Protective Cooling Measures to Safeguard Elderly People From Dangerous Summer Heat

University of Ottawa60 enrolled

Overview

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 Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

DOUBLE

Enrollment

Interventions

No cooling (control)OTHER

Participants are exposed to 35°C, 60% relative humidity for 8 hours.

Recommended coolingOTHER

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 coolingOTHER

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

Eligibility

Sex: ALLMin age: 60 YearsMax age: 85 YearsHealthy volunteers:

Medical Language ↔ Plain English

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)

Outcomes

Primary Outcomes

Core temperature (peak)

Peak rectal temperature measured during the 8-hour heat exposure.

Time frame: 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.

Time frame: 8-hour heat exposure

Secondary Outcomes

Heart rate temperature (peak)

Peak rectal temperature measured during the 8-hour heat exposure.

Time frame: 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.

Time frame: 8-hour heat exposure

Mean skin temperature

Mean skin temperature calculated as a weighted average of skin temperatures at 8 body regions.

Time frame: Before and continuously throughout each 8 hour exposure

Arterial blood pressures

Systolic and diastolic pressures measured in triplicate.