Are you a night shift worker without knowing it?

What did Huberman actually say?

In a clip from The Diary of a CEO, the Andrew Huberman episode of 3 September 2026, he says that night shift workers live shorter lives, get more cancer and are metabolically worse off, and that you and I qualify as night shift workers because the studies counted anyone on a screen with LED light after six in the evening. He adds that daylight late in the day buffers the cells of the eye against artificial light at night, that teenagers cannot be buffered, and that the problem with evening screen light is blood glucose and next-morning cortisol rather than whether you fall asleep. The clip is everywhere right now. We went to the studies.

What do the night shift studies actually show?

The largest source is the Nurses' Health Study, in which 74,862 American nurses were followed for 22 years. Those who had worked rotating night shifts for 15 years or more had 11 per cent higher all-cause mortality and 23 per cent higher cardiovascular mortality than those who never had (Gu et al. 2015, American Journal of Preventive Medicine). In the same cohorts the risk of type 2 diabetes rose with the years of shift work (Pan et al. 2011, PLOS Medicine), and in 2019 the WHO cancer agency IARC classified night shift work as probably carcinogenic, Group 2A.

So the numbers are real but less dramatic than the clip sounds: 11 per cent higher mortality after 15 years of night shifts, not a life cut in half. And the exposure behind them is years of night shifts, not evenings.

Does an evening in front of a screen count as a night shift?

Not in these studies. The Nurses' Health Study defines rotating night shift work as at least three night shifts a month on top of day and evening shifts. IARC defines night shift work as work during the hours when the general population sleeps. Neither counts the person at a laptop at nine in the evening. That sentence in the clip is a provocation, not a definition.

But the provocation points at something true. The night shift studies cannot show what causes the extra risk, and the researchers behind them point to the same mechanisms: light when the body expects darkness, food and wakefulness at the wrong hour, and an internal clock pulled out of phase. Scheer and colleagues tested that mechanism in the lab in 2009: ten people on 28-hour days, eating and sleeping twelve hours out of phase. Blood glucose rose 6 per cent despite 22 per cent more insulin, and three of eight had post-meal glucose responses in the prediabetic range. That is the full-scale version. The question is what the small dose, an ordinary evening in lamplight and screen light, does.

What does evening light do to ordinary people?

More than you would think, and it has been measured, not assumed. Ordinary room light under 200 lux in the eight hours before bedtime delayed the onset of melatonin in 99 per cent of 116 young adults and shortened the night's melatonin signal by about 90 minutes, compared with dim light under 3 lux (Gooley et al. 2011, Journal of Clinical Endocrinology and Metabolism). Four hours of reading on a lit tablet on five consecutive evenings gave 55 per cent lower melatonin, an internal clock shifted an hour and a half later and poorer alertness the next morning (Chang et al. 2015, PNAS). How that works is covered in Blue light and melatonin.

Blood glucose, which Huberman singles out, has been measured too. Three hours of blue-enriched light in the evening gave a higher peak glucose than the same people had in dim light, in 19 normal-weight adults (Cheung et al. 2016, PLOS ONE). A single night with 100 lux on in the bedroom raised heart rate during sleep and insulin resistance the next morning, compared with under 3 lux (Mason et al. 2022, PNAS). And in UK Biobank, where 88,905 people wore a light sensor for a week and were then followed for eight years, the ten per cent with the brightest nights had 21 to 34 per cent higher mortality than the darker half, while those with the brightest days had 17 to 34 per cent lower (Windred et al. 2024, PNAS).

Next-morning cortisol, which he also mentions, is where we found no controlled study for a single evening of screen light. Scheer saw the cortisol rhythm reverse under a twelve-hour shift, but that is not the same thing. We leave that part of the clip unsupported.

Is it true that afternoon daylight protects you?

In principle yes, and it is the most useful thing in the clip. How sensitive the eye is to light in the evening depends on how much light it got during the day. After a week with 4.3 hours of bright light a day, 500 lux at night suppressed melatonin less than after a week in dark goggles, in 12 people (Hébert et al. 2002, Journal of Pineal Research), and three days at 200 lux instead of 0.5 lux produced the same adaptation in the lab in eight (Smith et al. 2004). Closest to the clip's claim is a Swedish study from Uppsala: after 6.5 hours at around 569 lux during the day, two hours of reading on a tablet between 21:00 and 23:00 made no difference at all to melatonin or sleep compared with a printed book, in 14 people (Rångtell et al. 2016, Sleep Medicine).

Two caveats. The studies gave light across the whole day, not specifically in the late afternoon, so the exact hour is Huberman's reading of them. And the groups are small, 8 to 14 people, which the researchers point out themselves.

Why are teenagers a special case?

Because their eyes respond more strongly. Children in early puberty had melatonin suppressed 37 per cent by 500 lux in the evening, against 24 per cent in older teenagers, and the difference showed already at 15 lux (Crowley et al. 2015, Journal of Clinical Endocrinology and Metabolism). In nine-year-olds the suppression was almost twice that of adults, 88 against 46 per cent in a small group of five children and six adults, and ordinary home lighting of around 140 lux suppressed the children's melatonin but not the adults' (Higuchi et al. 2014). That they cannot be buffered by daylight, as the clip says, is something we found no study that has tested. That they are affected more by evening light is well established.

What do you do when the sun sets at three?

This is where Huberman's advice becomes a Swedish problem. The clip wants the daylight late in the day, but in Gothenburg the sun sets at 16:42 on 26 October, 15:58 on 15 November and 15:26 on 21 December. In Stockholm it is down by 14:48 at the winter solstice. The late-afternoon daylight does not exist, and the evening in lamplight and screen light runs six or seven hours. The table for six cities is in Winter daylight in Sweden.

• Get the daylight when it is there: a walk at lunch without glasses, on the days the sun sets before four.
• Turn the lamps down after sunset. Gooley's study shows ordinary room light is enough to push melatonin back.
• Filter what you look at anyway. Orange · Evening filters 98 % of blue light between 400 and 500 nm, Red · Night 99 % of blue and green between 400–550 nm. What that does to your melatonin we have not measured, only what the lens lets through.
• If you actually work nights: the lens is for the hours before bed, never for the drive home in the dark.

So no, you are not a night shift worker. But someone sitting in lamplight and screen light from half past three until eleven, five months a year, gets a small dose of the same thing every evening. That dose is what the evening is about. The evening hour by hour is in The evening routine.