Advanced Sleep Phase Syndrome (ASPS) – a condition where patients feel very sleepy and go to bed early in the evening, and wake up very early in the morning.  Extreme larks.

Blue-blockers – spectacles whose lenses filter out 100% of blue light and are thus used in darkness therapy to allow the body to produce melatonin.  They may be yellow, orange, amber red or brown in colour.

Bright light therapy – the practice of using very bright light, usually in the form of therapeutic lightboxes, to treat various conditions such as SAD and sleep disorders.

Chronotherapy – the practice of going to bed three hours later every night in order to shift the circadian clock.  High failure rate; not recommended.

Circadian rhythm – the “body clock”, the cyclical 24-hour period of human biological activity.

Cortisol – a hormone produced in the adrenal gland.  Best known as the “stress hormone”, it should rise in the morning and be low at night.  Research has shown morning cortisol levels to be low in women with ME/CFIDS.

Darkness therapy – also called dark therapy.  The practice of filtering out blue light (or in some versions, all light) in the evenings in order to stimulate melatonin production and aid sleep.  Most studies look at its effects on bipolar disorder.

Dawn simulation – the practice of setting a light or lights to come on gradually in the morning, simulating a sunrise, to wake the body naturally.  Mostly used as an alternative alarm clock, but also valuable in SAD and sleep disorders.

Delayed Sleep Phase Syndrome (DSPS) – a condition where patients are wakeful in the evening, cannot get to sleep until several hours past midnight, and cannot wake up until late in the day.  Not the same as insomnia, although it has much in common with it.  Extreme night owls.

Dusk simulation – the practice of setting a light to go off gradually in the evening, simulating a sunset.  Most dawn simulators have a dusk simulation function.

Fluorescent – the most common type of energy-saving bulb, used routinely in commercial lighting applications and becoming increasingly popular for domestic use, although many people find the light to be cold and unpleasant.  Strip lights are fluorescent, as are the spiral bulbs for domestic use.  They claim to offer an energy saving of 70% compared to incandescents, although many people find it is not quite that much.  Typical wattages are 7W, 11W, 14W and 20W.  Most of these bulbs cannot be dimmed, but while a few new ones are dimmable, they are not suitable for use with dawn simulators.

Halogen incandescent – also known as low-energy halogen, energy-saving halogen or dimmable halogen.  A new type of halogen bulb which is the same shape as an incandescent bulb and will fit into a standard (incandescent) lamp fitting, but contains a halogen capsule inside.  They offer an energy saving of at least 30% compared to incandescents, and the light is generally agreed to be very pleasant to the eye, being a warm white that is a little whiter than incandescents.  Typical wattages are 28W, 42W and 70W.  These bulbs can be dimmed and are ideal for dawn simulators.  Not to be confused with traditional halogen bulbs, which do not fit incandescent fittings or look like incandescent bulbs, and which cannot be dimmed.  Example may be seen here.

Incandescent bulb – the most common type of domestic light bulb, often pear-shaped, and appearing in wattages such as 40W, 60W and 100W.  Many countries are now phasing these out as they consume a great deal of energy, although many people find that the somewhat yellowish light they produce is more pleasant than the alternatives.  These bulbs can be dimmed and are suitable for dawn simulators, although they are prone to buzzing when used in that way.  Also known as Tungsten bulbs.

Insomnia – persistent difficulty falling and/or staying asleep.

Lark – a person who is naturally wired to wake up and go to sleep relatively early.  When this is taken to an extreme level, it becomes Advanced Sleep Phase Syndrome. Early birds, morning people.

LED – light emitting diode, a type of light source.  LEDs are used in a variety of applications, from cars to remote controls to bright light boxes, but as yet are not really used in domestic lighting.  LED light bulbs are rare and unsuitable for use in plug-in dawn simulators.

Lightbox – also known as light box or bright light box.  A unit which produces very bright light, most often 10,000 lux, using either fluorescent tubes or LEDs, in order to produce an effect similar to that of being under strong sunlight.  Primarily used to treat SAD, it is also very useful for sleep disorders and non-seasonal depression as it stimulates serotonin.

Light therapy – can refer to any form of therapy that utilises light, but most often refers to bright light therapy and may sometimes include dawn simulation.

Lux – unit for measuring illuminance (light levels).

Melatonin – a hormone with many complex functions, of which the best-known is regulating sleep.  It is only secreted in darkness.

ME/CFS/CFIDS – A complex neuro-immune disorder which ranges from mild to extremely disabling.  ME (Myalgic Encephalopathy, sometimes Myalgic Encephalomyeltis) is the most common name used by patients in the UK.  CFS (Chronic Fatigue Syndrome) is commonly used by doctors, and CFIDS (Chronic Fatigue and Immune Dysfunction Syndrome) is the most common American term.  For more information, see the Links page.

Night owl – person who is naturally wired to go to bed and get up late.  When this is taken to an extreme level, it becomes Delayed Sleep Phase Syndrome.  Evening people, nocturnal.

Non-24 Sleep Wake Disorder – a sleep disorder where the circadian rhythm (body clock) runs on a day other than 24 hours, most commonly 25 or 26.

Seasonal Affective Disorder (SAD) – a mood disorder in which patients become depressed during the winter.  The primary cause is considered to be low serotonin levels due to lower levels of daylight.  Some people experience mood disorders during the summer, which may be called Reverse SAD.

Serotonin – a neurotransmitter which contributes to a good mood and feelings of wellbeing.  Stimulated by light, so that inadequate light levels lower serotonin and may trigger depression.

Siesta – a nap taken in the early afternoon, usually after the midday meal.  Common in warmer countries.

Sleep apnoea – a sleep disorder characterised by pauses in breathing during sleep.

Sleep cycle – the 90-110 minutes it takes to go through the four (some say five) stages of sleep.  There will be several complete cycles of sleep during a night’s rest.  Most people naturally sleep in multiples of 90 minutes.

Sleep debt – the cumulative effect of not getting enough sleep; when you end up sleeping in a great deal on weekends due to insufficient sleep during the week.  A sign that you either need to sleep more, or that you need to improve the quality of your sleep.

Sleep gate – the time during the day when melatonin peaks and you naturally feel sleepy.  Sleep gates tend to occur at 3 hour intervals.  Sometimes called the sleep wave.

Sleep hygiene – the practice of controlling behavioural and environmental factors in an attempt to ensure more restful, effective sleep.

Tinnitus – the medical term for any noise heard in one ear, both ears, or the head, which does not come from outside the head.

Virtual darkness – this occurs when there is no blue light visible, i.e. when using blue-blocking spectacles or light bulbs which do not emit any blue light (yellow, orange or red bulbs).  Since it is only blue light which affects the circadian clock, this is registered by the body as darkness.

Zeitgeber – any agent or cue which synchronises the human body to the earth’s 24 hour clock, of which the most important is light.

One Comment on “Glossary”

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