Light exposure during sleep impairs cardiometabolic function.
Level 2 - randomized trial
Controlled laboratory experimental trial in healthy adults
PubMed 35286195 · doi:10.1073/pnas.2113290119
What was done
Healthy adults were evaluated in a controlled laboratory study comparing the effects of one night of sleep under moderate light (100 lx) versus a dimly lit environment (<3 lx). Outcomes measured included nighttime heart rate, heart rate variability (sympathovagal balance), and next-morning insulin resistance.
What was found
No quantitative values or confidence intervals are provided in the abstract. Moderate light (100 lx) during sleep increased nighttime heart rate, reduced heart rate variability (higher sympathovagal balance), and increased next-morning insulin resistance compared to dim light (<3 lx). Higher sympathovagal balance positively correlated with morning insulin levels.
Why it matters
This study provides experimental human evidence that acute nighttime light exposure directly activates the sympathetic nervous system and disrupts morning metabolic homeostasis.
Limits
The abstract does not disclose sample size, demographics, or exact numerical effect sizes. As an acute single-night laboratory experiment, the long-term clinical consequences, habituation effects, and impacts across diverse clinical populations remain unmeasured.
Cited by
- supports A study published in the Proceedings of the National Academy of Sciences showed that sleeping under 100 lux overhead light compared to dim light elevates morning blood glucose.