NCT07501923

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

Randomized Controlled Crossover Trial on the Effects of Daytime, Nighttime, and Combined Heat Exposure on Human Health

• Status: Recruiting
• Phase: N/A
• Study type: Interventional
• Enrollment: 35 (estimated)
• Sponsor: Jian Cheng · Academic / Other
• Sex: All
• Age: 18 Years – 30 Years
• Healthy volunteers: Accepted

Summary

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.

Detailed 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.

Conditions

• Metabolism Changes
• Psychology Functional Behavior
• Cardiovascular System
• Respiratory System

Interventions

Type	Name	Description
OTHER	Daytime or Nighttime High-Temperature Exposure	Daytime Exposure Phase: The exposure group will be exposed to high temperature (32#) in a chamber for about 8 hours, resting during the whole periods Nighttime Exposure Phase: The exposure group will be exposed to high temperature (30#) in a chamber for about 8 hours, resting during the whole periods Day-Night Combined Exposure Phase: The exposure group will be exposed continuously to high temperatures during the day and night
OTHER	Daytime and nighttime neutral temperature exposure	Daytime Exposure Phase: The control group will be exposed to neutraltemperature (26#) in a chamber for about 8 hours, resting during the whole periods Nighttime Exposure Phase: The control group will be exposed to neutral temperature (26#) in a chamber for about 8 hours, resting during the whole periods Day-Night Combined Exposure Phase: The control group will be exposed continuously to neutraltemperatures during the day and night

Timeline

• Start date: 2025-06-01
• Primary completion: 2026-09-30
• Completion: 2026-12-31
• First posted: 2026-03-30
• Last updated: 2026-03-30

Locations

1 site across 1 country: China