The experience of being sleepy during the day from time to time is almost universal. However, being sleepy during the day is a problem when it happens often or every day and interferes with quality of life. There are many causes for chronic excessive sleepiness, such as poor sleep habits, medication side-effects, sleep disorders and other medical conditions. It is important to identify the specific cause(s) of an individual’s sleepiness in order to correct the problem.

Not Enough Sleep

Most human adults require an average of eight hours of sleep per night in order to be rested. The circumstances of our lives, however, often prevent us from obtaining a healthy amount of sleep every night. As we deprive ourselves of one or two hours some nights during a week, we create a sleep deficit which results in daytime sleepiness.

Abnormal Sleep

While we do not fully understand all that sleep does for us, it is clear that our bodies require adequate sleep time and quality to maintain health. The brain works hard while we sleep, going through a series of processes that restore our feeling of alertness and sense of well-being. When these processes are interrupted, the result is daytime fatigue.

Most of the known sleep disorders cause disruption of the sleep processes. Examples of such sleep disorders are Obstructive Sleep Apnea and Periodic Limb Movements. An overnight sleep study, or polysomnogram, is required to diagnose and/or rule out the presence of sleep disorders that disrupt sleep.

Illness and Injury

Short and long term illness will cause excessive daytime sleepiness and fatigue. The pain experienced because of injuries and illness can disrupt sleep just as a sleep disorder does. Disrupted sleep, no matter what the cause, results in daytime sleepiness. Significant head trauma and neurological conditions may also result in excessive sleepiness.

Medications

There are many medications which are known to cause excessive sleepiness. Some can cause sleep apnea, which in turn causes daytime sleepiness. Simply stopping or changing the medication can result in improvement. However, when stopping or changing the drug is not an option, there are additional medications available that may help with the sleepiness.

Narcolepsy

Narcolepsy is a very specific medical disorder which causes excessive daytime sleepiness. This disorder is caused by a deficiency in a neuropeptide in the brain called hypocretin. Another symptom produced by this deficiency is episodic weakness. Narcolepsy is treated with medication and must be diagnosed via a special “sleep” test conducted during the day.

Idiopathic (no one knows)

Sometimes none of the above problems are the cause of a person’s excessive daytime sleepiness. When a cause cannot be determined, the disorder is called “idiopathic”. In many cases idiopathic sleepiness can be improved with certain treatments even though the primary cause is never recognized.