Reading between the lines: – and worms seeing in full colour

Recovered from Daylight Savings yet?

You can thank the International Meridian Conference held in Washington 140 years ago in 1884 for the introduction of time zones and this government-sponsored global experiment in social jet lag that sparks a passionate debate every year.

In this fascinating paper, Professor Timo Partonen reviews the evidence for and against Standard and Daylight Savings Time and switching between them, pointing to the acute and chronic effects of misalignment between three competing paradigms – Daylight Saving Time and Artificial Time Zones – A Battle Between Biological and Social Times.

1. Sun clock: local progression of the sun: noon when the sun is highest in the sky and midnight, exactly halfway between dusk and dawn.
2. Social clock: the local clock displayed on computers and wristwatches set by policy, a shared social construct.
3. Body clock: your internal time that drives a complex cascade of physiological functions from activating genetic expression to your ability to think straight and smile. Your body clock is largely set by exposure to contrasting levels of light and darkness. The way that light-dark contrast is expressed in hormones and behaviour (for example, how soon you feel tired after it gets dark) is known as your chronotype: a lark is ready for bed long before a night owl.

The sudden shift to Daylight Savings creates a clear disconnect between these three forms of time-keeping – the evenings are ‘lighter’.

But you may be less aware of the substantial drift between sun clock and the social clock within a single time zone and the subtle yet powerful impact on your mental and physical health: for someone living in the North West of Spain, 12 noon on the clock is just 10:30am in sun time.  Someone who lives in the western edge of a time zone, with later sunrise and sunset times is at higher risk of depression, gets less sleep, doesn’t do as well at school and even earns less compared to those living in the East according to a large study of adults in India, China and Indonesia – Poor Sleep: Sunset Time and Human Capital Production.  

This lack of sleep is compounded by extended exposure to electric light and shorter (and incomplete) periods of darkness. This leads to weaker body clock signalling and a drift in the natural distribution of chronotypes towards extreme night owls, further compromising sleep.

We know so much more than the delegates at that Washington conference 140 years ago. Partonen makes a compelling case that, not only should we scrap the Daylight Savings Time convention.

We should redraw the social time zones to rebuild the lost link between the sun and our bodies.

For those of us who are passionate about circadian lighting, this realignment cannot come too soon.

Between the lines – how to read a scientific paper

How do you know if a scientific ‘fact’ is true?

The evidence about the impact of light on health is moving so fast it’s hard to keep up!

So I find going back  as much as I can  is a really great starting point.

But if you, like me. didn’t learn science at school, looking at those papers  can be really daunting.

So here are some tips which might help you to discover the joys of reading a scientific paper so you can be sure of your facts too!

When you search for a topic, thousands of references will come up… How do you know which ones to look for? I use Google Scholar because it gives me lots of great information.

The first is to look at the date. I try and find the most recent papers first because the science is moving so fast. Older papers often don’t reflect  new ways of thinking.

Next look at the number of citations. Often a high number of citations suggest that other scientists find that paper really important too. 

So let’s take a look at this classic paper cited by lots of people and in a good quality journal.

Brown TM Melanopic illuminance defines the magnitude of human circadian light responses under a wide range of conditions – Melanopic illuminance defines the magnitude of human circadian light responses under a wide range of conditions.

We know that Tim Brown is an amazing scientist in the field, so everything he has to say is likely to be useful. 

The abstract is like an executive summary. It will give you the context, the method and the main results

The introduction is a great place to gather information about the context and the overall perspective of the scientist.

Materials and methods: here it’s worth taking a very critical view. How big is the sample? How long was it for? What are the other things that we know make a difference in this setting?

Results and discussion. For those of us who aren’t particularly confident about maths, this can be a really tricky section to read.

But a good paper will give you lots of diagrams so you can set the maths  in context of a graphic.

Conclusions. Worth spending time here. They will explain what they found, why it’s important, other limitations and concerns they might have, and opportunities for further study.

Acknowledgements and conflict of interest. Sometimes you will see  that the study or the authors have been sponsored  or had a commercial relationship. 

That doesn’t necessarily mean that study isn’t valid or independent.

It’s simply worth adding to your understanding of the perspective of the paper itself.

Something else worth looking at is the references. That’s the literature that they reference to create the paper themselves. I always learn so much not only about the quality of the paper but I discover a whole new world of information to explore

I hope this inspires you to go back to look at those original sources too!

Big data and your body clock

Looking forward to this session with Dr Angus C Burns next Monday – Current Topics in Sleep & Circadian Health, and hearing about his innovative research, most recently leveraging over 280,000 records in the UK Biobank to identify connections and trends at scale.

Here are two recent examples of his work with Biobank data: uncovering the link between light sensitivity and chronotype – Genome-wide gene by environment study of time spent in daylight and chronotype identifies emerging genetic architecture underlying light sensitivity, the other between circadian disruption and mortality – Light at night and modeled circadian disruption predict higher risk of mortality: A prospective study in >88,000 participants.

Worms don’t like blue LEDs either!

I’m a great fan of worms, especially since I got my allotment – I know not everyone may agree.

But did you know that even though they don’t have eyes or even a brain to process signals, they can sense light and darkness – and tiny round worms can even sense bright blue light. Post-doc student Dipon Ghosh noticed that the worms in his lab seemed to lose interest in food when illuminated by a nearby white LED. He changed the bulbs to discover that it was the blue wavelengths rather than the brightness that triggered the response – a colour associated with a toxin excreted by a microbe to put off predators. Another reason to celebrate the humble worm! – Eyeless roundworms sense color.