Bright Days and Dark Nights Extend Lifespan by Five Years

Key Quotes

"We found that people exposed to the brightest nights had a 21 to 34 higher risk of premature mortality whereas people exposed to bright days had 17 to 34 lower risk of premature death so basically what they saw was a dose response relationship meaning you know as your night got brighter the higher risk of dying in the coming years and then the brighter your days were the less your risk of dying was."

Daniel Windred, a postdoctoral researcher, explains the study's findings on light exposure and mortality risk. This quote highlights a direct correlation between the intensity of light exposure at night and an increased risk of premature death, while brighter daytime exposure is associated with a reduced risk. The concept of a "dose-response relationship" is introduced, indicating that greater exposure to bright light at night leads to a proportionally higher risk.

"This is a very exciting milestone thinking back to nearly 40 years ago when we first discovered that light was the most powerful synchronizer of human circadian rhythms that was incredibly controversial and disputed to come full circle to the recognition that not only is light the most powerful synchronizer of our internal circadian clock but keeping our clock in sync with the 24 hour day is critical for our health and wellness and longevity."

Dr. Charles Czeisler, a researcher at Brigham and Women's Hospital and Harvard Medical School, reflects on the scientific journey of understanding light's role in circadian rhythms. This quote emphasizes the historical significance of recognizing light as the primary regulator of our internal biological clock and underscores its critical importance for overall health, well-being, and lifespan.

"The key point here is that we have these circadian rhythms and I'm sure you know folks have heard about this before these are the patterns in our biology that fluctuate you know approximately over the 24 hour cycle they have enormous influence on our bodies on our hormones our blood pressure metabolism and this circadian machinery is really all throughout our body it's in our organs it's in our cells but the central timekeeper the kind of orchestrator if you will is in the brain in a region called the suprachiasmatic nucleus and this region in the brain responds very powerfully to light."

Will Stone explains the fundamental concept of circadian rhythms and their pervasive influence on bodily functions. This quote clarifies that these rhythms are not confined to a single area but are a body-wide biological process, with the suprachiasmatic nucleus in the brain acting as the master regulator that is highly responsive to light cues.

"Lots of research including these carefully controlled lab experiments show that inappropriately timed light can be hazardous it's linked to mental illness cancer especially metabolic and cardiovascular driven diseases like diabetes heart disease and obesity."

Will Stone connects the disruption of circadian rhythms due to light exposure to a range of serious health issues. This quote lists specific health consequences, including mental illness, cancer, and metabolic and cardiovascular diseases, underscoring the hazardous impact of mistimed light exposure on physical and mental health.

"The first thing is simply make sure you're getting outdoors during the day and getting the light in that context because the light outdoors is stronger... there's a kind of orders of magnitude difference between indoor and outdoor environments typically and so as long as you can prioritize daylight getting outside that will help."

Will Stone provides a practical recommendation for managing light exposure by emphasizing the importance of daytime outdoor activity. This quote highlights the significant difference in light intensity between indoor and outdoor environments, suggesting that prioritizing time spent outside is a key strategy for obtaining beneficial daylight exposure.

"The bottom line is the darker your night the better you will be... the people who had the lowest chance of dying in the coming years were exposed to you know what Windred described as barely any light between about midnight and 6 am so quite dark on the other hand the people who had bright light during the middle of the night and specifically they found kind of between 2 30 and 3 am that was associated with the highest risk of mortality."

Will Stone reiterates the importance of dark nights for health outcomes, referencing Windred's findings. This quote contrasts the health benefits of minimal light exposure during nighttime hours with the increased mortality risk associated with bright light exposure in the middle of the night, pinpointing a specific time window of heightened sensitivity.