All of us have the experience of feeling tired at times, but roughly 20 to 30% of the population can have excessive daytime sleepiness. The two commonest complaints that cause patients to seek treatment at a Sleep Disorders Clinic are insomnia (not being able to sleep at night) and excessive daytime sleepiness (EDS).
People who have excessive sleepiness feel drowsy and sluggish most days and these symptoms often interfere with their daily functioning. Their work, school, activities, or relationships can be affected by their sleepiness. EDS is different from fatigue which is characterized by low energy and the need to rest (not necessarily sleep).
Fatigue is a subjective feeling of tiredness. It may be sudden or gradual in onset. It is a normal phenomenon if it follows prolonged physical or mental activity, and resolves completely with rest. It may be a symptom of one of many medical conditions if it prolonged, severe, progressive, or occurs without provocation.
EDS is also different from depression, in which a person may have a reduced desire to do normal activities, even the ones they used to enjoy. Anhedonia is the term that describes an inability to derive pleasure from activities that would normally give us pleasure. It is a cardinal feature of depression.
Excessive sleepiness is a serious symptom that can have many different causes. The common causes are:
- Poor sleep habits - reduced opportunity for sleep or irregular sleep schedule,
- Sleep disorder - obstructive sleep apnea,
- Side effects from certain medications,
- Other underlying medical conditions (e.g., hypothyroidism).
