Everyone experiences occasional tiredness and sleepiness. But if you frequently feel tired and sleepy, it's important to determine the cause of this troublesome symptom. Insufficient sleep, sleep disorders, mental health issues, lifestyle choices, and medication and other substance use account for roughly 80 percent of cases of frequent or persistent tiredness. A wide range of medical conditions, such as infections and metabolic disorders, account for the other 20 percent of cases.
Insufficient sleep is the leading cause of excessive daytime sleepiness, or hypersomnia. Sleep requirements vary among individuals and across the lifespan. The National Sleep Foundation recommends 7 to 9 hours of sleep nightly for adults aged 18 to 64, and 7 to 8 hours for seniors aged 65 or older. Unfortunately, many Americans do not get enough sleep. According to a study published in the March 2011 issue of "Morbidity and Mortality Weekly Report," 35 percent of U.S. adults report getting less than 7 hours of sleep nightly, on average. Insufficient sleep can lead to daytime sleepiness and tiredness, and contribute to serious, long-term health problems.
Daytime sleepiness is the most common symptom associated with sleep disorders. Obstructive sleep apnea-hypopnea syndrome (OSAHS) is the most common sleep disorder, affecting 3 to 7 percent of men and 2 to 5 percent of women, as reported in the February 2008 issue of the "Proceedings of the American Thoracic Society." OSAHS is characterized by multiple episodes of partial or complete upper airway obstruction each hour while sleeping. These episodes trigger arousal to a lighter level of sleep or complete awakening. The resulting fragmented sleep is less restful than normal sleep and leaves the suffer chronically tired.
Tiredness and hypersomnia also occur with other less common sleep disorders, all of which interfere with restful sleep. Examples include:
-- Periodic limb movement disorder, characterized by involuntary movement of the legs or arms while sleeping
-- Narcolepsy, a long-term neurologic condition that features severe hypersomnia and daytime sleep "attacks"
-- Circadian rhythm disorder, a condition caused by disruption of a person's normal wake-sleep cycle, such as occurs in people who work night shift
Medication Side Effects and Substance Abuse
Drowsiness and tiredness are relatively common side effects of many medications. Adjusting the dose or switching to different medication may be helpful, but don't make any changes without first talking with your doctor. The list of possible culprits encompasses several drug categories. Examples include:
-- Antihistamines, such as diphenhydramine (Benadryl)
-- Sedatives, such as diazepam (Valium), lorazepam (Ativan) and secobarbital (Seconal)
-- Opioid pain medications, including oxycodone (Oxycontin, Percocet), fentanyl (Duragesic) and merperidine (Demerol)
-- Antiseizure drugs, such as phenytoin (Dilantin), ethotoin (Peganone) and ethosuximide (Zarontin)
-- Antidepressants, including fluoxetine (Prozac), paroxetine (Paxil) and sertraline (Zoloft)
-- Heart and blood pressure medications, such as atenolol (Tenormin), nadolol (Corgard), metoprolol (Lopressor), prazosin (Minipress) and Doxazosin (Cardura)
Use of alcohol and other mind-altering substances is often responsible for daytime sleepiness. Alcohol disrupts the sleep cycle, causing frequent awakenings that reduce the restfulness of sleep. People who regularly use alcohol to fall asleep or otherwise abuse alcohol commonly suffer from hypersomnia. Recreational or medicinal marijuana use can also cause drowsiness. Abuse of stimulants, such as amphetamine and cocaine, typically cause a rebound period of intense sleepiness after the drug effects have worn off.
Mental Health Disorders
Several mental health disorders, particularly mood and anxiety disorders, can leave people feeling tired and lacking energy. The authors of a review of relevant medical studies, published in October 2016 in "BMC Family Practice," found more than 18 percent of people seeking medical evaluation for tiredness were suffering from current depression. Bipolar disorder can also cause daytime sleepiness during the depressive phase. Anxiety disorders are another consideration, as these conditions often cause insomnia. The chronic lack of sleep can cause profound tiredness and irritability. Successful treatment of these mental health disorders often alleviates excess sleepiness, although it may take some time before significant improvement occurs.
Persistent tiredness and sleepiness can occur with numerous medical conditions, some far more common than others. While a complete list is too extensive to cover, some examples of conditions that might be to blame include:
-- Blood disorders: anemia, leukemia and lymphoma
-- Infections: infectious mononucleosis, HIV/AIDS and Lyme disease
-- Heart and lung conditions: chronic obstructive pulmonary disease and heart failure
-- Neurologic conditions: multiple sclerosis, dementia, Parkinson disease, stroke and traumatic brain injury
-- Gastrointestinal conditions: Crohn disease, ulcerative colitis and celiac disease
-- Inflammatory diseases: fibromyalgia, chronic fatigue syndrome, giant cell arteritis and rheumatoid arthritis
-- Endocrine disorders: diabetes, hypothyroidism and adrenal insufficiency
-- Solid tissue cancers: lung, colon, breast, prostate, pancreas and others
-- Other: Kidney and liver failure, severe malnutrition, and toxin ingestion, such as lead
Next Steps and Precautions
See your doctor as soon as possible if you experience frequent or persistent daytime sleepiness and tiredness. Because of the extensive list of possible causes, evaluation by a medical professional is needed for an accurate diagnosis and appropriate treatment. It's particularly important to see your doctor if your tiredness is accompanied by possible warning signs, including unintentional weight loss, shortness of breath, or insufficient energy to perform everyday tasks.
Reviewed and revised by: Tina M. St. John, M.D.