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

NCT05601713 | Completed

• 1 other identifier: H-11-20-6234
• Study Type: interventional
• Target: 18
• Locations: 1 country
• Sites: 1

Brief 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

Keywords

Heat wave; Cooling intervention; Heat strain; Cardiovascular strain; Heat and health protection; Extreme heat events

Outcome Measures

Primary Outcomes (1)

• Core temperature

  Rectal temperature measured as an index of core temperature (15 minute average)

  End of heat exposure (hour 6)

Secondary Outcomes (14)

• Heart rate

  End of heat exposure (hour 6)

• Systolic blood pressure

  End of heat exposure (hour 6)

• Diastolic blood pressure

  End of heat exposure (hour 6)

• Rate pressure product

  End of heat exposure (hour 6)

• Heart rate variability: SDNN

  End of heat exposure (hour 6)

Study Arms (3)

No cooling intervention (control)

ACTIVE COMPARATOR

Adults aged 65-85 years with or without type 2 diabetes and/or hypertension.

Other: No cooling (control)

Lower limb immersion

EXPERIMENTAL

Adults aged 65-85 years with or without type 2 diabetes and/or hypertension.

Other: Lower limb immersion

Lower limb immersion + neck cooling

EXPERIMENTAL

Adults aged 65-85 years with or without type 2 diabetes and/or hypertension.

Other: Lower limb immersion + neck cooling

Interventions

No cooling (control) OTHER

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

No cooling intervention (control)

Lower limb immersion OTHER

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.

Lower limb immersion

Lower limb immersion + neck cooling OTHER

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.

Lower limb immersion + neck cooling

Eligibility Criteria

• Age: 65 Years - 85 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Older Adult (65+)

You may qualify if:

• Male or female adults.
• Aged 65-85 years.
• Non-smoking.
• English or French speaking.
• Ability to provide informed consent.

You may not qualify if:

• Physical restriction (e.g., due to disease: intermittent claudication, renal impairment, active proliferative retinopathy, unstable cardiac or pulmonary disease, disabling stroke, severe arthritis, etc.).
• Use of or changes in medication judged by the patient or investigators to make participation in this study inadvisable (e.g., medications increasing risk of heat-related illness; beta blockers, anticholinergics, etc.)
• Cardiac abnormalities identified via 12-lead ECG during an incremental exercise test to volitional fatigue (performed for all participants).
• Peak aerobic capacity (VO2peak), as measured during an incremental exercise test to volitional fatigue, exceeding the 50th percentile of age- and sex-specific normative values published by the American College of Sports Medicine (ACSM).

Sponsors & Collaborators

• University of Ottawa: lead

Study Sites (1)

University of Ottawa

Ottawa, Ontario, K1N6N5, Canada

Location

MeSH Terms

Conditions

Hyperthermia; Heat Stress Disorders

Condition Hierarchy (Ancestors)

Body Temperature Changes; Signs and Symptoms; Pathological Conditions, Signs and Symptoms; Wounds and Injuries

Study Officials

• Glen P Kenny, PhD

  University of Ottawa

  PRINCIPAL INVESTIGATOR

• Robert D Meade, PhD

  University of Ottawa

  PRINCIPAL INVESTIGATOR

• Ronald J Sigal, MD, MPH

  University of Calgary

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, OUTCOMES ASSESSOR
• Masking Details: Participants will be informed of the study interventions before providing informed consent but will be masked to the specific trial until exposure (i.e., participants will not know the cooling intervention before the trial or during baseline measurements). Data will be blinded prior to analysis.
• Purpose: BASIC SCIENCE
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Full Professor, University Research Chair

Model Details: Participant will complete 3 simulated extreme heat event exposures in random order: i) no cooling intervention (control); ii) lower limb water immersion; and iii) lower limb water immersion with application of cool wet towel to the neck.

Study Record Dates

• First Submitted: October 19, 2022
• First Posted: November 1, 2022
• Study Start: September 28, 2022
• Primary Completion: May 4, 2023
• Study Completion: May 4, 2023
• Last Updated: May 10, 2023

Record last verified: 2023-05

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP, ANALYTIC CODE
• Time Frame: Following publication of the main study report(s)
• Access Criteria: Approved analysis plan and signed access agreement

Locations

CA (1)