Daytime sleepiness can often be attributed to taking certain types of medications or ingesting chemicals such as caffeine or nicotine. The cause of daytime sleepiness may not always be this simple, however. Because daytime sleepiness can interfere with daily activities, interrupt work or school, and pose a danger to you and those around you, the underlying cause should be determined in order to find effective treatment.
Central Nervous System Disorders
Disorders that affect the functions of the central nervous system may cause daytime sleepiness. Hypersomnia is a rare disease that accounts for about 5 percent of excessive daytime sleepiness cases, according to the Encyclopedia of Mental Disorders. Patients with hypersomnia get adequate sleep at night but have trouble waking up in the morning. They experience increasing sleepiness through the day and do not feel refreshed even after taking naps. The exact cause of hypersomnia is not known.
Narcolepsy, as defined by the National Institute of Neurological Disorders and Stroke, is a chronic neurological disorder caused by the brain's inability to regulate sleep cycles. Narcoleptics experience a sudden onset of sleep accompanied with a loss of voluntary muscle tone and hallucinations.
Sleep Deficiencies
Those affected by conditions that result in sleep deficiencies will often experience excessive daytime sleepiness. Insomnia is the inability to fall asleep or to stay asleep, and is caused by a variety of factors, including stress, anxiety, depression, medications, eating schedules and poor sleep habits. The doctors at the Mayo Clinic report that one-third of all adults will experience insomnia at some point during their lives.
Sleep apnea is a condition characterized by one or more pauses in breathing or taking shallow breaths during sleep. These pauses may last from a few seconds to minutes, and can occur up to 30 times an hour, according to the National Heart Lung and Blood Institute. These pauses in breathing can cause disruptions in sleep that result in excessive tiredness during the day.
Circadian Rhythm Disturbances
Circadian rhythm is the body's natural 24-hour clock that regulates physical, mental and behavioral changes. The nerve cells in an area of the brain known as the suprachiasmatic nucleus control the circadian rhythm. Natural factors such as hormone release, as well as environmental signals such as light and dark, help to regulate circadian rhythms. When the rhythm is disturbed, such as in those suffering from significant time changes due to travel or working the night shift, daytime sleepiness often occurs.
