Damned Lies and Statistics – and lighting = electric windows…

“There are three kinds of lies: lies, damned lies, and statistics.”

Lies, damned lies, and statistics

How do you know if applied lighting research results are valid?

Veitch et al ask this important question in this brilliant paper, using the celebrated Kruitoff Curve to demonstrate her argument: Kruithof proposed that we prefer bright lights to be ‘cool’ and dim lights to be ‘warm’, a link that is ‘common knowledge’ in the lighting sector.

But, perhaps unsurprisingly, the methodology in this 1941 paper falls far short of modern standards: for example, there is no clear hypothesis or information about other light sources or configuration of the room, time of day, duration or even the number, age or gender of participants. The outcome, ‘preference’ is equally flawed as it poses the question, compared to what – and what for? – Judging the Scientific Quality of Applied Lighting Research.

Fotios reviewed Kruitof-type evidence and found no evidence of this link – simply that people generally don’t prefer dim lighting – A Revised Kruithof Graph Based on Empirical Data.

That doesn’t mean we shouldn’t look for evidence of impact in the real world, but we do need to take a critical view. Veitch offers a valuable checklist for researchers and readers alike: Overall, is the paper clearly written and structured? Does the methodology account for critical variables, including sample size and profile? Does the evidence support the conclusions?

Although it’s tempting to seek out the flashy result, it’s just as important to note that nothing happened at all.

Quiz time 

Everyone likes a quiz. Here are three measures commonly used to test acute non-visual effects of light – try them yourself – you can even tell your boss you’re working 😉

Psychomotor Vigilance Test 

Measures your alertness and ability to maintain consistent attention over prolonged periods of time – Objective and Subjective Measurement of Excessive Sleepiness, Psychomotor Vigilance Test.

Reaction time –

Measures time between stimulus and response– Reaction time test.

Working memory –

The ability to hold information for recall, manipulation or recombination and decisionmaking, sometimes related to ‘fluid intelligence’ – Is the n-back task a measure of unstructured working memory capacity? Towards understanding its connection to other working memory tasks – try this one on the Psytoolkit website – lots of other cool experiments on there too – N-Back task / 2-Back task.

“Circadian lighting – like electric windows on a car. Manual windows are fine –  but once you’ve had electric ones, you don’t want to go back!” 

It can be hard to justify the cost of a lighting upgrade, especially in the cash-strapped Residential Care sector.  After all, current guidelines – the Lighting Guide for Communal Residential Buildings (LG09:2022) – simply require basic light levels for visual comfort at 300 lux-  significantly lower than office standards EN12464-1 and no mention at all of circadian lighting.

And yet, some care home managers do just that.

David Poxton, the third generation to run the Ashmere Care Home family in Derbyshire, estimates that the circadian lighting solution added around 40% to the cost of a basic retrofit.

David worked with a lighting manufacturer (Circadacare) to design a fitting that would deliver the quality and quantity of light they needed but keep a domestic look and feel.

The main battle was to get the installers to deliver the specification, prompting Circadacare to design a simple ‘plug and play’ retrofit luminaire for future installations.

This was part of a wider initiative to create a calm, peaceful environment at night that includes black-out curtains and acoustic monitoring inspired by a visit to WCS Care.

This integrated approach means that staff can monitor residents from a common area and bring residents who can’t sleep to a ‘wide-awake’ club, leaving bedrooms and corridors completely quiet.

Was it worth it?

David is clear that this was money well-spent:

“Lighting was not the most expensive item on the shopping list, and the households are more settled, especially in the evening. This has a ripple effect on staff well-being, too.”

David points out that, for staff arriving for the evening shift, the evening is the start of their day, so they tend to bring a ‘wide awake’ morning energy just when the residents need to wind down for bed. The softer evening light setting seems to help the staff to adopt that calmer attitude, easing that transition into sleep.

In David’s view, circadian lighting “is how things should be…”

“Like electric windows on a car. Manual windows are fine, but once you’ve had electric ones, you don’t want to go back!”

Please join us on the 5th of September to hear from other pioneering care home providers about why they’re not going back to manual windows either! – Innovators in Healthcare.

And if you’re in the East Midlands, please come to the Innovations in Healthcare event on the 11th of September in Uttoxeter – more information is here.