Working at night is the biggest challenge to the human
circadian system, as we are simply not designed for it.
It’s tempting to seize on high-intensity lighting that
mimics daylight as the solution to keeping night-shift
workers awake and functional. It is certainly true that
exposure to light at night suppresses the production of
melatonin – the hormone that tells the body to sleep,
and the more intense the light, the greater the effect.
This coincides with feelings of alertness and higher
sustained attention. But scientists warn that messing
with melatonin too much can disrupt people’s sleep-wake cycle and harm their health in the long term.
Electric light in classrooms definitely has an effect on
the physical and mental health of students, particularly
in rooms with little daylight. Studying under brighter,
colder light in the morning can boost academic
performance, improve social behaviour, influence
physical health and help banish sleepiness.
Three Dutch studies looked at the educational
performance and concentration level of school pupils
working under 93 foot-candle, 1000 lux cold white
(6500K) lighting. The children’s performance was
compared with control groups working under 56
foot-candle, 600 lux (4000K) and 35 foot-candle, 380
lux (3000-4000K). All three studies reported fewer
errors and improved performance among the pupils
in the experimental group. Only two found improved
Another study compared the oral reading fluency of
seven and eight-year-olds under standard lighting
( 47 foot-candles, 500 lux, 3500K) and brighter, colder
lighting ( 93 foot-candles, 1000 lux, 6500K). Pupils in
the bright light group started with a lower score but
ended with a much higher score than the others.
There is evidence that the absence of blue light during
the school day delays the circadian clock. In one study,
11 adolescent students wore orange glasses throughout
a five-day school week to exclude blue from the ambient
light. The effect was to delay the onset of melatonin (the
start of the sleep-wake cycle) by 30 minutes.
It is known that disrupting the body clock can cause
underperformance in exams and academic work. A
study of 132 university students found that those with a
disposition to wake early and go to bed early tended to
achieve better grades compared with night owls.
There is plenty of evidence to suggest that people feel
In the workplace, the amount of lumens emitted by a light may be less
important than its effect on our daily biological rhythms. Biodynamic
lighting – such as this installation at AstraZeneca’s facility in Cheshire,
England – sets out to exploit this phenomenon