Agnirva Space Premier League - Expedition #32183: How Light and Sleep Cycles Affect Astronauts Aboard ISS-12

The human body is deeply tied to a biological rhythm known as the circadian cycle. This natural cycle influences when we feel sleepy or awake, and it is heavily affected by light exposure. On Earth, this system works smoothly due to the predictable cycle of day and night. But what happens when humans are in space, orbiting the Earth every 90 minutes and experiencing 16 sunrises and sunsets a day?

The Sleep-Wake Actigraphy and Light Exposure on ISS-12 experiment, spearheaded by Dr. Laura Barger of Harvard Medical School and conducted during Expeditions 43/44 and 45/46, tackled this complex issue. The goal: to understand how light conditions aboard the International Space Station (ISS) influence astronauts’ sleep patterns and alertness.

Why is this important? Astronauts perform intricate tasks that require focus and precision. If they are sleep-deprived or poorly adjusted to their environment, mission success and safety can be compromised. Light is a powerful cue to the human body, capable of shifting circadian rhythms. The experiment involved wearing actigraphy devices—wrist-worn monitors that measure movement and ambient light exposure. These devices collected data to track sleep duration and quality, wake times, and exposure to different wavelengths of light.

Researchers aimed to determine whether adjusting the lighting environment could help astronauts sleep better and maintain their mental performance. For instance, switching to blue-enriched light during waking hours and dimmer, warmer tones before sleep may support healthier circadian rhythms. The findings not only contribute to spaceflight safety but also inform the design of lighting systems in future spacecraft and habitats.

This research has broad Earth-based implications too. Shift workers, frequent travelers, and hospital patients could all benefit from what we learn about managing light to improve sleep health.

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