Outdoor night light exposure and sleep structure, a panel study using consumer-grade wearables

Area of Science:

• Environmental Health
• Sleep Science
• Public Health

Background:

• Artificial light at night (ALAN) is a growing public health concern.
• ALAN can disrupt circadian rhythms and negatively impact sleep quality.
• This study investigates the link between outdoor nighttime light (NTL) and sleep duration.

Purpose of the Study:

• To examine the association between outdoor NTL exposure and objectively measured sleep duration.
• To identify potential demographic or behavioral factors influencing this association.
• To inform urban lighting guidelines for better sleep health.

Main Methods:

• Utilized wearable device data (Zepp Health smart bracelets) from 4,690 Chinese participants (2017-2019).
• Assessed outdoor NTL exposure using NASA's Black Marble product.
• Employed mixed-effects regression models, adjusting for covariates, to analyze NTL and sleep metrics.

Main Results:

• Increased NTL exposure correlated with a slight increase in light sleep duration (1.22 min per SD increase).
• No significant linear association was found between NTL and total or deep sleep duration.
• Subgroup analyses indicated stronger associations in the elderly, lower BMI, non-drinkers, smokers, and those in lower-income areas.

Conclusions:

• Moderate NTL levels may slightly increase light sleep, while higher levels might reduce deep sleep.
• Findings highlight the need for urban lighting policies balancing safety and sleep health.
• Emphasizes the importance of considering individual sleep behaviors and indoor light exposure in future research.