Influence of Indoor Humidity on Physiological Strain in Older Adults During a Simulated Heat Wave

Официальное название

Is an Adjustment in the Recommended Indoor Temperature Upper Limit of 26°C Required During Higher Levels of Humidity?

Обзор

Laboratory-based studies show that exposure to high humidity can worsen the effects of heat stress in young and older adults by impeding sweat evaporation - the main mechanism by which the human body cools itself. At high levels of humidity, the efficiency of sweating decreases causing a greater rise core temperature and burden on the cardiovascular system. In this context, increasing temperatures and humidity with climate change thus pose a potential compound risk for human health. While humidity's role in heat-health outcomes could substantially alter projections of health burdens from climate change, the impact of humidity on physiological strain in vulnerable people in relation to the indoor environment has yet to be evaluated. In a recent study delineating the physiological effects of the proposed 26°C indoor upper limit (PMID: 38329752), relative humidity was set to 45% in all conditions based on indoor humidity standards by the American Society of Heating and Air-Conditioning Engineers. However, it is unknown whether a refinement of the recommended indoor temperature limit of 26°C is required in situations where humidity cannot be maintained at this level. On separate occasions, the investigators will assess the change in body temperature and cardiovascular strain in older adults (65-85 years) exposed for 10 hours at the recommended indoor temperature limit of 26°C and 45% relative humidity (equivalent humidex of 29 (considered comfortable)) (experimental condition A), to 26°C with a relative humidity of 15% (equivalent humidex of 23 (considered comfortable); humidex is used to measure the perceived temperature taking into account the humidity)) (experimental condition B), to 26°C with a relative humidity of 85% (equivalent humidex of 37 (considered somewhat uncomfortable)) (experimental condition C), and to 31°C and 45% relative humidity with an equivalent humidex of 37 (considered somewhat uncomfortable) that is similar to experimental condition C. With this experimental design, investigators will assess the effects of indoor humidity in driving human heat strain and identify whether refinements in the recommended 26°C indoor temperature limit may be required. Further, by evaluating changes in relation to ambient conditions with a similar humidex, the investigators can assess how individuals perceive and respond to both heat and humidity.

Вмешательства

• Другое Simulated indoor overheating
  Older adults are exposed to a 10-hour simulated exposure

Первичные конечные точки

• Core temperature (Peak) during daylong exposure to indoor overheating [Срок оценки: End of 10 hour daylong exposure]
• Core temperature (AUC) during daylong exposure to indoor overheating [Срок оценки: End of 10 hour daylong exposure]
• Heat rate (Peak) during daylong exposure to indoor overheating [Срок оценки: End of 10 hour daylong exposure]
• Heart rate (AUC) during daylong exposure to indoor overheating [Срок оценки: End of 10 hour daylong exposure]
• Cardiac response to standing from supine (30:15 Ratio) during daylong exposure to indoor overheating [Срок оценки: At the start (hour 0) and end of 10 hour daylong exposure]
• Systolic Response to Standing From Supine during daylong exposure to indoor overheating [Срок оценки: At the start (hour 0) and end of 10 hour daylong exposure]
• Heart rate variability: RMSSD during daylong exposure to indoor overheating [Срок оценки: At the start (hour 0) and end of 10 hour daylong exposure]
• Heart rate variability: SDNN during daylong exposure to indoor overheating [Срок оценки: At the start (hour 0) and end of 10 hour daylong exposure]
• Thermal comfort scale during daylong exposure to indoor overheating [Срок оценки: At the start (hour 0) and end of 10 hour daylong exposure]
• Thirst sensation scale during daylong exposure to indoor overheating [Срок оценки: At the start (hour 0) and end of 10 hour daylong exposure]

Вторичные конечные точки (8)

• Impulse control (cognitive function) during daylong exposure to indoor overheating [Срок оценки: At the start (hour 0) and end of 10 hour daylong exposure]
• Memory recall (cognitive function) during daylong exposure to indoor overheating [Срок оценки: At the start (hour 0) and end of 10 hour daylong exposure]
• CDC 4-Stage Balance Test (Postural stability) during daylong exposure to indoor overheating [Срок оценки: At the start (hour 0) and end of 10 hour daylong exposure]
• BTrackS Balance Assessment (Postural stability) during daylong exposure to indoor overheating [Срок оценки: At the start (hour 0) and end of 10 hour daylong exposure]
• Profiles of Mood States (POMS) during daylong exposure to indoor overheating [Срок оценки: At the start (hour 0) and end of 10 hour daylong exposure]
• Environmental Symptoms Questionnaire (ESQ) during daylong exposure to indoor overheating [Срок оценки: At the start (hour 0) and end of 10 hour daylong exposure]
• Sleepiness during daylong exposure to indoor overheating A [Срок оценки: At the start (hour 0) and end of 10 hour daylong exposure]
• Sleepiness during daylong exposure to indoor overheating B [Срок оценки: At the start (hour 0) and end of 10 hour daylong exposure]

Критерии участия

Критерии включения

• 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

Критерии исключения

• 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 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

Критерии приведены из реестра в оригинале (на английском). Окончательную оценку соответствия проводит исследовательский центр.

Здоровые добровольцы: Да

Дизайн исследования

Распределение

Рандомизированное

Модель

Перекрёстный дизайн

Маскирование

Простое слепое

Основная цель

Фундаментальное исследование

Центры проведения

Канада · 1 центр

• University of Ottawa — Ottawa

Идентификаторы

NCT: NCT06842953 · HEPRU-2025-02-A

Первоисточники (государственные реестры)

• ClinicalTrials.gov (NIH, США)

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