Understanding and Managing the Limits of Physiological Tolerance in Heat Vulnerable Canadians During Rest and Physical Exercise
试验速览
- 阶段
- 不适用
- 状态
- 已完成
- 入组人数
- 60
- 试验地点
- 2
- 主要终点
- Body heat storage
研究概览
简要总结
Climate change not only affects the planet's natural resources, but also severely impacts human health. An individual's ability to adequately cope with short- or long-term increases in ambient temperature is critical for maintaining health and wellbeing. Prolonged increases in temperature (heatwaves) pose a serious health risk for older adults, who have a reduced capacity to efficiently regulate body temperature. However, information regarding the impact of age on body temperature regulation during prolonged exposure to extreme heat is lacking, as is research on the effectiveness of interventions aimed at reducing heat strain in such situations. This project will address these important knowledge gaps by exposing healthy young and older adults to a prolonged (9 hour) heat exposure, with conditions representative of heatwaves in temperate continental climates. An additional cohort of older adults will complete the same heatwave simulation but will be briefly (2 hours) exposed to cooler conditions (22-23°C) mid-way through the session (akin to visiting a cooling centre or cooled location). The investigators will evaluate age-related differences in the capacity to dissipate heat via direct air calorimetry (a unique device that permits the precise measurement of the heat dissipated by the human body) and their effect on the regulation of body temperature. The investigators anticipate that older adults will exhibit progressive increases in the heat stored in the body throughout the simulated heatwave, resulting in progressive increases in body core temperature. Further, older adults exposed to brief-mid day cooling will rapidly gain heat upon re-exposure to high ambient temperatures. As a result, by the end of exposure body temperatures will be similar to the group not removed from the heat.
详细描述
OBJECTIVES Intervention 1: Evaluate the effect of age on whole-body heat storage, body core temperature, and the development of cardiovascular strain and acute inflammation during day-long (9 hours) exposure to simulated heatwave conditions.
Intervention 2: Determine whether short-duration exposure (2 hours) to an air-conditioned environment following extreme heat exposure results in lasting reductions in physiological strain in older adults upon return to the heat.
Hypotheses Intervention 1: Older adults will experience greater heat storage throughout the 9-hour simulated heatwave compared to the younger participants. Consequently, body core temperature will be greater in the older adults and between-group differences will be exacerbated as exposure progresses. We will also explore the secondary hypothesis that differences in body temperature will be paralleled by greater alterations in cardiovascular variables and acute circulatory and intracellular inflammation in the older adults.
Intervention 2: Body heat storage will be exacerbated in the older adults exposed to the cooling centre intervention upon return to the heat (hours 5-6) compared to the older adults from Intervention 1 who remained in the heat. Consequently, body core temperature will be comparable (statistically equivalent) between groups by the end of exposure.
Methods Participants A total of 20 young (age: 18-31 years) and 40 older (age: 64-80 years) adults will be recruited for the proposed project, with an approximately even distribution of men and women in each intervention arm. Young (n = 20) and older (n = 20) adults will complete Intervention 1 and a separate cohort of older adults (n = 20) will complete Intervention 2. Participants will be homogenous for anthropomorphic characteristics as well as habitual physical activity levels as verified via standardized questionnaires.
研究设计
- 研究类型
- Interventional
- 分配方式
- Non Randomized
- 干预模型
- Parallel
- 主要目的
- Basic Science
- 盲法
- None
入排标准
- 年龄范围
- 18 Years 至 80 Years（Adult, Older Adult）
- 性别
- All
- 接受健康志愿者
- 是
入选标准
- •male or female (non-pregnant) adults 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 and or c) obesity as defined by the World Health Organization (Body Mass Index [BMI] greater than or equal to 30).
- •non-smoking.
排除标准
- •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 in your physical health screening form (adults <65 years of age and older; adults <60 years of age and older with diabetes and or hypertension) or during exercise stress testing as assessed by 12-lead (all adults ≥65 years of age and older).
结局指标
主要结局
Body heat storage
时间窗: Final 3 hours (hours 7-9) of simulated heatwave
Cumulative amount of heat stored within the body
Rectal temperature
时间窗: Hour 9 of simulated heatwave
Index of core body temperature
次要结局
- Change in plasma volume(Hour 9 of simulated heatwave)
- Circulating inflammatory and stress markers(Hour 9 of simulated heatwave)
- Systolic blood pressure(Hour 9 of simulated heatwave)
- Cardiac baroreflex sensitivity(Hour 9 of simulated heatwave)
- Heart rate(Hour 9 of simulated heatwave)
- Rate pressure product(Hour 9 of simulated heatwave)
- Heart rate variability: SDNN(Hour 9 of simulated heatwave)
- Diastolic blood pressure(Hour 9 of simulated heatwave)
- Mean arterial pressure(Hour 9 of simulated heatwave)
- Heart rate variability: RMSSD(Hour 9 of simulated heatwave)
- Intracellular inflammatory and stress markers(Hour 9 of simulated heatwave)
研究者
Glen P. Kenny
Full Professor, University Research Chair
University of Ottawa