Do iPads and electric lights disturb sleep?

"Terrible night's sleep? Blame your mobile phone" is the advice on the Mail Online website, as "exposure to artificial light 'fools' the brain into staying awake."

This – and similar headlines in the Daily Express, The Guardian and Metro newspapers – is based on a recent opinion piece in the journal Nature, which has published a dedicated supplement on the science of sleep.

The opinion piece suggests that the invention of electric light has altered our sleep patterns over the last century. In particular, the widespread use of LED lights, which we rely on to view smartphones, tablets, televisions and laptops screens, is disrupting our sleep.

This, the author suggests, could have potentially serious health consequences, as poorly controlled insomnia can cause both physical and mental health problems.

As an opinion piece, this should not be taken as evidence that light exposure hampers our ability to sleep. However, it does suggest several ways the two may be linked. The piece offers the theory that one causes the other, but these associations have not been directly tested. But given that the author is a specialist in sleep medicine, his opinion cannot simply be dismissed out of hand.

Who wrote the opinion piece?

The editorial was written by Charles Czeisler, a professor of sleep medicine at Harvard Medical School and chief of the division of sleep medicine at Brigham and Women's Hospital in Boston, US.

Over the past 35 years Dr Czeisler has published widely on sleep, the impact of light on sleep, and the effect of restricted sleep on human behaviour and performance.

What arguments are made?

Dr Czeisler suggests that since the invention of electric light, there has been a fundamental shift in our sleep patterns. He argues that light has enabled us to evolve into a "24/7 society", and that many of the features of this transformation – early starting times at work and school, long commutes, high doses of caffeine – lead to us getting insufficient amounts of sleep.

Dr Czeisler's arguments for the link between the increasing use of electric light and disrupted sleep have highlighted several issues.

The biological effect of artificial light

Dr Czeisler argues that exposure to artificial light during the evening and at night could block the effects of brain cells that help promote feelings of sleepiness, as well the "sleep hormone" melatonin.

At the same time, artificial light could also stimulate brain cells associated with alertness.

The combination of these effects could result in many of us feeling much less sleepy in the evening than we would normally.

Time-trends in light use, cost and sleep

Dr Czeisler reports that the cost of generating light dropped dramatically over the last 50 years, which was associated with an increase in the use of artificial light.

At the same time that the use of artificial light increased, reported levels of sleep deficiency also went up. A recent study looking at data in England from 1993 to 2007 found a continual increase in people seeking treatment for sleep disorders.

However, it is important to note that, as with any observational time-trend data, this argument only outlines associations between light consumption and sleep deficiency, and should not be interpreted as there being a causal relationship based on this editorial alone.

Increased use of LEDs

Dr Czeisler suggests that the recent move from traditional incandescent light bulbs to more energy efficient solid-state light-emitting diodes (LEDs) could further disrupt our sleep.

LEDs are commonly used in TVs, computer screens and handheld electronic devices such as tablets. These LEDs are typically rich in shortwave length (blue and blue-green) light, which the cells in our retina are more sensitive to.

He offers the theory that time in front of these blue light-rich screens at night will be more disruptive to our sleep than incandescent lighting.

Interestingly, one of the final discussion points in the editorial is about our ability to control the wavelengths emitted by LEDs. Dr Czeisler suggests that any adverse effect of exposure to these lights at night could be mitigated by replacing blue heavy light with red or orange heavy light in the evenings.

This editorial offers interesting discussion points surrounding the relationship between light – especially evening or nighttime exposure to light – and difficulty sleeping.

What evidence is cited?

Dr Czeisler's article makes reference to several publications, mainly centred around trends in the average number of hours adults and children sleep each night, and the prevalence of the adverse effects of sleep deprivation. As an opinion piece, the overall discussion points are narrative in nature and are not based on any individual piece of research or evidence.

This specific article on its own cannot provide evidence of a direct link between light exposure and sleep deprivation. However, it is not intended to do so. It offers a broad introduction to a series of articles on the topic, and suggests we consider the ways in which technological changes may impact our ability to get a good night's sleep.

Conclusion

It is certainly possible to reduce your exposure to artificial lights. For example, you could dump your smartphone, give away your iPad, banish television from your home, and refuse to work in any job that involves using a computer. But adopting this kind of luddite lifestyle is probably not to most people's tastes.

One proven method of improving your sleep is what is known as "sleep hygiene". This is where you control both physical and environmental factors in order to promote sleep.

Examples of good sleep hygiene include:

not drinking tea and coffee four hours before bedtime
avoiding drinking alcohol or smoking before bed
using thick blinds or curtains, or wearing an eye mask if the early morning sunlight or bright streetlamps affect your sleep
wearing ear plugs if noise is a problem