Tunable, dynamic or circadian – and seagulls never forget a face!

Tunable, dynamic or circadian…

What’s the difference (and do they work?)

All three have two or more LED chips mounted in the same fitting. The user or automated control can adjust the power going through each chip, changing how the light looks.

• Tunable: Adjusts colour temperature and brightness, manually or with pre-set ‘scenes’
• Dynamic: Uses automated systems to adjust lighting conditions based on schedules, sensors, or environmental inputs.
• Circadian: A subset of dynamic lighting, uses automated schedules to mimic the day-night cycle to deliver the current recommended light levels: >250 Melanopic Lux (MelEDI) for at least four hours during the day, <10 MelEDI in the evening and <1 MelEDI at night – Recommendations for daytime, evening, and nighttime indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults.

Do they work?

This review by Kompier et al. found that dynamic lighting is good for human function overall, with most studies focusing on sleep. But they point out that inconsistent methods and measures make it hard to give a simple ‘yes/no’ response – A systematic literature review on the rationale for and effects of dynamic light scenarios.

But here are three recent papers that suggest dynamic lighting might be worth a look:

Simulated space flight – The effect of a dynamic lighting schedule on neurobehavioral performance during a 45-day simulated space mission.

This 45-day simulated space mission compared a dynamic with a static lighting schedule. It builds on an earlier study that demonstrated improved circadian alignment and performance under dynamic lighting schedules (high melanopic lux during the day, low in the evening, and darkness at night) – Effects of dynamic lighting on circadian phase, self-reported sleep and performance during a 45-day space analog mission with chronic variable sleep deficiency. This time, the team looked at reaction time and attentional lapses and found that both were better with dynamic light, even towards the end of the study when participants were suffering from a lack of sleep.

Shift work – The effects of dynamic daylight-like light on the rhythm, cognition, and mood of irregular shift workers in closed environment.

You don’t have to live on the space station to live in another time zone. Around 14% of working adults in the UK are classified as shift workers, often in critical or dangerous conditions – nurses, truck drivers, oil rig operators and air traffic controllers. Disrupted sleep not only impairs critical reaction time, decision-making and accuracy, but it also plays havoc with a cascade of physiological and behavioural patterns. After 38 days under dynamic lighting, participants’ peak melatonin levels increased while their physiological and behavioural rhythms remained stable. Another study in a simulated underground lab also found that dynamic lighting improved the quality and quantity of sleep – Active interventions of dynamic lighting on human circadian rhythm and sleep quality in confined spaces.

Office

Dynamic lighting also seems to offer some benefits even in spaces only occupied during the day – although the effects are less clear-cut, perhaps due to the lack of control over participants’ light exposure outside working hours or at home. This is one of several studies that suggest that dynamic lighting improves mood, sleep and sustained attention, although inconsistencies suggest that the optimal cycle still needs to be refined – Temporal tuning of illuminance and spectrum: Effect of a full-day dynamic lighting pattern on well-being, performance and sleep in simulated office environment.

This paper includes a valuable reminder that artificial light is not enough alone. Dynamic lighting really comes into its own when combination with daylight, dynamic shading and lighting controls, boosting mood, performance, and well-being while saving energy – Optimized office lighting advances melatonin phase and peripheral heat loss prior bedtime.

Dynamic lighting on a shoestring 

You might be lucky enough to go into an office kitted out with the latest tech. But what can you do at home (and on a budget) to achieve a similar clock-setting, mood-boosting effect?

Three simple things will do the same basic job: 

1. Access to a view – the best clock-setting trick of all – Access to Daylight at Home Improves Circadian Alignment, Sleep, and Mental Health in Healthy Adults: A Crossover Study.
2. Bright, cool light from above during the day to create a spacious, ‘sky dome’ effect – Light Distribution and Perceived Spaciousness: Light Patterns in Scale Models.
3. Switch off computer and lights to signal the end of the working day – Working from Home with Flexible and Permeable Boundaries.

One for the diary 

Monday’s guest on the brilliant series Current Topics in Sleep & Circadian Health is the legendary Professor Lauren Hartstein, one of the pioneers of circadian research in children and adolescence. I’m hoping she’ll share her perspective on extreme sensitivity to light before bedtime – High Sensitivity of Melatonin Suppression Response to Evening Light in Preschool-Aged Children, the growing use of melatonin by pre-school children – Optimal sleep and circadian habits in infants and children, and how lunar phase affects the body clock from the first years of life – Evidence of circalunar rhythmicity in young children’s evening melatonin levels.

See you there!

Seriously smart seagulls  

You might think seagulls are a pest

But really, they deserve some respect!

They can spot your ice cream from nearly 2 kilometres away – Avian vision.

They’ll remember a face, especially if you’ve fed them before – Searching for Face-Category Representation in the Avian Visual Forebrain.

And they’ll remember your food preferences: If they’ve seen you eat from a red package, they’ll choose a red package too – Inter-species stimulus enhancement: herring gulls (Larus argentatus) mimic human food choice during foraging.

Maybe it’s time to take those seagulls seriously!