Polysomnography (PSG)

Which signals are recorded?

Sensors record brain activity, eye movements, and muscle activity. Other measurements commonly include airflow, breathing effort, heart rate or electrical heart activity, and oxygen saturation. Leg movements and sometimes video may also be included.

The setup depends on the reason for the study. The sleep center selects the relevant signals and provides instructions for your test. The sensors record activity; they do not treat a sleep problem.

Sources: NHLBI: Sleep Studies · MedlinePlus: Sleep Study

Why measure sleep and breathing together?

Recording sleep itself helps the team identify when you are asleep, which sleep stages occur, and how breathing and other events vary across the night. This provides information that a simpler breathing test may not supply.

For example, a report may distinguish an interval of wakefulness from an interval of sleep even if you lay still during both. Quietness and low movement do not necessarily establish that someone was asleep.

Sources: NHLBI: Sleep Studies

Is PSG used only for sleep apnea?

No. Polysomnography can help evaluate several sleep-related concerns. Breathing disorders are one reason; unusual movements or events during sleep may be others. Some evaluations combine an overnight study with separate daytime tests.

Ask what your PSG is intended to clarify. Its name describes a way of collecting information, not a conclusion reached before the recording begins. Not everyone with a sleep complaint needs the same combination of tests.

Sources: NHLBI: Sleep Studies · MedlinePlus: Sleep Study

What should be explained afterward?

The result needs to be interpreted in light of the reason for referral and your symptoms. A technical list of signals and sleep stages is not a follow-up plan. Ask which findings matter, what remains uncertain, and what is recommended next.

If the night was unusual, tell the clinician reviewing the study. They can assess the significance. You do not need to interpret the complete report yourself before your appointment.

Sources: MedlinePlus: Sleep Study

Questions before the study

• Where will this study take place, and is it an attended overnight test?
• What instructions apply to sleep, hair products, food, and my regular medications?
• Should I bring any prescribed sleep equipment?
• Who explains the result, and when will follow-up be arranged?