Sleep disorder is a collective term referring to conditions that impact sleep quality, timing, or duration and impact a person’s ability to properly function while they are awake. These disorders can contribute to other medical problems, and some may also be symptoms for underlying mental health issues. Over 100 different sleep disorders have been identified, most of which are characterised by one or more of the following four signs:

  • Trouble falling or remaining asleep

  • Finding it difficult to stay awake during the day

  • Imbalances in the circadian rhythm that interfere with a healthy sleep schedule

  • Propensity to unusual behaviours that disrupt sleep

Insomnia

According to the American Academy of Sleep Medicine, insomnia is defined as “persistent difficulty with sleep initiation, duration, consolidation or quality.”

  • Sleep-onset insomnia refers to difficulty falling asleep. Sleep maintenance insomnia refers to difficulty staying asleep after initially nodding off.

  • Ingestion or consumption of substances that negatively affect sleep, chronic medical conditions, social isolation, use of prescription medications, as well as factors like unhealthy sleep habits and stress are common causes of insomnia across all age groups.

  • Some studies estimate that 10% to 30% of adults live with chronic insomnia. For other studies, this figure is closer to 50% to 60%.

  • Studies suggest that insomnia affects 30% to 48% of older people, up to 23.8% of teenagers and more than 50% of pregnant women.

  • The most common symptoms among chronic insomnia patients include difficulty falling and/or staying asleep, waking up earlier than planned, and not feeling tired or ready for bed at scheduled times. Common daytime impairments include fatigue and malaise, memory and concentration difficulties, mood disturbances and irritability, and behavioral problems such as hyperactivity and aggression.

Parasomnias

Parasomnias involve abnormal movements, behaviours, emotions, perceptions, and dreams that occur while falling asleep, sleeping, between sleep stages, or during arousal from sleep. Parasomnias are dissociated sleep states which are partial arousals during the transitions between wakefulness, NREM sleep, and REM sleep, and their combinations.

  • Confusional arousals: Those who experience confusional arousals will exhibit confused behaviour in bed due to an incomplete arousal from deep sleep. They may not react to other people who attempt to intervene and have little to no memory of the event.

  • Sleepwalking: Also known as somnambulism, sleepwalking occurs when people get out of bed and move about while still asleep. Sleepwalkers may remain in their bedrooms, but some travel to other areas in or outside of their residence.

  • Night terrors: Sleepers experiencing night terrors often cry or act out in their sleep but will have little to no memory of the incident after waking. Most night terror episodes are brief, but they can last for several minutes in some cases.

  • Sleep-related sexual abnormal behaviours: People with this condition will display aggressive or uncharacteristic sexual behaviour while asleep, but will generally will remember very little, if any, of their behaviour on awakening.

  • REM sleep behaviour disorder (RSBD or RBD): Sleepers with this disorder physically or vocally act out on their dreams. The behaviours associated with this disorder can disrupt sleep for the individual and their partner, and also put people at higher risk of physical injury.

  • Sleep paralysis: Sleep paralysis causes people to feel completely paralysed as soon as they wake up. This may also occur during sleep onset. Paralysis episodes usually don’t last for more than a few minutes, but this condition can trigger sleep anxiety for some people.

  • Nightmare disorder: While isolated nightmares are common for most people, nightmare disorder is defined by vivid, unpleasant dreams that disrupt sleep on a recurrent basis. For some, the nightmares become increasingly disturbing. People with nightmare disorder often experience anxiety about going to bed, as well as post-awakening anxiety when the dream ends.

  • Exploding head syndrome: As the name implies, people with this condition will imagine loud explosions in their head when they are aroused from sleep. People may physically or vocally act out toward the explosion, but they will not actually feel any pain.

  • Sleep-related hallucinations: Some people experience hallucinations during sleep onset or during the transition between sleep and waking. These hallucinations can be so vivid for sleepers that they will attempt to leave their bed, putting them at higher risk of injury.

  • Sleep enuresis: Also known as bedwetting, sleep enuresis is involuntary urination during sleep. Enuresis is considered a parasomnia for children and adults over the age of five who experience episodes at least twice a week for at least three months.

Sleep-Related Breathing Disorders

These disorders are characterised by abnormal breathing during sleep, including snoring. For some, the individual will also experience abnormal breathing while they are awake.

  • Obstructive sleep apnea: Obstructive sleep apnea (OSA) is characterized by disordered breathing episodes, or apneas, during sleep. People with this condition will often wake up choking or gasping for air multiple times during the night, and report feelings of fatigue and non-restorative sleep during the day. OSA occurs when the airway is blocked due to certain physiological factors, such as a narrow throat, large tongue, smaller lower jaw, or obesity. Children may experience OSA if they have not had their tonsils or adenoids removed.

  • Central sleep apnea: Much like OSA, central sleep apnea, or CSA, causes apnea breathing episodes during the night. The key difference is root cause. CSA occurs when the brain stops sending signals to muscles that regulate breathing, rather than a physical obstruction blocking the airway. Strokes and other medical conditions that affect the brain stem can cause CSA, as can obesity, heart failure, and some medications.

  • Sleep-related hypoventilation disorders: These disorders occur when sleepers do not receive enough ventilation, causing the carbon dioxide levels in their blood to spike. Obesity, genetic abnormalities, certain drugs and medications, and underlying medical conditions can all lead to sleep-related hypoventilation.

  • Sleep-related hypoxemia disorder: Hypoxemia refers to below-normal blood oxygen levels. For people with this condition, their blood oxygen levels decrease primarily during sleep. Sleep-related hypoxemia may be a symptom of an underlying medical condition such as pulmonary hypertension, chest wall disorders, or neurologic and neuromuscular disorders.

Hypersomnolence Disorders

Hypersomnolence refers to feelings of sleepiness and fatigue during the day despite a healthy circadian rhythm and an adequate amount of sleep the previous night. These feelings may lead to involuntary lapses into drowsiness or sleep, which in turn puts people at risk for accidents. Some people with hypersomnolence disorders feel the effects of daytime sleepiness before nodding off, while others will unknowingly fall asleep.

  • Narcolepsy: This disorder occurs when patients with normal sleep schedules either feel the irrepressible urge to sleep or involuntarily lapse into sleep on a daily basis for at least three months. This condition falls into two primary categories. Narcolepsy Type 1 includes cataplexy, a sudden muscle weakness or paralysis, whereas Narcolepsy Type 2 may include some muscle weakness but not to the same extent.

  • Idiopathic Hypersomnia: This condition, like narcolepsy, is characterised by the strong urge to fall asleep or lapses into sleep despite an otherwise healthy sleep schedule. However, idiopathic hypersomnia does not include cataplexy.

  • Kleine-Levin Syndrome: This rare disorder is defined by episodes of excessive sleep – up to 20 hours a day in some cases. The first episode often occurs in tandem with a bodily infection or excessive alcohol intake. Episodes can persist for days, weeks, or even months. Common effects of Kleine-Levin Syndrome include cognitive dysfunction, altered perceptions, eating disorders, and disinhibited behaviours.

Sleep-Wake Disorders

This category of circadian rhythm sleep disorders is tied to a person’s internal clock and the factors that regulate their 24-hour sleep cycle. Sleep-wake disorders occur in people whose circadian rhythms are misaligned, causing them to feel alert and tired at abnormal times of the day.

  • Sleep-wake phase disorder: This disorder is defined by the inability to fall asleep and wake up at the intended times, and falls into two subcategories. Delayed sleep-wake phase disorder occurs when the patient’s sleep-wake cycle is delayed by at least two hours. For advanced sleep-wake phase disorder, patients fall asleep and wake up at least two hours ahead of schedule.

  • Irregular rhythm sleep-wake disorder: This disorder is marked by irregular sleeping and waking episodes over a 24-hour period. Patients often experience insomnia symptoms when they are trying to sleep and excessive daytime sleepiness.

  • Non-24 hour sleep-wake disorder: People with this disorder have internal clocks that do not follow a 24-hour schedule. Their sleep-wake cycle may be shorter or longer than 24 hours, depending on how their circadian rhythm is synchronised. Most patients with non-24 sleep-wake disorder are totally blind.

  • Shift work sleep disorder: Most people with shift work sleep disorder have jobs that require shifts outside the typical 9 to 5 schedule, including evening and overnight shifts. They experience insomnia symptoms at night and excessive daytime sleepiness because their sleep schedule is not in sync with a normal 24-hour circadian rhythm, which is influenced by light and darkness. Shift work sleep disorder often deprives people of one to four hours of sleep every 24-hour period.

  • Jet lag disorder: This temporary disorder occurs when travellers pass through multiple time zones during a single flight or series of successive flights, leaving their circadian rhythm out of sync with local time at their final destination. The severity of jet lag depends on the length of travel, as well as direction.

Sleep-Related Movement Disorders

These disorders are characterised by abnormal movements during sleep that can be disruptive for the individual, as well as their sleep partner. They often cause excessive daytime sleepiness and fatigue due to sleep loss.

  • Restless legs syndrome (RLS): Also known as Willis-Ekbom disease, this disorder causes people to experience unpleasant or painful sensations in their legs. These sensations are usually more pronounced at night when the individual sits or lies down for prolonged periods. RLS creates strong urges to move the legs in order to alleviate discomfort.

  • Periodic limb movements disorder (PLMS): People with PLMS experience periodic bodily movements during the night that coincide with arousal and sleep disruptions. In most cases, movements are isolated to the lower limbs. Patients are often unaware of the movements

  • Sleep-related bruxism: Sleep-related bruxism causes people to grind their teeth during sleep. Over time, this can cause excessive jaw pain, abnormal tooth wear, and other side effects.

Sources: The Sleep Foundation | Wikipedia | National Library of Medicine