How does a doctor determine the cause of insomnia, and what investigations are necessary?

Doctor's Answer

The following common causes of insomnia can be remembered by using the mnemonic: INSOMNIAC.

  • I stands for illness due to a medical condition (asthma, congestive heart failure, chronic pains, cancer, acid-reflux disease (GERD), chronic obstructive lung disease, joint pains).
  • N stands for neurologic or psychiatric disorders (depression, bipolar disorder, anxiety disorders, psychotic disorders, dementia, Parkinson’s disease, stroke, brain tumours).
  • S stands for sleep disorder (apnea, restless legs syndrome, periodic limb movements associated with sleep)
  • O stands for overconcern about falling asleep
  • M stands for medications (steroids, SSRIs antidepressants, theophylline, etc)
  • N stands for noisy or unpleasant environment (extreme heat or cold, sleeping next to a snoring partner)
  • I for idiopathic causes
  • A for anxiety and overactive mind
  • C for circadian rhythm disruption (jet lag, job shift changes, high altitudes)

With regard to evaluation, a medical doctor will start by asking questions about your medical history and sleep patterns. The doctor will need to know the medical history and whether you are taking any medications, including over-the-counter drugs. He/she will also want to know whether anything else has happened in your life, such as any event that is causing stress or trauma. The physician may give you a written test to analyse your mental and emotional well being. A physical exam may be conducted to look for possible underlying conditions. The doctor might screen for psychiatric disorders and drug and alcohol use.

For a diagnosis of insomnia, the disturbed sleep should have lasted for more than 1 month. It should also negatively impact your wellbeing, either through the causing of distress or disturbing mood or performance.

You may be asked to keep a sleep diary to help understand your sleeping patterns. Sometimes even before the first appointment, the doctor will ask you to keep a sleep diary for two weeks. By recording when you go to sleep and when you wake up, along with how long you were awake during the night, a sleep diary will help your sleep medicine physician see your habits. This may give your physician clues about what is causing your insomnia and what course of treatment to take.

Other tests may include a polysomnography (PSG). This is an overnight sleeping test that records sleep patterns. You will not need an overnight sleep study unless the doctor suspects you have sleep apnea or another sleep disorder.

In addition, actigraphy may be conducted. This uses a small, wrist-worn device called an actigraph to measure movement and sleep-wake patterns.

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