Korva is a scroll of the internet’s best ideas.
Night-shift workers live shorter lives, cancer rates go up, and they are metabolically unhealthy, and it is very hard to mitigate. The studies behind those findings, apart from the more extreme ones, mostly looked at people after 6:00 PM who were on devices getting artificial LED exposure or doing anything besides eating, socializing with family, or being in bed.
A large UK Biobank study found that bright days and dark nights add together. Bright days improve mental and physical health along a huge number of parameters, and dark nights make people healthier even after dim days. The risk of dying early goes up immensely with bright nights.
Screens are not nearly bright enough to kickstart the morning cortisol rise, but they are bright enough to raise cortisol at night, when low cortisol leaves a person vulnerable to big increases.
Who decided night shift might cause cancer?
In 2007, the International Agency for Research on Cancer, part of the World Health Organization, classified shift work involving circadian disruption as probably carcinogenic to humans, in Group 2A. The 2019 review kept that classification. The evidence came mainly from studies of nurses and other night workers, and from animal experiments. The agency ranks the strength of evidence for causing cancer, not the size of the risk.
Why does light at night suppress melatonin?
Retinal cells that contain melanopsin send light information to the brain's master clock, which in turn controls the pineal gland. These cells respond most strongly to blue light near 480 nanometers. In a 2001 study by George Brainard and colleagues, melatonin suppression peaked at about 460 nanometers. That is a color rich in LED screens and white light bulbs.
How did researchers measure light exposure?
A 2024 study in PNAS led by Daniel Windred at Monash University used data from about 89,000 UK Biobank participants. Each person wore a light sensor on the wrist for a week. Researchers then followed their health records for around eight years and compared light patterns with deaths. People with the brightest nights had a higher risk of dying in that period.
More from The Diary Of A CEO with Steven Bartlett
