The Effects of Daytime, Nighttime, and Combined Heat Exposure on Human Health

Jian Cheng

Status: Enrolling

Conditions: Cardiovascular System; Psychology Functional Behavior; Metabolism Changes; Respiratory System

Treatments: Other: Daytime and nighttime neutral temperature exposure; Other: Daytime or Nighttime High-Temperature Exposure

Study type: Interventional

Funder types: Other

Identifiers

NCT07501923

81250681

Details and patient eligibility

About

Assess the acute effects of high-temperature exposure (including both daytime and nighttime conditions) on multiple physiological and psychological indicators, including cardiovascular, respiratory, neuropsychiatric, and metabolic functions, along with their potential mechanisms.

Full description

This study will be conducted in Hefei, China, as a randomized controlled crossover human exposure trial involving approximately 50 healthy young adults. The primary objective is to systematically evaluate the acute effects of heat exposure-during both daytime and nighttime-on multiple physiological and psychological domains, including cardiovascular, respiratory, neurocognitive, and metabolic functions, and to explore the underlying biological mechanisms.

A randomized crossover design will be employed, comprising three exposure phases: nighttime heat exposure, daytime heat exposure, and combined day-night heat exposure. Each participant will undergo repeated exposures under different temperature conditions, with a washout period of at least three days between sessions to minimize carryover effects.

During the nighttime exposure phase, participants will be randomly assigned to one of two sequences. Group A will first be exposed to a nighttime heat condition at 30°C from 23:00 to 07:00 (8 hours, covering habitual sleep time), followed by exposure to a thermoneutral condition at 26°C after the washout period. Group B will follow the reverse sequence.

In the daytime exposure phase, participants will again be randomized in a crossover manner. Group A will first undergo exposure to a daytime heat condition at 32°C from 09:00 to 17:00 (8 hours, approximating a typical working day), followed by exposure to a 26°C thermoneutral condition after washout. Group B will receive the reverse sequence.

In the combined day-night exposure phase, a continuous heat exposure scenario will be simulated. Group A will first be exposed to both daytime heat (32°C, 09:00-17:00) and nighttime heat (30°C, 23:00-07:00), followed by a thermoneutral condition (26°C throughout the day and night) after washout. Group B will undergo the reverse order.

Throughout each exposure session, participants will remain in a resting state to minimize the confounding effects of physical activity. Health assessments will be conducted before exposure (within 1 hour prior), during exposure, and after exposure (within 2 hours post-exposure). These assessments will include, but are not limited to, ambulatory electrocardiogram (Holter) monitoring, blood pressure measurements, spirometry, cognitive function tests, psychological questionnaires, and collection of biological samples such as blood and urine. This comprehensive evaluation will enable characterization of the acute physiological responses to heat exposure and provide insights into potential mechanistic pathways.

Enrollment: 35 estimated patients

Sex: All

Ages: 18 to 30 years old

Volunteers: Accepts Healthy Volunteers

Inclusion criteria

• Age 18-30;
• In good health, with no history of cardiovascular disease, respiratory disease, diabetes, endocrine disorders, neurological or psychiatric conditions;
• No smoking or alcohol addiction, no history of substance abuse;
• No prior history of particular sensitivity to high-temperature environments.

Exclusion criteria

• Individuals who have experienced fever, colds, infectious diseases, or significant physical trauma within two weeks prior to the high-temperature test;
• Individuals currently using medications that may affect psychological, cognitive, cardiovascular, or respiratory functions;
• Pregnant women and lactating females;
• Participants shall not be scheduled to participate during menstruation;
• Individuals with a history of fainting or severe discomfort caused by high temperatures.

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Crossover Assignment

Masking: Single Blind

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35 participants in 2 patient groups

Intervention / Treatment

Other group

Description:

Daytime or Nighttime High-Temperature Group

Treatment:

Other: Daytime or Nighttime High-Temperature Exposure

Control

Other group

Description:

Daytime or Nighttime Neutral -Temperature Group

Treatment:

Other: Daytime and nighttime neutral temperature exposure