Sleeping Problems: Hypersomnia, Somnolence Syndrome, and Nightmares

Approved by the Cancer.Net Editorial Board, 10/2020

Cancer and cancer treatment can affect your sleep. One sleeping problem is insomnia. This is when you cannot fall asleep or stay asleep, and it is discussed in another article on this website. There are other sleeping problems a person can experience when they have cancer. Some of these sleeping problems include:

  • Hypersomnia

  • Somnolence syndrome

  • Nightmares

Side effects from cancer or the treatment you are receiving, your emotional health, and medical conditions unrelated to cancer can all cause sleeping problems. It is important that you tell your health care team if you have any sleeping problems or if you experience sleeping changes over time. That's because good sleep is necessary for your health.

Managing side effects is an important part of cancer care and treatment. This is called palliative care or supportive care. Talk with your health care team about managing your sleeping problems.

What is hypersomnia? What are the signs of hypersomnia?

People with hypersomnia feel very sleepy during the day or want to sleep for longer than normal at night. Hypersomnia may also be called somnolence, excessive daytime sleepiness, or prolonged drowsiness.

The signs of hypersomnia can include:

  • Sleeping for 10 or more hours a time

  • Excessive amounts of deep sleep

  • Trouble staying awake during the day

  • Sleepiness that is not reduced after sleeping or taking a nap

Hypersomnia may interfere with your relationships. It can make it hard to take care of family, home, and work responsibilities. You may find it difficult to enjoy activities because you are so sleepy.

Hypersomnia and fatigue are similar, but they are not the same. Hypersomnia is feeling too sleepy during the day and includes sleeping for a long time at night. Fatigue is a lack of energy and exhaustion that is not relieved by sleep.

What causes hypersomnia?

Not getting enough sleep at night is one of the most common causes of hypersomnia and excessive sleepiness during the day. You can have insomnia at night and sleepiness during the day.

Cancer, cancer treatment, and other conditions can cause hypersomnia. The cancer-related causes of hypersomnia are:

  • Anemia, which is a low number of red blood cells

  • Anxiety or depression

  • Chronic pain

  • High calcium levels, which is called hypercalcemia

  • Hormone level changes, including hypothyroidism, which is when the thyroid gland does not make enough thyroid hormones

  • Low potassium levels, also called hypokalemia

  • Some types of chemotherapy

  • Tumor in your brain and central nervous system (CNS), either because that is where the tumor started or if the cancer has spread there from another part of the body

Some prescription and over-the-counter (OTC) medications can cause hypersomnia, such as:

  • Some antidepressants

  • Medications to manage nausea

  • Medications to manage pain, including opioid medications

  • Sedatives, which are medications that calm you down or make you sleep

  • Antihistamines, which are medications used to treat allergy or cold symptoms

  • Sleeping pills

How is hypersomnia managed?

To treat hypersomnia, your doctor first needs to find and treat the cause. For example, hypersomnia related to chemotherapy usually improves after treatment ends. If another medication is causing the hypersomnia, your doctor may be able to change your medication or the dose. You could be prescribed a stimulant medication.

With any sleep disorder, it is important that you have healthy sleep habits at home. This is often called "sleep hygiene." This can help you improve your hypersomnia or other sleep problems.

These changes can help you manage hypersomnia:

  • Sleep a few hours longer at night to avoid excessive sleepiness during the day

  • Exercise daily in the morning or early afternoon, instead of near bedtime

  • Do enjoyable activities during the day that require your full attention

  • Try to go to sleep and wake up at the same time every day

  • Only use your bed for sleeping and sex

  • Avoid eating a heavy meal or drinking a lot of liquid in the evening

  • Avoid alcohol and caffeine

What is somnolence syndrome? What are the signs of somnolence syndrome?

Somnolence syndrome is a type of hypersomnia in children. It is linked to receiving radiation therapy to the head.

The symptoms of somnolence syndrome usually happen 3 to 12 weeks after radiation therapy ends. It can last a few days or several weeks. The symptoms include:

  • Excessive drowsiness

  • Sleeping up to 20 hours a day

  • Headaches

  • Low-grade fever

  • Loss of appetite

  • Nausea and vomiting

  • Irritability

Nightmares/vivid dreams and cancer

Nightmares are vivid, frightening dreams. They usually cause the person to wake up and remember part or most of the dream.

Most people have nightmares from time to time. The frequency of nightmares and other vivid dreams can increase after a cancer diagnosis and during cancer treatment. Frequent nightmares can lead to a fear of going to sleep, restless sleep, and daytime sleepiness.

Emotional stress, anxiety, and depression are common causes of nightmares. A cancer diagnosis, treatment, or anxieties you experience as a cancer survivor can all increase your emotional stress. Financial concerns and worry for your family may also be causing nightmares.

Other causes of nightmares that you can experience during cancer care include:

  • Certain antibiotics

  • Iron supplements

  • Pain medications

  • Heart medications

  • Withdrawal from alcohol, pain medications, and some anti-anxiety medications

  • Unrelieved pain

Having cancer can be frightening and stressful. It is normal to experience nightmares during treatment and recovery. But if you are experience too many nightmares that interfere with your sleep or cause anxiety, it is important to talk with your health care team to find relief and get better sleep.

These tips can help you cope with nightmares:

  • Be honest about your fears and feelings about cancer. Discuss them with a family member, friend, or counselor early in the day, rather than at night.

  • Talk about your specific nightmares with a family member, friend, or counselor.

  • Find creative ways to express what happens in your nightmares, such as writing about them or drawing. This can be done on your own or with an art therapist.

  • Make up different endings or story lines to the nightmares. Visualize these endings.

Questions to ask your health care team

  • If I have sleeping problems such as excessive sleep or nightmares, who should I tell on my health care team?

  • Could these sleeping problems be a side effect of my cancer, treatment, or medication?

  • What changes to my daily habits would you recommend for better sleep?

  • Are there treatments or medications that could help relieve my sleep problem?

Related Resources

8 Steps to a Restful Night's Sleep


Sleeping Problems: Insomnia