Light (Links With Sleep)

· For most of our history, time has been determined by the solar cycle, ie we evolved to spend hours outside every day; with bedtime coming soon after sunset when the sky was black. Now most of us pass our waking lives inside offices, factories, schools, hospitals, shops, nurseries, etc away from natural light in poorly lit rooms with sealed windows. Once day begins to fade, we flick the switch and light returns. Compared with our ancestors, our working hours are gloomy and our nights dazzling!

· There is a link between light and health. For example, over the last few decades, medical professionals have warned us about the negative impacts of ultraviolet rays in contributing to skin cancer. More recently, there is concern that too little daylight can have long-term damage on your health. By overriding the light-dark cycle of the natural world, we could be disrupting the internal workings of the human body. One consequence is that we sleep less. Most young adults sleep for about 8.5 hours per day (one third of us have 6 hours or less); this is 20% less than a century ago (United States National Sleeping Foundation). Furthermore, most of our children are sleeping around 75 min less each school night than a century ago. Whereas tired adults become sluggish and lethargic, kids become hyperactive and distracted. This may explain the increasing number of children who are now diagnosed with "attention deficit hyperactive disorder" (ADHD), ie 1 in 10 children in USA. ADHD symptoms are remarkably similar to those of sleep deprivation.

· Being tired makes us less productive, more forgetful and apt to make mistakes. For example, human error in the early hours of the morning contributed to the Exxon Valdez oil spill and nuclear accidents at Chernobyl (Russia) and 3 Mile Island (USA).

· Research is showing that in brighter environments, we are more alert, complete visual tasks better and make fewer mistakes

· Our bodies respond to light

- gloomy winters' days are known to trigger a form of depression (seasonal affective disorder - SAD); this can be reversed by exposure to light

- bipolar patients in east-facing hospital rooms stayed almost 4 days fewer than those in west-facing ones

- people recuperating from spinal and cervical cancer in bright rooms took fewer painkillers

- female heart attack patients treated in intensive care units recovered faster if they were exposed to plenty of natural light

- mortality is consistently higher in dull rooms (Rosie Blau, 2014)

· Light impacts our body clock.

i) even if we are kept in the dark, we still wake and sleep at precise intervals over a 24 hour period; this indicates that an internal clock controls the sleep-wake cycle, ie circadian pacemaker. It also responds to the environment, especially light and dark.

ii) some types of light have more impact than others. Our eyes see 3 main colours of light, ie red, green & blue, with each working at different wavelengths. In the morning, high concentrations of blue occur naturally; by dusk we are left mostly with green and red. The blue light has the greatest impact on our circadian clock, ie informing the brain that it is morning, time to be alert and setting the clock for the rest of the day.

iii) our brain and body function better if the internal signals of the body clock are synchronised with the external cues of day and night.

iv) unfortunately, artificial light does not represent the same colours of the natural world. Most electric light has a high intensity of blue which deceives the brain into thinking that it's day when it is not. Just 10 minutes of regular electric light can make some changes to our internal clock.

"...We have evolved to be blue sensitive, we need...... many of us get a tonne of it, particularly in the evening when we get home. We spotlight the kitchen so we can make dinner, then plug into our laptops smart phones bringing blue light into our eyes at close range. So we bombard our internal clock with mixed messages: they are gloomy morning sends a weak signal to be alert; our overbright evening shouts at our brain to rise and shine. We also have less than contrast between light and dark that our circadian system relies on the function. All of which makes us more prone to insomnia..."

Satchin Panda as quoted by Rosie Balu, 2014

Traditionally, we sleep during the night time. With development of electricity, we can turn night into day

. Research is showing that in natural light or brighter environments, we are more alert, complete visual tasks better & make fewer mistakes

. Don't confuse brightness with light, eg TV & some offices seems bright but have little light; an overcast day has plenty of light

. Trends in urbanisation, eg home, offices, etc mean that people are exposed to less natural light

. Daylight is not intrinsically better for us than electric light. It's just that getting artificial light to do the same job is more expensive, uses more energy & it is more difficult to get right balance

. Having a good night's sleep depends on having the right amount of light at the right time during the day, eg exercise outdoors in the morning

. We need more light to synchronise the circadian system than we do to see

. There are 3 types of light, ie

- blue

- green

- red.

Blue is important in the morning & to keep us awake; while green & red at dusk encourage sleep

. Unfortunately, artificial light does not represent the same colours of the natural world; it has too much blue which is harmful at night.

. This blue light is generated from screens (computer, iPads, etc), bright lights, etc and suppresses melatonin (sleep-promoting hormone). Thus these are OK to view in the mornings but a problem at night time

. Sleep disturbances magnify as we age. Most people over 65 have serious problems going to sleep, waking up often at night or struggle to keep their eyes open during the day.

. Disrupted sleep is linked with declining physical condition and immunity

. We need more devices that are circadian-friendly, ie programmed to radiate less blue light in the evenings & more in the mornings

. In addition to light & dark, the body clock responds to the direction of rays & movement in a scene

12 tips to better handle light & sleep

    get up and go to bed at the same time every day
    let natural light into your bedroom when you get up
    maximise time in the sunlight
    keep blinds/curtains open that are near to your desk
    work near a window
    play video games by day, not at night
    buy an extra desk lamp
    eat dinner with the lights dimmed
    don't use your computer or tablet for 2 hours before bedtime
    reduce blue glare from your computer
    make your bedroom dark or wear a facemask
    turn off the lights half an hour earlier

· Food can help synchronise a biological clock

· More research is required on life to determine

- How much light do we need?

- Does it matter if the light is natural or electric?

- Does getting lots of light on one day compensate for less on another?

- What could be the long-term impact of spending days in "dark" rooms?
In summary (linking energy, water, sleep & light)
Lack of energy and/or water and/or sleep and/or inappropriate lighting impacts adversely on executive functions, eg

- making poor decisions

- choosing impulsively

- being cranky

- struggling with problem solving/memory tasks

- being more susceptible to negative health issues

. Ideally don't want an organisation of hungry, tired &/or thirsty people who don't breathe correctly and work in poorly lit workplaces !!!

(sources: James Hall, 2004d; Brad Hatch, 2005b; Sora Song, 2006; Robert Winston, 2003: Fiona Smith, 2006b; Susannah Moran, 2006; Charles Czeisler, 2006; Alexandra Roginski, 2012; Rosie Balu, 2014)