March 1, 2022
• First Posted (Actual): March 10, 2022

Study Record Updates

• Last Update Posted (Actual): October 21, 2022
• Last Update Submitted That Met QC Criteria: October 19, 2022
• Last Verified: October 1, 2022

More Information

Terms related to this study

• Keywords: Heat wave; Cooling center; Heat strain; Cardiovascular strain; Heat and health protection; Extreme heat events; Thermal comfort
• Additional Relevant MeSH Terms: Wounds and Injuries; Body Temperature Changes; Heat Stress Disorders; Hyperthermia
• Other Study ID Numbers: H-11-21-7566

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: Yes
• IPD Plan Description: Deidentified participant data will be available from Dr. Kenny upon reasonable request and signed access agreement.
• IPD Sharing Time Frame: After study completion
• IPD Sharing Access Criteria: Reasonable request and signed access agreement
• IPD Sharing Supporting Information Type: Study Protocol; Statistical Analysis Plan (SAP); Informed Consent Form (ICF); Analytic Code

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No