For diagnosing sleep disorders an accurate history is very essential. A detailed history of a person’s sleeping habits, recorded in a sleep diary, will give a clearer picture of a person’s sleeping patterns and helps to diagnose sleep disorders like insomnia, parasomnias, hypersomnias and circadian rhythm sleep disorders.
A sleep diary is maintained for two weeks and a record is made of a person’s sleeping habits, which includes the time of going to sleep, the time of awakening and the time in between when he was awake. A family member can give additional information regarding certain habits like snoring or sleepwalking.
The following are some of the diagnostic methods employed to evaluate sleep efficiency in a person suffering from sleep disorders:
Epworth sleepiness scale is a self assessment tool, in which a questionnaire is filled out by the person and it estimates the likelihood of falling asleep in different situations. This permits a standardized subjective assessment of daytime sleepiness.
Polysomnogram is an overnight sleep study conducted at a sleep laboratory. It involves multiple tests that are conducted simultaneously on a person. The Sleep laboratory has facilities for the patient to stay overnight. The following steps are recommended before a sleep study:
Avoid napping on the day of the study.
Avoid coffee or tea after 10 AM on the day of appointment.
Stay away from stimulants, alcohol, or sedatives. Most sleep centers request to continue regular medications.
Shower or wash hair on the day of appointment so that it becomes easier to place the electrodes.
Avoid using any hair products, skin lotions or powder.
Eat a normal evening meal before arrival at the sleep lab.
Bring nightclothes or wear the hospital gown.
Bring you own pillow or other items which will make you comfortable
Typically, the patient will be asked to come to the sleep laboratory an hour or two before the patient’s usual bedtime. The electrodes are placed at the appropriate place to enable recording of different parameters.
- A test to study the electrical activity of the brain entails the positioning of electrodes which ensures the electrical activity in the brain. while the patient is asleep. The EEG gives the specialist the exact picture of the stages of sleep, its extent, and arousal rates.
- A study for eye movements during sleep. Electrodes are taped to the skin near the outer edges of the eyes to record the data for an electrocculogram. This helps the examiner to score rapid eye movement sleep (REM).
- A device is placed near the patient's nose and mouth to measure airflow. The airflow ceases when there is an obstruction to airflow and this helps to score apneas and hypopnea.
- A test to study the electrical activity of the muscles of the body. Electrodes are taped or pasted on the patient's chin to detect activity in the jaw muscles. The EMG helps to score the presence of REM sleep, because in this stage of sleep there is skeletal muscle atonia which makes the jaw muscles to relax.
Chest and abdominal movement
- Special belts are placed around the patient's chest and abdomen to detect and record the rising and falling movements associated with the respiration. This helps to score apneas and hypopneas in sleep.
Blood oxygen levels
- A pulse oximeter is a non-invasive device for measuring oxygen content in the blood and is attached to the finger. The blood oxygen levels are lowered when there is airway obstruction as in the case of obstructive sleep apnea.
- A test to study the electrical activity of the heart. Electrodes are attached to the chest to measure heart rate.
- Electrodes are pasted to the lower legs to measure leg movements, which may indicate the presence of periodic limb movement disorder.
Analyzing the test results
- After obtaining these variables a sleep specialist will study them. First the stages of sleep are scored based on the EEG. Following this the various events related to sleep like stoppage of breathing, abnormal movements of the hands and legs and arousals (waking from sleep) are all documented. With the help of the results the sleep specialist can diagnose obstructive sleep apnea and periodic limb movement disorder. Polysomnogram also helps in the diagnosis of other sleep disorders like insomnia, bruxism and narcolepsy.
Multiple Sleep Latency Test (MSLT)
- The parameters employed for Polysomnography are used in this test too and this test is carried out for 20 mins every two hours during the day. This test measures the individual’s ability to fall asleep when conditions are favorable for sleep .
Multiple Wake Test(MWT)
- This test measures a person’s ability to remain awake and helps to assess the effectiveness of stimulant medications used.