These days, anyone who regularly uses the internet or reads the news is faced with a barrage of unsolicited advice about how to get more and better quality sleep, sometimes in a way that suggests that better sleep is the key to a better life. With headlines such as “Five things that stop a good night’s sleep” and “Ten reasons why you’re not getting a good night’s sleep”, it’s hard not to feel like you’re doing it all wrong, even if you don’t feel as though sleep (or lack thereof) is a considerable problem in your daily life. Is reading on your smartphone or tablet before bed really killing you? Or is it a harmless habit as long as you dim the lights and hold it a foot away from your face? Will wearing socks to bed change your life by helping you fall asleep a few minutes faster, or will it just give you uncomfortably warm feet? How are we supposed to know what to believe when it comes to our coveted beauty sleep?
Although often contradictory, the one thing that most advice on sleep has in common is that it targets the neurobiological mechanisms that underlie the feeling of sleepiness and the onset of sleep. When light strikes the retina of the eye, special photoreceptors called melanopsin cells convert the light energy into a neural impulse, which travels to a region of the brain called the suprachiasmatic nucleus (SCN). This tiny structure is often referred to as the “body clock” as it is responsible for a number of complex interactions controlling our sleep-wake cycles such as the regulation of body temperature and the secretion of hormones. One of these mechanisms is the synthesis and secretion of melatonin, the hormone that makes us feel sleepy. During hours of daylight, the SCN inhibits melatonin secretion by the pineal gland, keeping us awake and alert during the day. Accordingly, with decreasing levels of light in the evening and at night, melatonin production is increased, making us feel drowsy and encouraging our bodies to go to sleep. This melatonin regulation circuit is the main target of a booming industry of so-called natural sleep aids.
Direct ingestion of melatonin has been shown to be remarkably effective in preventing or reducing jet-lag by helping to re-align the body’s rhythms with the day-night cycle of the travel destination. In the United States and Canada, melatonin tablets are sold over the counter as dietary supplements of varying strengths, right next to the multivitamins and omega 3 oils (this is in contrast to most EU countries, where a prescription is required to purchase melatonin). There even exists a melatonin spray, optimistically named Sprayable Sleep. Inspired by the recent discovery of cutaneous melatonin receptors, the spray is meant to be applied to the skin shortly before sleep, and claims to help you “fall asleep naturally and wake up refreshed”. Other types of natural sleep aids target the influence of light on the melatonin circuit by minimizing exposure to certain wavelengths before bedtime. The melanopsin cells in the retina are most sensitive to blue light, the same wavelengths emitted by the back-lit screens of laptops, tablets, and smartphones, as well as some types of fluorescent or energy-efficient light bulbs. Blue light is interpreted by the SCN as daylight, which suppresses melatonin production and keeps you awake. Unsurprisingly, this finding has triggered a wealth of discussion on how blue light from electronics disturbs sleep, which could have serious health implications, especially for teenagers (For a related and comprehensive discussion of whether or not screens are harmful for young people, tune in to the latest episode of All in the Mind on BBC Radio 4 by Hubbub core group member Claudia Hammond). By filtering out the ‘bad’ wavelengths of light, a number of commercial products such as amber-lensed blue light filtering goggles and UV/blue-safe light bulbs aim to stimulate melatonin production without the need for ingestible supplements. The more fashion conscious consumer might instead opt for an app that adjusts the screen colors on your backlit devices according to the time of day and your regular sleep/wake schedule, or the low-tech alternative of a stick-on blue-blocking screen filter.
As a scientist, I know that the melatonin circuit is the biological driving force behind our natural sleep-wake cycles. However, as someone who is prone to dozing off during movies played from a blue-light emitting computer screen, and at other times unable to fall asleep in complete darkness, I can’t help but feel a certain degree of scepticism about the supposed prominence of their role in regulating my own body clock. It is important to remember that melatonin does not actually induce sleep, but rather signals to the brain and body that it’s time to prepare for sleep. For this reason, melatonin will only be able to do its job within a context that encourages and invites restfulness and sleep, and the efficacy of natural sleep aids that target melatonin production is likely to be influenced by numerous environmental and psychological factors. As anyone who has experienced insomnia (whether short- or long-term) would likely agree, there’s a lot more to what’s keeping you awake at night than hormonal interactions.
In the context of the hubbub project, I’m interested in trying to disentangle the subjective experience of sleepiness (as well as sleeplessness), from the objective mechanisms that underlie them. To what extent is the quality of our sleep driven by biology, and to what extent is it driven by thought? What kinds of thoughts are keeping us awake? Are we most often ruminating over deep existential questions like the ones on this list of worries that keep people awake at night, or is our sleep just as easily disrupted by simpler distractions like the sound of a dripping tap or the length of tomorrow’s to-do list? Ironically, something that quite often keeps me awake at night are thoughts about falling asleep, and sometimes, the more important it is for me to get a good night’s sleep, the harder it is to do so. By considering these questions from an interdisciplinary perspective and situating reductionistic approaches that pervade public understanding of such topics in appropriate contexts, we might start to shed some light on what, if anything, we should be doing to improve our rest and sleep.