Clinical trial NCT06633302: Physiological Strain in Older Adults During a Simulated Heat Wave
Official title: Evaluating the Efficacy of a 26°C Indoor Temperature for Limiting Thermal and Cardiovascular Strain in Older Adults During a Simulated Multi-day Heat Event
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Heat Stress
Physiological Stress
Keywords: Heat wave
Indoor overheating
Indoor temperatures
Thermoregulation
Heat strain
Elderly
Heat vulnerability
Cardiovascular strain
Sleep
Hyperthermia
Fatigue
Lead sponsor: University of Ottawa
Sponsor class: OTHER
First posted: 2024-10-09
Enrollment: 18
Sex: ALL
Minimum age (years): 65
Maximum age (years): 85
Standard ages: OLDER_ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: CROSSOVER
Primary purpose: BASIC_SCIENCE

Brief summary: A recent report showed that maintaining indoor temperature at or below 26°C safeguards older, heat vulnerable adults against potentially dangerous increases in thermal and cardiovascular strain during an extreme heat event (PMID: 38329752). However, this proposed limit does not consider the potential cumulative effect of successive days of heat exposure, which could lead to a progressive deterioration in thermoregulatory and cardiovascular function and necessitate adjustments to upper indoor temperature limits. Further, thermal comfort and quality of sleep may be negatively impacted when bedroom temperatures exceed 24°C (PMID: 3090680). On this basis, some health agencies have recommended that bedroom temperatures at night should not exceed 26°C unless ceiling fans are available (PMID: 3090680). Currently, however, it is unknown whether indoor overheating impairs sleep quality and physiological strain on a subsequent day in older adults and, if so, whether maintaining indoor temperature at 26°C is sufficient to prevent these adverse health impacts.

With rising global temperatures and more extreme heat events, energy management strategies to limit the strain on the power grid during the daytime are now increasingly commonplace. Thus, understanding the benefits of maintaining indoor temperature at the recommend upper limits of 26°C during the nighttime only on surrogate physiological indicators of health is an important step in understanding how to optimize protection for heat-vulnerable older adults when power outages occur.

The investigators will assess the efficacy of proposed indoor temperature limits (i.e., 26°C) in mitigating increases in core temperature and cardiovascular strain over three consecutive days (3 days, 2 nights) in older adults (60-85 years) with (indoor temperatures maintained at the recommend 26°C at all times throughout the three days) and without (daytime temperature fixed at 34°C (temperature experienced in homes without air-conditioning during an extreme heat event) with nighttime temperature at 26°C) access to daytime cooling. By quantifying the effect of daylong indoor overheating on surrogate physiological outcomes linked with heat-related mortality and morbidity in older adults, the investigators can determine if refinements in the recommended upper temperature threshold is required, including best practices when power outages may occur during an extreme heat event.


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 daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Core temperature (AUC) during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Core temperature end of daytime exposure
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Heat rate peak during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Heat rate AUC during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Cardiac response to standing from supine (30:15 Ratio) during daytime
timeFrame: At the start (hour 0) and end of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Reaction time during daytime (cognitive function)
timeFrame: At the start (hour 0) and end of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Impulse control during daytime (cognitive function)
timeFrame: At the start (hour 0) and end of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Memory recall during daytime (cognitive function)
timeFrame: At the start (hour 0) and end of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Executive function during daytime (cognitive function)
timeFrame: At the start (hour 0) and end of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: CDC 4-Stage Balance Test during daytime (Postural stability)
timeFrame: At the start (hour 0) and end of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: BTrackS Balance Assessment during daytime (Postural stability)
timeFrame: At the start (hour 0) and end of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Systolic Response to Standing From Supine during daytime
timeFrame: At the start (hour 0) and end of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Systolic blood pressure during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Diastolic blood pressure during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Rate pressure product during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Heart rate variability: SDNN during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Heart rate variability: RMSSD during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Fluid consumption during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Fluid loss during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Change in plasma volume during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Thermal comfort scale during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Thermal sensation scale during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Thirst sensation scale during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Arousal scale during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Orthostatic intolerance symptoms assessment during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Core temperature (Peak) during nighttime
timeFrame: End of nighttime exposure (hour 24 for Day 1 and Day 2 of the three day exposure; no nighttime exposure for Day 3) (daytime defined as period between 19:00 to 9:00)
measure: Core temperature (AUC) during nighttime
timeFrame: End of nighttime exposure (hour 24 for Day 1 and Day 2 of the three day exposure; no nighttime exposure for Day 3) (daytime defined as period between 19:00 to 9:00)
measure: Core temperature end of nighttime
timeFrame: End of nighttime exposure (hour 24 for Day 1 and Day 2 of the three day exposure; no nighttime exposure for Day 3) (daytime defined as period between 19:00 to 9:00)
measure: Heat rate peak during nighttime
timeFrame: End of nighttime exposure (hour 24 for Day 1 and Day 2 of the three day exposure; no nighttime exposure for Day 3) (daytime defined as period between 19:00 to 9:00)
measure: Heat rate AUC during nighttime
timeFrame: End of nighttime exposure (hour 24 for Day 1 and Day 2 of the three day exposure; no nighttime exposure for Day 3) (daytime defined as period between 19:00 to 9:00)
measure: Heart rate variability: SDNN during nighttime
timeFrame: End of nighttime exposure (hour 24 for Day 1 and Day 2 of the three day exposure; no nighttime exposure for Day 3) (daytime defined as period between 19:00 to 9:00)
measure: Heart rate variability: RMSSD during nighttime
timeFrame: End of nighttime exposure (hour 24 for Day 1 and Day 2 of the three day exposure; no nighttime exposure for Day 3) (daytime defined as period between 19:00 to 9:00)
Secondary outcomes:
measure: Muscle oxygen during battery of cardiovascular, postural and cognitive tests during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Profiles of Mood States (POMS) during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Environmental Symptoms Questionnaire (ESQ)
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Sleep quality and quantify assessment
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
measure: Sleepiness during daytime
timeFrame: End of daytime exposure (hour 10 for Day 1, 2 and 3 of the three day exposure) (daytime defined as period between 9:00 to 19:00)
Other outcomes:
Locations:
city: Ottawa
country: Canada
facility: University of Ottawa
state: Ontario
Study officials:
References: