DEAR MAYO CLINIC: My 10-year-old daughter is tired most of the time, but her blood work is normal and she gets plenty of sleep at night. Her pediatrician recommended a sleep study. What is involved in a sleep study, and what types of issues would doctors be looking for?

ANSWER: There are many possible reasons for your daughter’s symptoms. They may or may not be related to a sleep disorder. A sleep study could be helpful in uncovering the problem, but it’s not a good first step. Instead, your daughter should have a consultation with a physician who specializes in sleep medicine. Through that process, you can decide the best way to move forward.

Depending upon the nature of the sleep problem, the sleep specialist can order different types of sleep studies or tests. The most common test is a nocturnal polysomnogram. It involves the monitoring of brain waves, blood oxygen level, carbon dioxide level, eye movements, muscle activity, heart rate and breathing during sleep. Although a nocturnal polysomnogram is a valuable tool for identifying certain sleep disorders, it should not be used as a stand-alone test. Overnight oxygen analysis (oximetry) and actigraphy (assessment of activity and rest cycles in the home environment for up to two weeks) are other common types of sleep studies.

In a situation like your daughter’s, it’s important to have a sleep medicine specialist provide a comprehensive consultation before any testing is done. That consultation should include a conversation about symptoms and medical history, as well as a thorough physical exam. Based on the findings of that consultation, additional tests can be ordered if needed. They may or may not include a sleep study.

It is important to have a child evaluated if you suspect a sleep disorder. Sleep disorders in children are common, with about 30 to 40 percent having a sleep problem sometime during childhood. Most sleep problems are treatable.

Untreated sleep disorders can have a big effect on a child’s quality of life. Often children with sleep problems are tired, grumpy and inattentive at school. They also may have mood swings and show symptoms of hyperactivity. In some cases, children may even be misdiagnosed with attention deficit disorder.

The most common sleep disorder in children is obstructive sleep apnea. In many children, large tonsils that block the upper airway during sleep cause sleep apnea. A child with sleep apnea may snore, sleep restlessly, have problems breathing and wake frequently during the night. Removing the tonsils often solves the problem. However, some children may need a device called a continuous positive airway pressure, or CPAP, machine to help them breathe well when they sleep.

Restless legs syndrome frequently causes daytime sleepiness. Children with this disorder have creepy, crawly feelings in their legs at night that get worse if they keep their legs still. If they move their legs, the feeling temporarily goes away. Children with restless legs syndrome may wake hundreds of times during the night. As a result, even if they seem to sleep for eight to nine hours, they still feel very tired in the morning.

Narcolepsy —  a sleep disorder characterized by overwhelming daytime drowsiness and sudden attacks of sleep —  also can affect children. Sleep terrors, nightmares and sleep walking may lead to daytime sleepiness for some kids. Common disorders such as depression and anxiety can disrupt sleep, as well.

Investigating sleep problems and finding the cause depend heavily on a child’s symptoms and situation. It has become common for some sleep labs to perform sleep studies without a doctor actually seeing the patient. We do not use that approach at Mayo Clinic, nor do we recommend it.

If you go to a sleep center, it should be accredited by the American Board of Sleep Medicine. Make sure the sleep medicine specialist you consult is also board certified by the American Board of Sleep Medicine. Sleep specialists come from a variety of medical backgrounds, including neurology, pulmonary medicine and psychiatry. In your situation, it would be best to find a specialist with experience in pediatric sleep medicine. —  Suresh Kotagal, M.D., Center for Sleep Medicine, Mayo Clinic, Rochester, Minn.

Medical Edge from Mayo Clinic is an educational resource and doesn’t replace regular medical care. Email a question to medicaledge@mayo.edu. For more information, visit www.mayoclinic.org.