Early morning birdsong

Lighthouse on the cliff tops of Cromer, Norfolk.                                       Photo: Clive Simpson

Are you sleeping well on these long end of winter nights? If not then part of the answer may be in how dark your bedroom is.

As we travel through winter, with its emerging hint of longer days and promise of spring, it is appropriate to revisit the theme of some previous blog articles about night, darkness and the effect of artificial light on our modern lives.

The other morning I awoke midway through the night at around 3 am to hear birdsong outside. Normally a welcoming sound but at that hour, and with dawn still some four hours away, a little disconcerting. 

Birds singing during the ‘night’ is no longer such an infrequent occurrence. It is a somewhat troubling development and perhaps an indicator of wider factors at play. 

The birds it seems are often duped by our brightly lit streets, on-off ‘security’ lights and other forms of night-time illumination and general light pollution, into thinking daylight has arrived early.

And here’s the thing. All of us, birds included, are hard-wired to sleep in darkness, not in bedrooms full of light, computer monitors, digital alarm clocks or TV stand-by lights.

Chronic exposure to light at night is bad and, to understand why, we need to look into the past. Prior to the end of the Stone Age, humans were largely exposed to just two different kinds of natural light.

During the day we had the sun, while at night we had the moon and the stars, and perhaps the light from campfires. The binary day/night pattern was unrelenting, and our biological programming followed suit.

So why can't you get a good night's sleep? The problem is that many of us probably don't realise what makes us fall asleep in the first place. 

Compared to our ancestors our bodies’ circadian rhythms now also have artificial lighting at night (LAN) to contend with. Indoor lighting may be considerably less powerful than sunlight but it is certainly many orders of magnitude greater than star and moonlight. 

Melatonin suppression is key to understanding much of why LAN is bad for us, particularly in the winter months of the northern hemisphere.

This workhorse biochemical is produced at night when it is dark by the brain's pineal gland  to regulate our sleep-wake cycle. It lowers blood pressure, glucose levels and body temperature — key physiological responses responsible for restful sleep. 

The part of our brain that controls the body’s biological clock is known as the Suprachiasmatic Nucleus (SCN), a group of cells in the hypothalamus which respond to light and dark signals. 

The optic nerves in our eyes sense light and transmit signals to the SCN telling the brain when it is time to wake up, which also kickstarts other processes, like raising body temperature and producing hormones such as cortisol. 

Normally our cortisol levels are relatively low at night - allowing us to sleep - and higher during the day, allowing for the stabilisation of energy levels and the modulation of immune function. 

But LAN unnaturally elevates cortisol levels at night, which can then disrupt sleep and introduce a host of problems relating things like body-fat levels and insulin resistance. It also contributes to sleep debt and can disrupt the regulation of appetite.

If, on the other hand, our rooms are properly dark at night there is no optic signal to the SCN, so our bodies pump out the much needed melatonin. 

Light exposure during the previous day can also affect melatonin levels - studies have shown that exposure to bright room light before bedtime shortens melatonin duration by about 90 minutes compared to dim light exposure. In addition, exposure to room light during usual hours of sleep suppresses melatonin levels by more than 50 percent. 

So, even before you hit the hay, the light in your bedroom may be causing you problems. With the introduction of tablets (not the sleeping kind), smartphones, and energy-efficient LED light bulbs, it's an issue that's only getting worse. 

And just to add insult to injury, many modern LED (light-emitting diode) devices emit blue light which is especially good at suppressing melatonin. This is because melanopsin — a photo-pigment found in specialised cells of the retina involved in the regulation of circadian rhythms — is most sensitive to blue light. 

Regrettably, all this hormone and biochemical disruption is creating downstream effects — and studies are now showing correlations with weight gain problems, the incidence of cancer, depression and adverse effects on the immune system.

Essentially we need to keep our bedrooms as dark as possible and avoid blue light before sleep. 

You might want to think about this next time you leave even the dimmest lights on in your bedroom overnight — including your clock radio and the light that bleeds in through the curtains from nearby street lights. 

Why not try removing electronic equipment from the bedroom and using dimmer lights before before you turn in, as well as refraining from viewing TV, smartphones and computer screens for up to an hour before bed?

And if your bedroom is affected by artificial light from outside (and blackout curtains don’t do the trick) speak to your local council about street light shielding, and maybe your neighbour about realigning any problematic external floodlights.

Oh, and while we’re at it, switch off that bl**dy lighthouse! Sleep well, zzz zzz.

The Lighthouse Keeper is written by Clive Simpson - for more information or to get in touch click here