A sleep study, also known as polysomnography (PSG), is a diagnostic test that records various bodily functions while you sleep to help identify sleep disorders. The overall time commitment for a sleep study can vary. Understanding the typical duration and factors that might alter it can help prepare you for the process.
The Standard Overnight Sleep Study
The most common sleep study is an overnight polysomnography, which generally takes about 8 to 10 hours. Patients typically arrive at a sleep clinic in the evening, usually between 8 p.m. and 10:30 p.m., and depart the following morning, often between 5:30 a.m. and 8 a.m. This timeframe allows for sufficient sleep monitoring.
During this period, a sleep technician attaches various sensors to your head, face, chest, and limbs. This setup takes approximately 40 to 60 minutes. These sensors track brain waves (EEG), eye movements (EOG), muscle activity (EMG), heart rate (ECG), breathing patterns, blood oxygen levels, and body position throughout the night. At least six to seven hours of recorded sleep are typically obtained for accurate data analysis, though a diagnosis can sometimes be made with as little as two hours of sleep data.
Factors Influencing Study Length
Several elements can affect the total duration of a sleep study. One variation is a “split-night” study, which combines a diagnostic assessment with the initiation of continuous positive airway pressure (CPAP) therapy within the same night. If the initial diagnostic portion, lasting at least two hours, indicates severe obstructive sleep apnea (OSA), the patient may be woken up to begin CPAP titration for the remainder of the night. This approach can potentially eliminate the need for a second separate study night.
A sleep study might extend to additional nights if initial results are inconclusive or more data is required for a precise diagnosis. Technical issues with equipment or a patient’s difficulty falling asleep can also necessitate longer monitoring or rescheduling. Home sleep apnea tests (HSATs) offer an alternative, where equipment is used in the patient’s own bed over one or more nights without a technician present, typically requiring at least six to eight hours of recording time for sufficient data collection.
Specialized Sleep Studies and Their Timelines
Beyond the standard overnight PSG, specialized sleep studies address specific conditions and have different durations. The Multiple Sleep Latency Test (MSLT) is usually conducted the day immediately following an overnight PSG to assess excessive daytime sleepiness and diagnose conditions like narcolepsy. This test involves four or five scheduled nap opportunities, each lasting 20 minutes, spaced two hours apart throughout the day. The entire MSLT typically spans about 7 to 8 hours, measuring how quickly a person falls asleep during these naps and if they enter REM sleep.
Another specialized test is the Maintenance of Wakefulness Test (MWT), which often follows an overnight PSG and measures a person’s ability to stay awake in a quiet environment. The MWT usually consists of four trials, each lasting 40 minutes, with two-hour breaks in between. Patients are instructed to remain awake and alert during these trials. This full-day test, similar in length to an MSLT, evaluates a person’s ability to maintain wakefulness, which is particularly relevant for individuals in professions requiring sustained alertness.