Clinical trial NCT06670365: Enhancing Heat Resiliency in Older Adults During Indoor Overheating Via Heat Acclimation by Warm Water Immersion
Official title: Evaluating the Efficacy of Heat Acclimation by Warm Water Immersion for Mitigating Hyperthermia and Cardiovascular Demand in Older Adults During Indoor Overheating.
Study type: INTERVENTIONAL
Overall status: RECRUITING
Phase: NA
Conditions: Hyperthermia
Thermoregulation
Aging
Heat Acclimation and Thermotolerance
Keywords: thermoregulation
heat illness
heat acclimation
extreme heat events
women
indoor overheating
water immersion
Lead sponsor: University of Ottawa
Sponsor class: OTHER
First posted: 2024-11-01
Enrollment: 12
Sex: FEMALE
Minimum age (years): 65
Maximum age (years): 85
Standard ages: OLDER_ADULT
Accepts healthy volunteers: yes
Allocation: NA
Intervention model: SINGLE_GROUP
Primary purpose: BASIC_SCIENCE

Brief summary: As overheating in buildings is expected to increase as global warming continues, proactive measures to increase heat resiliency in heat-vulnerable older people are needed, especially for those without access to home cooling or reliable sources of electricity. While short-term heat acclimation through exercise in the heat has been shown to increase heat dissipation and decrease both the physical and mental stress imposed on individuals exposed to heat, such protocols are not tenable for older, sedentary adults. A recent report showed that seven consecutive days of warm-water immersion improved whole-body heat loss and reduced physiological strain as assessed during an exercise-heat stress in habitually active older men This represents a critical finding as an increase heat-loss capacity would serve as an important safeguard for older adults exposed to indoor overheating due to lack of air-conditioning. While this preliminary data highlights passive hot water immersion as a promising strategy for increasing heat-resilience in vulnerable adults, work is needed to confirm its efficacy in more "real-world" environments. Thus, this study aims to assess the effectiveness of a 7-day passive heating (warm-water immersion with core temperature clamped at \~38.5°C for the final 60 minutes) protocol in mitigating increases in thermal and cardiovascular strain in older females exposed to daylong (10-hours) indoor overheating (36°C, 45% relative humidity) prior to and following the passive heating intervention. Relative to males, females have a reduced heat loss capacity (\~5%), which is driven by differences in the activation of heat loss responses (i.e., skin blood flow and sweating). Although there have been mixed findings with regards to the influence of sex as a mediating factor for heat-related mortality, some studies suggest that females are at a higher risk of heat-related mortality and morbidity compared to males, especially amongst older individuals (≥65 years). Notably, a greater proportion of older females died compared to their male counterparts during the 2021 Western Heat Dome. While the underlying causes for these differences remain unclear, greater cardiovascular strain may place females at higher mortality risk during extreme heat.


Eligibility criteria: Inclusion Criteria:

* Non-smoking.
* English or French speaking.
* Ability to provide informed consent.
* With or without a) chronic hypertension (elevated resting blood pressure; as defined by Heart and Stroke Canada and Hypertension Canada), b) type 2 diabetes as defined by Diabetes Canada, with at least 5 years having elapsed since time of diagnosis

Exclusion Criteria:

* Episode(s) of severe hypoglycemia (requiring the assistance of another person) within the previous year, or inability to sense hypoglycemia (hypoglycemia unawareness).
* Serious complications related to your diabetes (gastroparesis, renal disease, uncontrolled hypertension, severe autonomic neuropathy).
* Uncontrolled hypertension - BP \>150 mmHg systolic or \>95 mmHg diastolic in a sitting position.
* Restrictions in physical activity due to disease (e.g. 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.
* Cardiac abnormalities identified during screening

Primary outcomes:
measure: Core temperature (Peak) during daylong heat exposure
timeFrame: End of 10 hour daylong heat exposure
measure: Core temperature (AUC) during daylong heat exposure
timeFrame: End of 10 hour daylong heat exposure
measure: Heat rate (Peak) during daylong heat exposure
timeFrame: End of 10 hour daylong heat exposure
measure: Heat rate (AUC) during daylong heat exposure
timeFrame: End of 10 hour daylong heat exposure
measure: Cardiac response to standing from supine (30:15 Ratio) during daylong heat exposure
timeFrame: At the start (hour 0) and end of daylong heat exposure (hour 10)
measure: Systolic Response to Standing From Supine during daylong heat exposure
timeFrame: At the start (hour 0) and end of the daylong heat exposure (hour 10)
measure: Heart rate variability: RMSSD during daylong heat exposure
timeFrame: At the start (hour 0) and end of the daylong heat exposure (hour 10)
measure: Heart rate variability: SDNN during daylong heat exposure
timeFrame: At the start (hour 0) and end of daylong heat exposure (hour 10)
measure: Thermal comfort scale during daylong heat exposure
timeFrame: End of 10 hour daylong heat exposure
measure: Thirst sensation scale during daylong heat exposure
timeFrame: End of 10 hour daylong heat exposure
measure: Thermal sensation scale during daylong heat exposure
timeFrame: End of 10 hour daylong heat exposure
measure: Arousal scale during daylong heat exposure
timeFrame: End of 10 hour daylong heat exposure
measure: Fluid loss during daylong heat exposure
timeFrame: End of 10 hour daylong heat exposure
measure: Fluid consumption during daylong heat exposure
timeFrame: End of 10 hour daylong heat exposure
measure: Changes in plasma volume during daylong heat exposure
timeFrame: End of 10 hour daylong heat exposure
measure: Systolic blood pressure during daylong heat exposure
timeFrame: End of 10 hour daylong heat exposure
measure: Diastolic blood pressure during daylong heat exposure
timeFrame: End of 10 hour daylong heat exposure
measure: Systolic Response to Standing From Supine during daylong heat exposure
timeFrame: End of 10 hour daylong heat exposure
measure: Rate pressure product during daylong heat exposure
timeFrame: At the start (hour 0) and end of the daylong heat exposure (hour 10)
measure: Orthostatic intolerance symptoms assessment during daylong heat exposure
timeFrame: End of 10 hour daylong heat exposure
measure: Reaction time (cognitive function) during daylong heat exposure
timeFrame: At the start (hour 0) and end of the daylong heat exposure (hour 10)
measure: Impulse control (cognitive function) during daylong heat exposure
timeFrame: At the start (hour 0) and end of the daylong heat exposure (hour 10)
measure: Memory recall (cognitive function) during daylong heat exposure
timeFrame: At the start (hour 0) and end of the daylong heat exposure (hour 10)
measure: CDC 4-Stage Balance Test (Postural stability) during daylong heat exposure
timeFrame: At the start (hour 0) and end of the daylong heat exposure (hour 10)
measure: BTrackS Balance Assessment (Postural stability) during daylong heat exposure
timeFrame: At the start (hour 0) and end of the daylong heat exposure (hour 10)
Secondary outcomes:
measure: Muscle oxygen during battery of cardiovascular, cognition and postural stability tests during daylong heat exposure
timeFrame: At the start (hour 0) and end of the daylong heat exposure (hour 10)
measure: Profiles of Mood States (POMS) during daylong heat exposure
timeFrame: At the start (hour 0) and end of the daylong heat exposure (hour 10)
measure: Environmental Symptoms Questionnaire (ESQ)
timeFrame: At the start (hour 0) and end of the daylong heat exposure (hour 10)
measure: Sleepiness during daylong heat exposure A
timeFrame: End of 10 hour daylong heat exposure
measure: Sleepiness during daylong heat exposure B
timeFrame: End of 10 hour daylong heat exposure
Other outcomes:
Locations:
city: Ottawa
country: Canada
facility: University of Ottawa
state: Ontario
Study officials:
affiliation: University of Ottawa
name: Glen P Kenny, PhD
role: PRINCIPAL_INVESTIGATOR
References: