Search the Health Library
Get the facts on diseases, conditions, tests and procedures.
I Want To...
Find a Doctor
I Want To...
Find Research Faculty
Enter the last name, specialty or keyword for your search below.
Conditions & Disorders
- Chronic Insufficient Sleep
- Circadian Ryhthm Disorders (CRD)
- Obstructive Sleep Apnea
- Restless Legs Syndrome (RLS)
The most common explanation for complaints of sleepiness in our society is inadequate sleep. Due to the stress and rigors of society, most Americans often get less than 7 hours of sleep per night. Based on the current sleep deprivation research findings, most individuals require 7.5 to 8.5 hours of sleep nightly in order to function at their best, emotionally, cognitively, and physically. Sleep deprivation can also magnify the severity of other sleep disorders including sleep apnea and restless legs syndrome.
The brain has an internal clock that regulates several biorhythms including the timing of an individual’s sleep-wake cycle. In most cases, the environment provides clues in the form of sunlight, activity, and temperature to help align this internal clock with the external environment. In situations when the two clocks are out of sync, individuals have difficulty sleeping during “conventional” sleep hours.
Circadian rhythm disorders can come in a variety of forms based on the pattern of the sleep clock misalignment, including:
- Night owl form (CRD-delayed sleep phase syndrome)
- Morning lark form (CRD-advanced sleep phase syndrome)
- Shift work disorder
- Jet lag
The misalignment between the internal clock and the environment can lead to a number of difficulties including insomnia, daytime sleepiness and fatigue.
Insomnia is the most common sleep disorder. Insomnia is defined as a recurrent problem initiating sleep, maintaining sleep, and/or waking up feeling un-refreshed, and is associated with problems functioning during the day. Daytime consequences for insomnia include irritability, fatigue, and inattention. The sleep field currently recognizes approximately 30 types of insomnia based on the presumed underlying cause for the sleep disruption.
Narcolepsy is a clinical disorder that involves a collection of symptoms. Chronic daytime sleepiness despite appropriate sleep opportunity is absolutely required for the diagnosis. At times, the desire to sleep becomes so overwhelming that small “cat naps” are required throughout the day to feel refreshed. Individuals may also experience episodes of cataplexy (muscle weakness associated with expression of emotion), muscle paralysis during sleep-wake transitions, and dream-like images experienced when they are awake.
What is Obstructive Sleep Apnea (OSA)?
Obstructive sleep apnea (OSA) is cessation of breath during sleep that lasts for at least 10 seconds, as a result of repetitive episodes of upper airway obstruction that occurs during sleep. This obstruction is usually associated with a fall in blood oxygen or arousal from sleep and may be caused by large tonsils or a large tongue, excess tissue in the upper airway, blocked nasal passages or the structure of the jaw and airway.
Patients with OSA may experience daytime symptoms such as sleepiness, fatigue, and problems with memory and concentration. Additionally, OSA can exacerbate other medical conditions such as high blood pressure, diabetes, heart problems, stroke, acid reflux and insomnia. Adequate treatment of sleep apnea can improve both symptoms and associated medical conditions.
How is OSA Diagnosed?
OSA is diagnosed using an overnight sleep study, called a polysomnogram (PSG). Although a patient’s symptoms and medical history can suggest they might have OSA, until a sleep study is done, the formal diagnosis cannot be made.
What to Expect During a Sleep Study
A sleep study is used to evaluate how a patient breathes during sleep. A trained technician will connect wires to parts of the patient’s head, chest, and legs in order to monitor the patient throughout the night, watching the oxygen level, breathing pattern, and sleep pattern.
The patient stays the entire night and should try to sleep as much as he/she normally does at home. The patient can bring items that will help him/her be more comfortable such as a pillow and pajamas. Patients must also bring all medications that they might need overnight.
Parasomnia literally means behaviors occurring at the time of sleep. In general, these behaviors occur during the transition from sleep-wake or during transitions within the different stages of sleep.
In most cases, parasomnias are infrequent and benign and do not require medical attention. A formal evaluation by a sleep specialist should be considered in the following situations:
- Episodes result in injury to the individual or others
- Episodes result in significant sleep disruption to the individual or members of their household
- Episodes result in significant daytime dysfunction.
Some of the conditions categorized as parasomnias include:
- Night terrors
- Sleep walking
- Bruxism (teeth grinding)
- Sleep-related eating disorders
- Somniloquy (talking in one’s sleep)
RLS is a disorder diagnosed by the presence of four essential symptoms:
- An uncomfortable sensation usually located in the legs that are associated with an overwhelming urge to move.
- The experience of these sensations when the individual is immobile or at “rest.”
- When the individual moves, the symptoms improve.
- The symptoms are most prominent at night.
Due to the nature of these clinical symptoms, individuals with RLS often experience difficulties sleeping at night and
Request an Appointment
Already a Patient?
Traveling for Care?
Whether you're crossing the country or the globe, we make it easy to access world-class care at Johns Hopkins.