Mitigating Heat-induced Physiological Strain and Discomfort in Older Adults Via Lower Limb Immersion and Neck Cooling

Summary

The incidence and severity of hot weather and extreme heat events (heat waves) is increasing. As such, there is an urgent need to develop heat-alleviation strategies that can provide targeted protection for older adults who are at an elevated risk for heat-induced illnesses or death due to impaired body temperature and cardiovascular regulation. While air-conditioning provides the most effective protection from extreme heat, it is inaccessible for many individuals and cannot be used during power outages (e.g., heat-related rolling blackouts). Immersion of the lower limbs in cold water and/or the application of cold towels to the neck have been recommended as simple and sustainable alternatives to air-conditioning. However, empirical data to support the efficacy of these interventions for mitigating physiological strain and discomfort in older adults is lacking. To address this knowledge gap, this randomized crossover trial will evaluate the effect of lower limb immersion with and without application of cold towels to the neck on body core temperature, cardiovascular strain and autonomic function, dehydration, and thermal comfort in adults aged 65-85 years exposed to simulated heat wave conditions (38°C, 35% relative humidity) for 6 hours.

Conditions

• Hyperthermia
• Weather; Heat
• Heat Stress
• Heat Syncope
• Aging

Interventions

OTHER

No cooling (control)

Participants are exposed to 38°C, 35% relative humidity for 6 hours without cooling interventions (control condition). Drinking water is available ad libitum.

OTHER

Lower limb immersion

Participants are exposed to 38°C, 35% relative humidity for 6 hours. For the last 40 min of each hour, participants lower limbs are immersed in cool water (\~20°C) up to the level of mid calf. Drinking water is available ad libitum.

OTHER

Lower limb immersion + neck cooling

Participants are exposed to 38°C, 35% relative humidity for 6 hours. For the last 40 min of each hour, participants lower limbs are immersed in cool water (\~20°C) up to the level of mid calf. During limb immersion, a towel soaked in cool water (\~20°C) is placed around the participants neck. The towel is re-wet half way through the 40-min limb immersion. Drinking water is available ad libitum.

Sponsors & Collaborators

• University of Ottawa

  lead OTHER

Principal Investigators

• Glen P Kenny, PhD · University of Ottawa

• Robert D Meade, PhD · University of Ottawa

• Ronald J Sigal, MD, MPH · University of Calgary

Study Design

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

DOUBLE

Model

CROSSOVER

Eligibility

Min Age

65 Years

Max Age

85 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2022-09-28

Primary Completion

2023-05-04

Completion

2023-05-04

Countries

• Canada

Study Locations