Life Kit How to optimize your circadian rhythm
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Dec 4, 2025 
In this enlightening discussion, Will Stone, an NPR health correspondent known for his insightful analysis on health, dives into the critical role of light in our lives. He shares intriguing findings from the UK Biobank study linking light exposure to longevity. With practical tips, Will emphasizes the importance of getting at least 45 minutes of daylight while keeping nights dark. Reducing nighttime light exposure and using orange nightlights can further enhance our circadian rhythms, promoting better sleep and health.
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Host's Real-World Light Struggle
- Marielle describes her fight to make her bedroom pitch black despite blackout curtains and streetlight intrusion.
- She notes light sneaks under doors and around shades, a common real-world disruption to sleep.
Large Study Links Day/Night Light To Longevity
- Researchers tracked ~90,000 UK Biobank participants with wrist devices that recorded light and activity over years.
- Brighter days associated with lower mortality while brighter nights associated with higher mortality in a dose-response pattern.
Correlation, Not Proof — But Compelling
- The study shows correlation, not proof of causation, but controlled for many confounders like income and health.
- Even after adjustments, the clear pattern remained: bright days good, bright nights bad.