Sleep apnea, narcolepsy, depression and restless legs disorder can cause excessive sleepiness, notes WebMD. Not getting enough sleep also leads to excessive fatigue. Polysomnography, electroencephalogram and genetic blood testing are available to diagnose sleep disorders, explains Healthline.
Sleep apnea happens when the upper airway closes for at least 10 seconds during sleep, doing so up to hundreds of times during sleep, according to WebMD. When the brain doesn't send signals to the muscles that control breathing, central sleep apnea occurs. Blockage in the airway leads to obstructive sleep apnea. It is associated with high blood pressure, depression, diabetes and heart disease.
Narcolepsy involves many uncontrollable sleep episodes throughout the day, states WebMD. It is marked by entering rapid-eye movement, or REM, sleep without warning and a sudden loss of muscle control. This can be a slight weakness or an entire body collapse. Often it is triggered by emotional distress or fatigue.
Several sleep disorders, including insomnia, restless legs syndrome and obstructive sleep apnea, are linked to depression. It is unclear whether depression leads to excessive fatigue or if excessive fatigue causes depression, WebMD explains.
Characterized by an uncomfortable urge to move one's legs, restless legs syndrome cause spasms every 20 to 30 seconds throughout a person's sleep, claims WebMD. Treatment may include taking iron, vitamin B or folate supplements, avoiding alcohol and caffeine before bed, and exercising regularly.