What could cause excessive daytime drowsiness?

There are many possible causes of excessive daytime drowsiness. Some of the common causes are: 
  • poor sleep at night -- often from shift work or a poor sleep schedule
  • chronic medical illnesses such as heart failure, diabetes or kidney disease
  • mental disorders such as anxiety or depression
  • drug use such as caffeine or certain medications
  • a sedentary lifestyle
Sleeping disorders such as obstructive sleep apnea or narcolepsy may also cause excessive daytime drowsiness. Often there is a combination of several factors that contribute to excessive daytime drowsiness. 
Howard E. Lewine, MD
The most common cause of excessive daytime drowsiness is sleep apnea.

Sleep apnea affects about 18 million adults in the United States. It is most common among overweight men. With sleep apnea, the airway becomes blocked or breathing muscles stop moving. Breathing temporarily stops or becomes shallower. This can happen hundreds of times each night.

The clues that you may have sleep apnea include:
  • Loud snoring four or more times per week
  • Someone telling you that you periodically stop breathing or gasp for air during your sleep
  • Daytime drowsiness, just as you describe
  • Morning headaches
  • A large neck (collar size); 17 inches or more in men, 16 inches or more in women
  • History of high blood pressure
People with untreated sleep apnea can have difficulty concentrating and are more likely to get into traffic accidents. Sleep apnea can lead to an enlarged heart and heart failure.

If you suspect that you may have sleep apnea, talk with your doctor. The usual test to confirm the diagnosis is a sleep study called a polysomnogram.

A much less likely reason for your symptoms is narcolepsy. People with narcolepsy can fall asleep any time, even when they are standing up and active. It is an uncommon disorder.
Harvard Medical School Improving Sleep: A guide to a good night's rest

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.