Evidence: Dynamic light

Presented this week in Chicago, this paper shows how dynamic light that provides a high circadian stimulus during the day, and low circadian stimulus at night can lead to significantly decreased sleep disturbances, depression and agitation in participants with Alzheimer’s disease and related dementias compared with baseline. Furthermore, the positive effects observed in the short-term study continued to improve over the course of the 6-month, long-term lighting intervention.

Our circadian solutions are designed to deliver this variation in circadian stimulus automatically.

Monitored light intervention helps improve sleep in Alzheimer’s disease

Image of Mariana Figueiro

Mariana G. Figueiro

Daytime light — when carefully delivered and tailored to individual patients’ eyes and monitored with a calibrated instrument — can improve sleep, mood and agitation in nursing home residents with Alzheimer’s disease and related dementias, data presented at the Alzheimer’s Association International Conference revealed.

“The research is important because it is nonpharmacological,” Mariana G. Figueiro, PhD, director of the Lighting Research Center at Rensselaer Polytechnic Institute in New York, told Healio Psychiatry. “Being able to show the efficacy of a nonpharmacological treatment that helps Alzheimer’s disease patients sleep better, feel less depressed and improve their behavior is very much needed.”

Using a crossover, repeated-measures design, Figueiro and colleagues examined whether a tailored lighting intervention could improve sleep and behavior in patients with Alzheimer’s disease and related dementias living in long-term care facilities. Researchers exposed nursing home residents to alternating periods of lighting that provided either high- or low-circadian stimulus for 4 weeks (short-term study) and 6 months (long-term study, successive 4-week periods spaced by a 4-week washout), according to a press release.

The lighting intervention was added to places in which participants spent most of their time awake and was left on from wake time until 6:00 p.m. Calibrated personal light meters were used to monitor light exposures received in patients’ eyes. Using questionnaires, researchers assessed measures of sleep disturbances (Pittsburgh Sleep Quality Index), mood (Cornell Scale for Depression in Dementia) and agitation (Cohen-Mansfield Agitation Index) at baseline and during the last week of the intervention.

According to the release, 43 residents participated in the short-term study and 37 residents completed the long-term study. The results showed that the lighting intervention lead to significantly decreased sleep disturbances, depression and agitation in participants with Alzheimer’s disease and related dementias compared with baseline. Furthermore, the positive effects observed in the short-term study continued to improve over the course of the 6-month, long-term lighting intervention.

“Our study showed that light, when tailored to deliver the correct amount of circadian stimulus to the patient’s eyes, can be effective as an adjunct therapy to help Alzheimer’s disease patients sleep better, reduce their depression symptoms and agitation behavior,” Figueiro told Healio Psychiatry. “When properly prescribed and delivered, robust light-dark patterns can help Alzheimer’s disease patients improve sleep and behavior. But, it needs to be properly designed and delivered.” – by Savannah Demko


Figueiro M, et al. Tailored lighting intervention to improve sleep, mood and behavior in Alzheimer’s disease patients. Presented at: Alzheimer’s Association International Conference; July 22-26, 2018, 2018; Chicago.

Disclosure: Figueiro reports no relevant financial disclosures.

Sleep scientists say: Cyan is the key

This article tday published on the BBC news website includes comments from Professor Rob Lucas at Manchester University about the importance of the presence and absence of cyan to maintain your sleep cycle. Controlling the cyan content is at the core of our circadian lighting technology.


The colour cyan – between green and blue – is a hidden factor in encouraging or preventing sleep, according to biologists.

University of Manchester researchers say higher levels of cyan keep people awake, while reducing cyan is associated with helping sleep.

The impact was felt even if colour changes were not visible to the eye.

The researchers want to produce devices for computer screens and phones that could increase or decrease cyan levels.

Sleep researchers have already established links between colours and sleep – with blue light having been identified as more likely to delay sleep.

‘Night mode’

There have been “night mode” settings for phones and laptops which have reduced blue light in an attempt to lessen the damage to sleep.

But the research by biologists at the University of Manchester and in Basel in Switzerland, published in the journal Sleep, has shown the particular impact of the colour cyan.

Image caption Is cyan going to keep you awake?

When people were exposed to more or less cyan, researchers were able to measure different levels of the sleep hormone melatonin in people’s saliva.

Prof Rob Lucas said that it was not necessary for someone to be able to see the difference in colours, as the body reacted to the change even if it was not visible to the naked eye.

He said this could also affect other colours which were made using cyan.

For instance, there are shades of green that can include cyan – which also can be achieved using other colour combinations.

Screening colours

The researchers suggest that versions of the colour using cyan could be used on computer screens if the aim was to keep people awake – such as people working and required to stay alert at night.

Or there could be another version, the same colour but without cyan, which could be used if the aim was reduce disruption to sleep.

Image caption Researchers say the same colours can be created with or without cyan

The research used this with a movie – with the colours being adapted to include or exclude cyan – and found changes in viewers’ sleepiness and levels of melatonin in saliva.

The research team, headed by Prof Lucas and Dr Annette Allen, says there could be applications for this discovery on computer screens, televisions and smartphones.

“This outcome is exciting because it that tells us that regulating exposure to cyan light alone, without changing colour, can influence how sleepy we feel,” said Prof Lucas.

He said it might help families with teenagers who were using mobile phones at night-time.


A bit of history

PhotonStar have spent the last 10 years developing lighting that is better for people here in the UK. We first coined the phrase “circadian lighting” a decade ago, as we intoduced “SmartWhite” and “LEDSmart” – the very first dynamic lights and control system that delivered the right spectra of light for night and  a different optimised spectra for day.

This has been an exciting decade with the mass adoption of LEDs for energy saving, but also huge strides in the understanding of the non visual effects of light on our bodies and minds. In those 10 years, prices for regular LED lighting has dropped dramatically, but along with it a decline in UK manufactured LED technology that had reliability and quality at  its heart. The adoption by the majority of these low cost LED lights means that in most buildings now, the lights we use at light have too much blue content for our health.

Lighting control systems in the last 10 years have improved in leaps and bounds, but they are in the main focussed on saving energy or automating safety tests. PhotonStar has worked closely with the customers who benefit from circadian lighting to develop both a wired and a wireless solution that keeps the cost of providing circadian lighting to a minimum, and retains the simplicity of operation that our customers truly need. Just because technology can do lots of clever things – it doesnt mean it should.

The light sources, now almost all LED continue to be made using a blue LED and a yellow phosphor which together make white appearing light. By combining with controls – a tuneable white LED option has become popular, but it does not in any way provide a circadian solution as it provides too much blue light at night and typically not enough of the right blue during the day.

Our journey has been about making the technoogy fit the user, the application and the biology – which has taken us a little off piste compared to regular LED and controls products. Our light sources are developed for the human need for light and darkness. The control systems are designed for simple uncomplicated installation and operation. We realised several years ago that most people “just want a light switch that works and looks like a light switch”.  We also larned that by working with other product and service providers as well as the operations teams in care and healthcare to change ways of working, we could observe far better results.

This video was filmed in 2011 at the Rensellar Institute and talked about the understanding of non visual lighting needs as we understood them at the time.

Out of this world!

Light and darkness is key to the health, wellbeing and performance of people of all ages – not just our senior population.  At PhotonStar, we work with organisations who are looking to improve the health, cognition, happiness and sleep quality of their residents, students, employees and visitors. Some of our consultants however, have been involved in on of the most high profile circadian lighting solutions – the International Space Station.

Read more on the NASA website about why these rather unusual employees also need circadian lighting, and what is expected to be gained from it.

Light and Sundowning

Our circadian lighting solutions are designed to provide the best lighting for the time of day to help stabilise the body clock and reduce sundowning behaviours. It is well understood that not enough light in the day, and too much light at night contributes to sundowning issues. The challenge with conventional lighting is that the light levels need to be very high in the day to keep the body clock on track which can cause overstimulation or is just impractical. Our biologically optimised lighting provides a strong daytime trigger to the body clock without the need for excessively high light levels in the day. During the night, we may need lights to help with attending to night waking and prevent falls, so darkness, which would be the ideal, is not always a safe or practical option. Our system changes the light colour at night to provide night lighting that is spectrally optimised to keep the body in its darkness period, but provides enough light to see and be safe.

The alzheimers society provide the following guidance on sundowning:


Sometimes a person with dementia will exhibit an increase in certain behaviours in the late afternoon or early evening. For example, people may become more agitated, aggressive or confused. This is often referred to as ‘sundowning’. This pattern may continue for several months and often occurs in those in the moderate to severe stages of dementia. It can be particularly distressing for carers if they are trying to relax or have some quiet time.

Sundowning may be caused by:

  • disturbance to the 24-hour ‘body clock’ that tells our bodies when to sleep, caused by the physical changes to the brain
  • loss of routine at a previously busy time of day
  • too little or disturbed sleep
  • too little or too much light
  • prescribed medication (eg for pain or discomfort) wearing off
  • medications that worsen confusion and agitation
  • excessive or disturbing noise.

Using the term ‘sundowning’ may mean that people attribute out-of-character behaviours to dementia and overlook other factors causing the behaviour, such as someone trying to communicate. It is important to look at and address the potential reasons why someone is behaving out of character.

Sundowning – tips for carers

  • Try to give the person something meaningful to do at this time of day, using past activities as a guide.
  • Plan quiet and relaxing activities for late afternoon/evening.
  • Think about what’s happened during the day. Could the person’s behaviour be a communication of a need such as requiring the toilet, feeling hungry or being in pain?
  • Consider minimising daytime naps and make sure the person gets enough light, especially sunlight.
  • Exercise can be beneficial for helping someone to sleep.
  • Improving the environment can help someone to sleep better, as can reducing intake of caffeine and alcohol in the evening.
  • Keep lighting appropriate – if it’s too dark the person may become distressed as seeing things becomes harder, but if it’s too bright it may cause overstimulation.

Contact our circadian specialists to learn more about using light to alleviate sundowning behaviours.

Blue Light has a Dark Side

A great article from Harvard Medical School about the importance of eliminating blue light at night. Dr Steven Lockley, cited in the article is a sleep advisor to PhotonStar following grant funding from the Department of Energy and Climate Change (as it was at the time of award). One of the core principles of our circadian lighting solution is eliminating blue light at night.