safer under bright light at night. High levels of uniform
lighting provide greater visibility and reduce road
accidents. However, good lighting conditions might also
make drivers inclined to drive faster. Pedestrians like
lighting that makes them easily visible to drivers and
helps them recognise faces.
Lighting that clearly illuminates the surroundings
provides reassurance and discourages crime. But light
pollution is a serious issue, and what is seen as pleasant
by some might be seen as pollution by others. Exposure
to light at night has been associated with cancer and
lower cognitive performance. Nocturnal lighting
harms the wellbeing of some animals, interfering with
reproduction, orientation and hunting.
People might like bright streets, but they also need the
downtime of darkness to restore their bodily health
during the night. A subtler approach to lighting the
nightscape might pay dividends.
Since short wavelength light has the strongest impact
on circadian cycles, light sources with limited blue
emissions are being developed for use after dark.
Domestic lighting has a significant impact on our
wellbeing. Lighting that triggers the ‘wrong’ response in
our circadian clocks can make it harder to drop off to
sleep at night and wake up feeling alert and refreshed.
LED technology has the potential to work with our
natural rhythms while keeping energy bills down.
Generally speaking, the more blue-enriched the light
source, the more alert and wakeful we are likely to feel.
Most homes, of course, are filled with gadgetry such as
TV sets, smartphones and laptops, all of which emit
blue-enriched light. This should be taken into account
when designing lighting for private homes.
Conventional indoor lighting is unhelpful when it
comes to winding down for sleep; any lighting in the
evening interferes with the body clock. Even low to
moderate intensity light ( 4-23 foot-candles, 40-250 lux)
can suppress melatonin, delay sleep and make us feel
more alert. The more blue the light, the stronger the
effect. Recent studies have found a positive correlation
between insomnia in older people and light levels in the
evening and at night in the bedroom.
In the morning, our bodies are programmed to
wake gradually in response to warm dawn light. Our
cognitive processes are generally fuzzy at first, but as
the sun moves across the sky the cooler blue daylight
helps us feel more alert. Research shows that waking
up in blue-enhanced white light conditions can have a
beneficial effect on cognitive processes such as short-term memory throughout the day.
Lab tests have found that exposure to moderate intensity
light in the morning changes the circadian system,
bringing forward the onset of melatonin and therefore
altering the sleep-wake cycle. In one study, two hours of
light stimulation on two consecutive mornings using a
blue short wavelength (470nm) LED advanced the onset
of melatonin by over one hour.
All of which suggests that smart domestic lighting
functioning in tune with our natural rhythms rather
than fighting them should find a ready market. However,
scientists warn that we need to know more about the
body’s response to light of differing intensity and
wavelength before we can design dynamic light settings
for the home that have the intended effect. Age, gender
and even genes may all play a part in the way sleep-wake
regulation works, and should be fully explored.
As we grow older, our vision is reduced and the amount
of light that enters the retina and tells the body what
time it is decreases too. Add to that the many hours
spent indoors once we’re no longer mobile, and the
potential lack of adequate light in care homes, and it
becomes clear that there is a gap of light intake that new
lighting technology can attempt to fill.
Some studies have shown a link between light therapy
and improved night-time sleep in nursing homes, but
the body of evidence is not yet considered strong enough
to conclude that improved biodynamic lighting can help
the elderly stay in tune with their circadian rhythm.
While the evidence is ambiguous in the case of elderly
people, it is clearer when it comes to people suffering
from depression. Research shows that strong light
therapy of 930 foot-candles ( 10 000 lux) applied in
the morning alongside antidepressant drugs such as
sertraline and citalopram increases the effects of the
drugs. The level of the light appears to make a difference
in both chronically depressed patients and patients with
seasonal affective disorder (SAD), where light of 560
foot-candles (6000 lux) has proven to be more effective
than 163-280 foot-candle (1750-3000 lux) and 56 foot-candle (600 lux) alternatives.
Tunable LED light for patient rooms, mimicking the
gradually changing light on a sunny day, have started
to appear on the market. A study shows that patients
exposed to one such system slept longer, took less time
to fall asleep and scored lower on the depression scale
than patients exposed to the existing light.
‘There are few real-world solutions that
successfully combine an understanding
of the physiological effects of light with
efficiency and aesthetics’