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

The Effect of Sleep Deprivation on Whole-body Heat Loss in Young and Older Men During Exercise in Hot, Dry Conditions

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.

Study Overview

• Status: Completed
• Conditions: Sleep Disturbance; Exercise; Aging; Thermoregulation; Heat Exchange
• Intervention / Treatment: Other: Normal sleep; Other: Sleep deprivation

• Study Type: Interventional
• Enrollment (Actual): 21
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Canada
  • Ontario
    • Ottawa, Ontario, Canada, K1N6N5
      • University of Ottawa

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Normal sleep; 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).	Other: Normal sleep; Participants will undertake ~8 hours of normal sleep prior to completing exercise
Experimental: Sleep deprivation; 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).	Other: Sleep deprivation; Participants will undertake a period of 24 hours of total sleep deprivation prior to completing exercise

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Evaporative heat loss	Evaporative heat loss as assessed using a direct air calorimeter	End of each exercise bout (average of last 5 minutes)
Whole-body heat loss	Net heat loss (dry plus/minus evaporative heat exchange) as assessed using a direct air calorimeter	End of each exercise bout (average of last 5 minutes)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Dry heat loss	Total dry heat loss as assessed using a direct air calorimeter	End of each exercise bout (average of last 5 minutes)
Body heat storage	Change in body heat storage (i.e., amount of heat stored in the body) calculated as the temporal summation of metabolic heat production and net heat loss	Each 30 minute exercise bout and sum of all three exercise bouts
Core temperature	Rectal temperature measured as an index of core temperature	End of each exercise bout (average of last 5 minutes)
Change in core temperature	Change in rectal temperature from baseline resting	End of each exercise bout (average of last 5 minutes)
Heart rate	Measured continuously using a heart rate monitor	End of each exercise bout (average of last 5 minutes)
Heart rate reserve	Percentage of the difference between the peak heart rate	End of each exercise bout (average of last 5 minutes)
Local sweat rate (forearm, scapula)	Sweat production assessed using ventilated capsule technique	End of each exercise bout (average of last 5 minutes)
Skin temperature	Skin temperature measured continuously at 4-sites (chest, upper arm, thigh, calf) with mean value calculated as weighted value of 4 sites - bicep, 30%; chest, 30%; thigh, 20%; and calf, 20%.	End of each exercise bout (average of last 5 minutes)
Skin temperature (change)	Change in skin temperature from baseline resting as assessed at 4-sites (chest, upper arm, thigh, calf) with mean value calculated as weighted value of 4 sites - bicep, 30%; chest, 30%; thigh, 20%; and calf, 20%.	End of each exercise bout (average of last 5 minutes)
Thermal comfort scale	Thermal comfort assessed via a self-report questionnaire upon verbal prompting (4-point scale; 1: comfortable to 4: very uncomfortable)	End of the 30 minute resting baseline period, end of each 30 minute exercise bout, end of each 15 minute rest period, and 1 hour after final exercise period.
Thermal sensation	Thermal sensation assessed via a self-report questionnaire upon verbal prompting (7-point scale; 0: neutral to 7: extremely hot)	End of the 30 minute resting baseline period, end of each 30 minute exercise bout, end of each 15 minute rest period, and 1 hour after final exercise period.
Thirst sensation	Thirst sensation assessed via a self-report questionnaire upon verbal prompting (9-point scale; 1: not thirsty at all to 9: very, very thirsty)	End of the 30 minute resting baseline period, end of each 30 minute exercise bout, end of each 15 minute rest period, and 1 hour after final exercise period.
Rating of perceived exertion	Perceived exertion assessed via a self-report questionnaire upon verbal prompting (6: no exertion at all to 20: maximal exertion)	End of the 30 minute resting baseline period, end of each 30 minute exercise bout, end of each 15 minute rest period, and 1 hour after final exercise period.
Stanford sleep scale	Symptoms of tiredness assess via a self-report questionnaire upon verbal prompting (How sleepy are you?) ranging from "feeling active, vital, alert, or wide awake" to "no longer fighting sleep, sleep onset soon, having dream-like thoughts"	End of the 30 minute resting baseline period, end of each 30 minute exercise bout, end of each 15 minute rest period, and 1 hour after final exercise period.
Variables of heart rate variability	Measures of variability computed from the time, frequency, time-frequency, scale-invariant, entropy, and other nonlinear domains (R-R interval data extracted from the electrocardiogram)	End of each exercise (average of last 5 minutes)

Collaborators and Investigators

• Sponsor: University of Ottawa

Study record dates

Study Major Dates

• Study Start (Actual): December 1, 2022
• Primary Completion (Actual): June 29, 2023
• Study Completion (Actual): June 29, 2023

Study Registration Dates

• First Submitted: March 30, 2023
• First Submitted That Met QC Criteria: April 18, 2023
• First Posted (Actual): May 1, 2023

Study Record Updates

• Last Update Posted (Actual): July 15, 2024
• Last Update Submitted That Met QC Criteria: July 12, 2024
• Last Verified: July 1, 2024

More Information

Terms related to this study

• Keywords: Sleep; Physical activity; Aging; Heat stress; Heat dissipation
• Additional Relevant MeSH Terms: Mental Disorders; Nervous System Diseases; Dyssomnias; Sleep Wake Disorders; Neurologic Manifestations; Sleep Deprivation
• Other Study ID Numbers: HEPRU-2023-01

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Deidentified participant data will be made available with approved analysis plan and signed access agreement
• IPD Sharing Time Frame: Following publication of the main study (report(s)
• IPD Sharing Access Criteria: Approved analysis plan and signed access agreement
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ANALYTIC_CODE

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No