Sleep Disorders Glossary L

Sleep Disorders Glossary - L


Lark is a person who prefers go to bed early in the evening and rise early in the morning. Lark is also called a morning person or morning lark This tendency becomes more common in the elderly.

Laser-assisted Uvulopalatoplasty [LAUP]

Laser-assisted uvulopalatoplasty (LAUP) is a surgical treatment for habitual loud snoring or obstructive sleep apnea. In this surgery, it involves removal of the back edge of the palate, the uvula, and if present, the tonsils.

It requires multiple procedures where the laser reduces tissue of the palate and the area heals by scarring. It is an outpatient procedure performed under local anesthesia.

Latency Period

Latency period is an interval. Sleep latency is is the length of time that it takes to go from full wakefulness to falling asleep. During daytime, a sleep latency of 15-25 minutes is considered normal.

A shorter sleep-latency is likely a sign that the person suffers from sleep-deprivation. A sleep-latency of less than five minutes would indicate either very unhealthy daytime sleepiness or some sort of sleep-disorder.


L-Dopa An amino acid that is the metabolic precursor of dopamine, is converted in the brain to dopamine, and used in synthetic form to treat Parkinson's disease. Also called levodopa.

It is often helpful in managing Restless Legs Syndrome and Periodic Limb Movement Disorder. Examples include L-Dopa with Sinemet (carbidopa), Permax (pergolide), and Parlodel (bromocriptine).

Leg Movement

Leg movements are recorded in diagnostic sleep studies to test for Periodic Limb Movement Disorder.

Letter of Medical Necessity (LMN)

Letter of Medical Necessity (LMN) is a special document that is a certification by a physician to a pharmacist or other therapist for a treatment to be provided to their patient .


Leucomaines is the name for the poisonous substances that supposedly accumulated during the day and passed from the blood to the brain. It is an animal base or alkaloid, appearing in the tissue during life.

Light box

Light box is a commercially obtainable, electrically powered device that provides artificial light. It is a treatment option for patients with Seasonal Affective Disorder, Advanced Phase Sleep Disorder, or Delayed Phase Sleep Disorder.

Light-Dark Cycle

Light-Dark Cycle is the periodic pattern of light (artificial or natural) alternating with darkness.

Light Sleep

Light sleep is the common term used to describe non-REM sleep stage 1, and sometimes, stage 2. Eyes move very slowly and muscle activity slows. People awakened from stage 1 sleep often remember fragmented visual images.

People in light sleep drift in and out of sleep and can be awakened easily. Many also experience sudden muscle contractions called hypnic myoclonia, often preceded by a sensation of starting to fall.

Light Therapy

Light therapy form of therapy where the person is exposed to bright light at the appropriate time of day to effect the timing, duration and quality of sleep. It is a treatment for various disorders including seasonal affective disorder, depression, hypersomnia, and delayed phase sleep disorder.

Limit-Setting Sleep Disorder

Limit-Setting Sleep Disorder is primarily a child disorder that is characterized by the inadequate enforcement of bedtimes by a caretaker, with resultant stalling or refusal to go to bed at an appropriate time .

Linear Sleepiness Rating Scale

Linear Sleepiness Rating Scale is a measure of subjective sleepiness. The scale consists of a horizontal line, 100 mm in length on which the left extreme is labeled "Very Wide Awake" and the right extreme is labeled "Very Sleepy."


Lingualplasty is a surgical treatment of sleep apnea or snoring. Lingualplasty involves a resection of the tongue is done with additional removal of side wedges in order to reduce the back of the tongue and open the lower airway.

Lingual Tonsils

Lingual tonsils - tonsil-like tissue on the back part of the tongue.


Lux - a measure of light intensity; the unit used by light box manufacturers to describe light output.

Luteinizing hormone

Luteinizing hormone - A hormone produced by the anterior lobe of the pituitary gland that stimulates ovulation and the development of the corpus luteum in the female and the production of testosterone by the interstitial cells of the testis in the male.


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