Acute Sleep Deprivation on Whole-body Heat Exchange During Exercise-heat Stress in Young and Older Men

University of Ottawa

Status: Completed

Conditions: Aging; Thermoregulation; Heat Exchange; Sleep Disturbance; Exercise

Treatments: Other: Sleep deprivation; Other: Normal sleep

Study type: Interventional

Funder types: Other

Identifiers

NCT05838014

HEPRU-2023-01

Details and patient eligibility

About

Sleep deprivation has long been thought to modulate thermoregulatory function. Seminal work on sleep deprivation and thermoregulation has demonstrated that sleep-deprived individuals experience greater elevations in core temperature during exercise-heat stress due to reductions in the activation of local heat loss responses of cutaneous vasodilation and sweating. However, it remains unclear 1) if reductions in local heat loss responses would compromise whole-body heat loss (evaporative + dry heat exchange) and 2) if differences exist, are they dependent on the heat load generated by exercise (increases in metabolic rate augments the rate that heat must be dissipated by the body). Further, much of the understanding of the effects of sleep deprivation on thermoregulation has been limited to assessments in young adults. Studies show that aging is associated with reduction in cutaneous vasodilation and sweating that compromise whole-body heat loss exacerbating body heat storage during moderate- and especially more vigorous-intensity exercise in the heat. However, it remains unclear if sleep deprivation may worsen this response in older adults.

The purpose of this study is therefore to evaluate the effects of sleep-deprivation on whole-body total heat loss during light, moderate, and vigorous exercise-heat stress and to assess if aging may mediate this response. To achieve this objective, direct calorimetry will be employed to measure whole-body total heat loss in young (18-30 years) and older (50-65 years) men during exercise at increasing, fixed rates of metabolic heat production of 150 (light), 200 (moderate), and 250 W/m2 (vigorous) in dry heat (40°C, ~15% relative humidity) with and without 24 hours of sleep deprivation.

Enrollment: 21 patients

Sex: Male

Ages: 18 to 65 years old

Volunteers: Accepts Healthy Volunteers

Inclusion criteria

• healthy young (18-30 years) and older males (50-65 years)
• non-smoking
• English or French speaking
• ability to provide informed consent

Exclusion criteria

• presence of chronic diseases (e.g., hypertension, diabetes)
• acute illness (e.g., flu, COVID-19)
• physical restriction limiting physical activity (e.g., severe arthritis, etc.)
• use of medication judged by the patient or investigators to make participation in this study inadvisable
• engaged in regular endurance training

Trial design

Primary purpose: Basic Science

Allocation: Randomized

Interventional model: Crossover Assignment

Masking: None (Open label)

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21 participants in 2 patient groups

Normal sleep

Active Comparator group

Description:

Participants will complete three 30-minute bouts of semi-recumbent cycling at incrementally increasing fixed metabolic heat loads (150, 200 and 250 W/m2) in a hot, dry condition (40°C, 15% relative humidity). Each exercise bout will be separated by a 15 minute period of rest, with the final recovery 1 hour in duration. Exercise will commence between the hours of 7 AM and 9 AM following a period of normal sleep (\~8 hours) (Control condition).

Treatment:

Other: Normal sleep

Sleep deprivation

Experimental group

Description:

Participants will complete three 30-minute bouts of semi-recumbent cycling at incrementally increasing fixed metabolic heat loads (150, 200 and 250 W/m2) in a hot, dry condition (40°C, 15% relative humidity). Each exercise bout will be separated by a 15 minute period of rest, with the final recovery 1 hour in duration. Exercise will commence between the hours of 7 AM and 9 AM following a period of 24 hour of sleep deprivation (Sleep deprivation condition).

Treatment:

Other: Sleep deprivation