Intentional sleep deprivation is the leading cause of chronic sleepiness, while restless leg syndrome and sleep apnea are underlying conditions that can cause chronic sleepiness, notes WebMD. Other potential causes include obesity; lack of physical activity; and drug, alcohol and cigarette use.
People with restless leg syndrome have unpleasant sensations in their legs and strong urges to move them, states WebMD. Symptoms of the condition usually occur at night, leading to sleep deprivation and resulting in chronic sleepiness. Sleep apnea happens when the upper airway collapses hundreds of times for at least 10 seconds. When the airway collapses or is obstructed, breathing is interrupted, leading to sleep disruptions and chronic sleepiness.