Drowsiness is a state of decreased awareness or alertness associated with a desire or tendency to fall asleep.
Almost everyone has felt drowsy before, usually due to normal tiredness from a long day or lack of sleep. There are other causes of this condition as well. Most of the causes are not serious, but some are life threatening.
When someone complains of abnormal drowsiness, the healthcare professional will ask questions, such as: how long it has been presentwhether it occurs all day every day or only on some dayswhether it is getting worse, better, or staying the samethe number of hours of sleep the person gets every night and whether there is any trouble with sleepingthe amount of stress in the person's lifethe amount of activity or exercise a person engages inthe person's dietany other symptoms the person is having, such as weight loss, fever, or confusionwhat medications, drugs, or herbs a person takes, if anywhat other medical problems a person has, if any
There are many possible causes of this condition, including: lack of sleep or sleep disorders, such as insomnia and sleep apnea. Sleep apnea is a disorder of breathing during sleep that prevents a person from getting enough rest.infections, such as chronic bronchitis or infectious mononucleosisa low red blood cell count, called anemiastressworking, studying, or exercising too muchlack of exercise or poor physical conditioninghormone imbalances, such as hypothyroidism, a condition caused by a low level of thyroid hormonedepression or other psychological disordersautoimmune disorders, that is conditions in which a person's immune system attacks his or her own body. Examples include systemic lupus erythematosus and rheumatoid arthritis.low oxygen levels in the blood, which can occur with heart disease or chronic obstructive pulmonary diseasetoxin or chemical exposure, such as carbon monoxide poisoningmedications, such as antihistamines, sedatives, and certain medications used to treat depression or high blood pressurealcoholsystemic disorders, such as uncontrolled diabetesa stroke, ("brain attack")any severe, life-threatening illness, such as meningitis, severe pneumonia, or end-stage cancer
Other causes are also possible. Sometimes no cause can be found.
Avoiding stress and overexertion, getting enough sleep, and eating a healthy diet can prevent many cases of drowsiness. Avoidance of alcohol and medications that cause drowsiness can avoid cases due to these causes. Maintaining a normal weight and avoiding obesity can sometimes prevent sleep apnea. Many causes cannot be prevented.
After a physical examination, the healthcare professional may order further tests. A chest x-ray may be done if lung disease is thought to be the cause. A sleep study, called polysomnography, may be done if sleep apnea is suspected. A complete blood count (CBC) may be ordered if anemia or an infection is suspected. Other tests may also be needed in some cases.
Drowsiness, when persistent, can limit a person's ability to work, go to school, and drive. Severely affected people may need to rest for most of the day. Other long-term effects depend on the cause. For instance, end-stage cancer often results in death. Cases due to a stroke may cause permanent drowsiness and other limitations from brain damage.
Drowsiness is not contagious and poses no risk to others. However, if the cause is an infection, such as meningitis, the infection may be contagious.
Specific treatment is directed at the cause. For instance, a person may need to get antibiotics for an infection or thyroid hormone medication for a low thyroid level. In others, control of diabetes or other systemic disorders may be needed. A person with depression often needs medications to treat the condition. Those with cancer may need surgery, chemotherapy, or radiation therapy.
All medications and surgeries have possible side effects. For instance, antibiotics may cause allergic reactions and stomach upset. Surgery can be complicated by bleeding, infection, or reactions to anesthesia.
If the drowsiness goes away, a person may or may not need further treatment. For instance, those with kidney failure need further treatment even if their drowsiness goes away. Those who were "overdoing it" or not getting enough sleep may need no further treatment once they get some rest. Those with serious diseases, such as end-stage cancer, may die if treatment is unsuccessful.
Any new or worsening symptoms should be reported to the healthcare professional. The cause of drowsiness may or may not need monitoring. For instance, those with anemia need a repeat CBC to make sure the blood count has returned to normal.
Harrison's Principles of Internal Medicine, 1998, Fauci et al.