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Circadian Rhythms

Recognising the Circadian Rhythm in the workplace.


WHAT IS THE CIRCADIAN RHYTHM?

The Circadian rhythm sets the body’s natural clock and regulates the sleep/wake cycle.

It is controlled by the level of melatonin secretion in our bodies. When melatonin is released we will feel drowsy.

The Circadian Rhythm is close to being a 24 hour cycle but is not controlled by time. It is controlled by exposure to light and the colour temperature (CCT) of that light.

High CCT (6500K) light will suppress melatonin production and low CCT (3000K) light will encourage melatonin production.


On a normal day, the daylight will naturally expose us to the correct light levels for optimum melatonin production.

Problems in our sleep/wake cycle occur when we are not exposed to enough natural light and when we are exposed to too much artificial light (at a high CCT) at the wrong time of the day.

This can affect sleep quality, productivity, memory and cause serious health problems.


YOU KNOW THAT GOOD LIGHTING MAKES YOU FEEL BETTER AND A SUNNY DAY IS SO MUCH NICER THAN A GREY DAY. YOU MAY KNOW HOW UNPLEASANT CIRCADIAN DISRUPTION FEELS, YOU JUST PROBABLY CALLED IT JET LAG.

Mariana Figueira Ph.D from the lighting research center states:

"We can now quantify how the spectrum of light, the light level at the eye and the timing of light exposure can be used to synchronise your circadian rhythms or shift the timing of your sleep. To entrain your circadian rhythm, get high circadian stimulus in the morning with bright blueish/white light and low circadian stimulus in the evening with dim yellowish/white light. A well entrained circadian rhythm allows you to sleep well at night and feel alert during the day. "

WHAT IS THE CIRCADIAN STIMULUS (CS) METRIC?


This is the type and intensity of the lighting needed to suppress the hormones that make us feel sleepy.


Research with Alzheimer’s disease patients, office workers, teenagers and healthy older adults shows that exposure to a CS of 0.3 or greater at the eye, for at least one hour in the early part of the day, is effective for stimulating the circadian system and is associated with better sleep and improved behaviour and mood.

WHAT IS WRONG WITH CURRENT LIGHTING TECHNOLOGIES?

Up until 200 years ago, humans spent much of their time outside. Today, humans spend 90% of their time indoors with artificial lighting.

Current lighting technologies emit a fixed colour temperature.

This essentially ‘hacks’ your circadian rhythm and can affect your sleep and energy levels.

Working in an office, school or travelling can affect your circadian rhythm because you are not being exposed to natural levels of light at the correct times of the day.


CIRCADIAN RHYTHM IN THE WORKPLACE

We can combat these issues caused by artificial light affecting our natural circadian rhythm by using circadian lighting.

Circadian lighting mimics natural daylight by automatically adjusting the CCT to the optimal level for the time of day.

In the morning it will provide maximum levels of blue rich/cool white light that will signal to the body that it is daytime.

Later in the day it will automatically reduce the light levels and change to a warm glow which tells your body it is night time and stimulates melatonin production.

WHAT ARE THE BENEFITS OF CIRCADIAN LIGHTING?

There are so many benefits to using circadian lighting and regulating your circadian rhythm:

  • Improved sleep

  • Drives natural eating times

  • Increased productivity and concentration

  • Improved mood and energy levels

  • Improved memory and cognitive processing

  • Relaxed feeling in the evenings

  • Reduced dementia symptoms, risk of cardiovascular disease, obesity and diabetes

So many people would benefit from the use of circadian lighting:

  • Office workers

  • Elderly people

  • Schools

  • Jet lag sufferers

THE CIRCADIAN LIGHTING DESIGN PROCESS


Lighting for the circadian system is quite different from traditional architectural lighting design. Generally speaking, the latter approach has focused primarily on visibility and related concerns such as reduction of glare and shadow, colour rendering, safety and the appearance of the space.


When specifying lighting for the circadian system, it is important to consider light level, spectrum (colour), timing and duration of exposure, and photic history (previous light exposures).

When specifying lighting for the circadian system, it is important to consider light level, spectrum (colour), timing and duration of exposure, and photic history (previous light exposures).



If possible, designers should perform on-site field visits to evaluate the space’s current lighting conditions.


Designers should first decide on the design objectives—that is, whether they want to achieve entrainment or acute alertness—and then formulate a base condition by evaluating the space.


This can be done using the Circadian Stimulus (CS) metric which identifies the lighting needed to suppress melatonin. A CS calculator has been developed to allow for calculations to be made ensuring proper circadian light exposure at the right time.

Once this is established, designers will have a solid footing for selecting new luminaires, creating a lighting plan, tuning the light in terms of spectrum and light level, and formulating a dosage schedule over the course of the day.


The design can be fine-tuned using the CS Calculator, then remodelled and adjusted as necessary while also accommodating IES recommendations, energy codes and any client workspace specifications.


In an ideal world, decision makers and designers would be free to propose extensive redesigns with new tuneable luminaires programmed to deliver customised CS dosage schedules (Figure 5). But designing with CS to achieve healthy outcomes doesn’t have to break the bank. In situations where renovations may be impossible due to budgetary or architectural constraints, low-cost and low-impact solutions can be established.

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