Medical Center

We live on a rotating planet, submitted to alternating cycles of day and night and the seasons. These geophysical patterns of illuminance have left their record in the genes of organisms evolving under pressure of survival. Darwinian necessity underlies the remarkable similarity in „clock genes“ from bacteria to humans. A biological clock ticking near the frequency of 24 hours provides an internal template for every living cell, so that it be ready to respond appropriately to external conditions. To find food, to rest, to avoid predation, to reproduce: these basic functions need to be optimised within a temporal framework: a circadian rhythm. The biological clock is also a clock for all seasons – it can measure changing daylength. The molecule that transduces this daylength signal is the pineal hormone melatonin. Melatonin is synthesised only during the night, and thus acts as a hormonal signal of darkness – longer in winter, shorter in summer. Light immediately suppresses melatonin synthesis.

Humans are responsive to these day-night cues, though they usually never see them. Exposure to natural light is markedly reduced by living and working mostly indoors under artificial lighting. In this respect, human biology is rather like that of the European squirrel, which burrows into its underground nest in the Hungarian puszta in the late afternoon and doesn’t emerge till mid-morning: the squirrel never sees dawn or dusk. Yet its biological clock still somehow manages to use whatever daytime outdoor light it sees to synchronise activity – and reproduction and hibernation – to the changing daylength of the seasons. Humans are not quite so ecological as squirrels, in that they receive even less light during the day, and more erratically, day by day: sometimes more, sometimes less, sometimes early, sometimes late. Most people, like squirrels, somehow adequately synchronise their sleep-wake cycles to the 24-hour day. But some do not.

Both the timing and amount of light received are important for the melatonin signal, and for sleep, vigilance and mood. This is particularly noticeable in a group of depressive patients whose symptoms appear in autumn and winter, and spontaneously improve in spring and summer. Just like squirrels preparing for hibernation, they eat more, gain weight, and sleep more in autumn. The surprising and important finding is that 30-60 minutes of bright light a day (whether from an artificial lamp or outdoors) is sufficient to rapidly improve clinical symptoms. In temperate latitudes, about 2% of the adult population suffer from winter depression, and a further 10% from a milder form that has been given the name “winter blues”. Further north, the prevalence is higher. Seasonal depression reminds us that the importance of light for human well-being should not be underestimated. Light therapy is also a helpful non-pharmacological treatment for certain sleep-wake cycle disturbances, such as in the elderly and Alzheimer’s patients.

Descartes described the pineal gland as “the seat of the soul”. Yet the role of melatonin in humans is still unclear. Melatonin is sold freely in drugstores in the USA as a “vitamin supplement”, even though it is not a vitamin, the illnesses it should cure are not sufficiently researched, the dose required not established, the side-effects with long-term use not known. Thus, it should be used with caution as a pill for insomnia or promoting long life. Melatonin administered during the day (when it is not naturally produced) does induce sleepiness and impair performance. It has little effect on sleep regulation as such (compared with benzodiazepine sleeping pills). Melatonin also synchronises circadian rhythms, as does light, in that it can shift the timing of the sleep-wake cycle depending on the time of administration. This is the rationale for its use to prevent the symptoms of jet-lag and help rapid adjustment to a new time zone. One established clinical application of melatonin is to help synchronise the sleep-wake cycle of blind persons, who often have circadian sleep disturbances and obviously, cannot be treated with light therapy.

The “melatonin room” brings LIGHT and DARK into a visible space – creatively interpreting these scientific concepts in an installation physically experienced. Light and wakefulness, melatonin and sleepiness, the yin and yang of the biological clock that times our being on this planet.

Catalogue MELATONIN ROOM
Décosterd & Rahm, architects
Editions Jean-Michel Place, Paris

BODYCLOCK
Anna Wirz-Justice Ph.D.
Centre for Chronobiology
Psychiatric University Clinic
CH-4025 Basel, Switzerland