Insomnia and excessive daytime sleepiness can be caused by other sleep, medical and psychiatric disorders.
Other Sleep Disorders That Cause Insomnia Symptoms
Some sleep disorders can cause insomnia symptoms, so these disorders should be assessed in every patient who presents with insomnia symptoms:
- Restless leg syndrome or delayed sleep phase syndrome may cause difficulty with falling asleep.
- Sleep apnea or periodic limb movements during sleep may cause frequent awakening at night.
- Sleep apnea or advanced sleep phase syndrome may cause early morning awakening.
Psychiatric and Physical Disorders
Psychiatric and physical conditions can trigger or contribute to chronic insomnia. For example, people with depression often wake up earlier than they previously did and those with anxiety or posttraumatic stress disorder often have difficulty falling asleep. Acute pain or physical conditions that cause discomfort can also exacerbate insomnia symptoms. It is important to emphasize that as insomnia becomes chronic, it often decouples from these conditions and is perpetuated by insomnia-specific psychopathological factors. Additionally, there are often shared behavioural pathways that worsen the symptoms of both insomnia and the comorbid conditions.
Medications such as antidepressants, CNS stimulants, CVS antihypertensive medications including beta blockers, OTC decongestants, GI irritant medications and corticosteroids can cause insomnia. Also consider the rebound effect of withdrawal from sedating agents such as alcohol and short-acting hypnotics.
Excessive daytime sleepiness
Sleep restriction or insufficient sleep is the most common cause of excessive daytime sleepiness in healthy people.
There are two main types of sleep apnea. Obstructive sleep apnea involves partial or complete upper airway occlusion at least five times per hour for 10 seconds or more, resulting in a minimum 50 per cent decrease in airflow (hyponea) or in no airflow (apnea). Central sleep apnea is far less common. It features intermittent cessations of breathing resulting from an absence of the neural drive for breathing.
Although people with sleep apnea may apparently sleep through the night, their sleep is fragmented by short arousals following apneic episodes, and they awake with a sense of having had unrefreshing sleep. They often complain of morning headaches (possibly as a result of a rise in carbon dioxide), which often resolves as the day progresses. They also often feel daytime fatigue. In contrast to people with sleep deprivation or narcolepsy, where napping is very refreshing, people with sleep apnea feel tired when they wake up from naps.
STOP-BANG questionnaire for sleep apnea screening
A simple screening tool to detect sleep apnea is STOP, a mnemonic that stands for the following questions:
Has anyone Observed you stop breathing in your sleep?
Score 1 point for each “yes” answer. The predicted probability of someone with a score of 3 having obstructive sleep apnea is about 70 per cent. The probability increases as the score increases, with a probability of 80 per cent at a score of 6, and 85 per cent at a score of 7 or 8.
Narcolepsy is a rare condition caused by a lack of orexin/hypocretin, a sleep-regulating hormone that promotes wakefulness, alertness and vigilance. The leading symptom is excessive daytime sleepiness with short (10–20 minute) naps, or sudden, irresistible sleep attacks from which the person wakes up refreshed.
There are two types of narcolepsy:
- Type 1 is narcolepsy with cataplexy, which involves loss of muscle tone associated with strong emotional states.
- Type 2 is narcolepsy without cataplexy.
People with narcolepsy may also experience sleep paralysis (brief inability to move on awakening) and sleep-related hallucinations. The condition may be genetic, autoimmune, post-H1N1 or posttraumatic in origin.
Periodic Limb Movement Disorder
Periodic limb movement disorder features repeated leg twitches during sleep. It fragments sleep with frequent leg movement–related arousals and is more common in older age, vertebral degenerative disorders, pregnancy, Parkinson’s disease and chronic kidney disease. The rate of the disorder is increased four-fold in people who take selective serotonin reuptake inhibitors (SSRIs). It also occurs with iron deficiency (low ferritin) and vitamin B12 deficiency, and may occur even at the lower end of the normal range for ferritin levels.
Substance or Medication Use
Drugs such as benzodiazepines, opioids, methadone, cannabis, antihistamines and alcohol, as well as withdrawal from stimulants, including caffeine, should be considered as possible causes of excessive daytime sleepiness.
Systemic infections are a common cause of excessive daytime sleepiness. Neurological disorders (infections, epilepsy, head injury) and metabolic disorders that affect the central nervous system (e.g., diabetes, thyroid disease) are also associated with excessive daytime sleepiness.
Although depression is usually comorbid with insomnia, 20 percent of people who are depressed describe fatigue and excessive sleepiness. Atypical depression is characterized by hypersomnia. Posttraumatic stress disorder may induce pathological sleep architecture and cause fragmented sleep, depriving the person of the restorative properties of sleep.
Circadian Rhythm Disorders
Circadian rhythm disorders involve a discrepancy between the person’s natural sleep schedule (dictated by one’s body clock) and the schedule that is considered the norm for school, work or other obligations. The most common circadian problem seen in primary care involves patients who are shift workers.
A common problem that can begin in the teenage and young adult years is delayed sleep–wake phase disorder. The sleep–wake cycle is shifted to an early morning bedtime and mid-day wake-up time. People with the disorder have difficulty getting up in the morning on school or work days and experience excessive sleepiness until the afternoon. The condition may persist into middle adulthood and is often misdiagnosed as insomnia.
In addition to taking a detailed sleep and mental health history, you can refer the patient to a sleep specialist to measure melatonin secretion that can distinguish between delayed sleep–wake phase disorder and going to bed late due to social reasons, insomnia or mental health conditions.
Other conditions and factors that can cause excessive daytime sleepiness include idiopathic hypersomnia, post-viral hypersomnia, genetics and Kleine-Levin syndrome (adolescent hyperphagia, aggression and hypersexuality).