March 28 2019
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The impact of light on healthcare operations

This article explores the impact that environmental factors such as light have on healthcare and considers how they can be optimised to support patient and staff well-being.

Behavioural outcomes influenced by lighting

Lighting can have a profound effect on the way that people behave. Lighting can alter mood, level of fatigue, resilience to shift patterns and stress. From a patient perspective, lighting has been shown to reduce recovery time– it has been shown to be beneficial in terms of affecting sleep-wake disturbances, mood and pain. Lighting also impacts on the use of medical equipment. At a very fundamental level, the user needs to be able to see the equipment and read the display in order to operate it safely and effectively. In a similar way, there are many surgical and diagnostic tasks that benefit from controlled and stable illumination so that the correct decisions are made. The upshot of the above is that one simple intervention (changing a light bulb) can have a profound impact – this article explores why.

Consumer benefits of optimised lighting

There are many reasons to optimise lighting levels from a human factors perspective. For example, the level of the ambient (e.g. the properties of the light used to illuminate the room) has been shown to impact on alertness and fatigue – it has been shown to impact on quality of work life. It follows that there can be a negative impact in that dimly lit environments can increase feelings of sleepiness, lack of energy and contribute to poor focus. At the same time, although there can be a benefit in higher levels of illumination in terms of increasing alertness and avoiding fatigue – high levels also have the potential to increase cortisol levels (stress). This relationship interacts with colour temperature and varies across gender and age. Specifying optimal ambient lighting is therefore far from trivial.

Image credit: Stock

To explore this situation we took measurements of ambient illumination in a local hospital. This was part of an “observational” – a type of study where (design) researchers move out of the controlled, lab-based environment and move research into context to benefit from the ecological validity that can be provided.  During a series of observational studies at a local hospital, this is exactly what we did, testing a handheld spectroscopy unit powered by a smartphone for quick and accurate spectral light characterisation. The device could measure key parameters such as lux, CRI, CCT – it could also sample measurements over time. We did this to understand more about the types of light present in this environment and consider ways in which the lighting may impact (both on the quality of work-life and the use of medical equipment). We collected a series of measures – relating to illumination sources within an operating theatre environment (including the ambient illumination).

The device that we used took measures of CRI. The Colour Rendering Index (CRI) is a measure of the ability of a light source to reveal the colours of various objects – it is calculated based on how well a light source renders a series colours. We measured CRI (and CCT) and found that the R9 level associated with the ambient was comparatively low (about a tenth of what might occur in natural light). R9 relates to the extent to which an illumination source reveals red. R9 is associated with seeing skin tones, blood and tissue. It is also associated with the legibility of anything that is printed in red.

Image credit: Wave Illumination

Why this matters

There is a reason to believe that behaviour could be impacted by a lack of R9. Lab-based studies have shown an impact of the removal of stimulus chromaticity. This is particularly the case for red-green colour, the removal of which differentially impacts visual object recognition ability. The explanation for this has its roots in evolutionary theory.  More generally, there is a range of findings demonstrating an impact of the colour of light on human performance. For example, colour can impact short-term memory and problem solving – people perform better in `warm’ rather than `cool’ and artificial `daylight’ white lighting. Females and males have been found to show differing levels of positive and negative mood based on illuminance and/or CRI levels.

How to apply this knowledge 

One way that we can consider the impact of lighting is to take regular surveys of the environment and tailor the light in line with accepted norms and conventions. Certain areas in the hospital may need to be prioritised – surgical areas and pharmacy environments for example. Across the hospital as a whole there are many benefits to be realised – for example:

  • The usability of equipment can be improved through considering the properties of the illumination (e.g. errors can be reduced).
  • The colour rendering potential of various light sources can have a clinical impact from the perspective of detecting jaundice, skin lesions, as well as for the use of various diagnostic tests. There are also various therapeutic benefits.
  • Night-shift staff may be in a better mood if they are working under light shifted towards red, rather than blue or white light. There is potential to consider varying the properties of illumination to support shift work.
  • For inpatients – lighting can interact with recovery time – mental health patients staying in sunny rooms have been found to recover faster: (an average stay of 16.9 days for sunny rooms compared to 19.5 days for those in dull rooms). Patients may recover faster if they have access to daylight.
  • Ultraviolet lighting appears to be an effective way to lower the risk of infection in the operating room during total joint replacement surgery. Light can be used to provide very specific clinical benefits.

Image credit: Stock


We set out to explore the impact that environmental factors have on healthcare settings and consider how these factors can be optimised to support patient and staff well-being. We found that there was an opportunity for changing the light to provide benefit – for example shifting the colour temperature or raising / lowering the luminance. Hospitals can therefore get more out of the resources that they have by considering the design of the environment (e.g. happier, productive staff, less mistakes, faster throughput).

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Posted by Chris
Principal – Human Factors & Ergonomics, Sector lead Healthcare

Languages spoken: English (native).
The last thing that inspired me: Seeing the London Air Ambulance land.
My dream project: A medical tricorder.
My obsession: Running.

Image credit Stock, Wave Illumination