The use of a sleeping pill before a sleep study, known as polysomnography (PSG), is a common concern for patients seeking a diagnosis for a sleep disorder. PSG is a detailed diagnostic tool that measures various physiological parameters during sleep. Because sleep aids chemically alter the sleep state, their presence during the test significantly compromises the accuracy of the results, making medication use a major factor in obtaining a valid diagnosis.
Understanding the Goals of a Sleep Study
The central purpose of polysomnography is to capture a patient’s natural, untreated sleep patterns to identify underlying primary sleep disorders. The test records multiple variables simultaneously, including brain waves (EEG), heart rhythm (EKG), muscle activity, and breathing parameters. The sleep architecture, which is the pattern and duration of the different sleep cycles, is a primary focus of the analysis. For the results to be meaningful, they must reflect the patient’s typical physiology and sleep structure without external chemical interference. Distortion of the sleep architecture by medication can obscure the true severity of a disorder or lead to an incorrect diagnosis.
How Medications Alter Sleep Architecture
Common sleep medications, such as benzodiazepines and Z-drugs, exert specific effects on the brain that directly change the measured sleep profile. These hypnotics typically work by enhancing the activity of the inhibitory neurotransmitter GABA, resulting in measurable alterations. One immediate effect is a decrease in sleep latency (the time it takes to fall asleep) and an increase in the total time spent asleep. However, the quality of the sleep is fundamentally changed, not merely improved.
These medications are known to suppress Rapid Eye Movement (REM) sleep, the stage associated with dreaming, and reduce Slow-Wave Sleep (SWS), often referred to as deep sleep. This suppression of SWS and REM sleep can make the sleep appear less restorative. Furthermore, these drugs often increase the amount of lighter sleep, specifically stage N2 sleep. They can also introduce fast EEG activity, known as beta activity, into the brain wave recordings. This beta activity is a drug-induced artifact that can complicate the reading of the EEG and potentially be misinterpreted by the scoring clinician.
Standard Protocols for Medication Before Testing
To ensure the PSG accurately reflects the patient’s condition, sleep clinics follow standardized instructions regarding medication use. The general recommendation for diagnostic studies is to discontinue all medications with alerting, sedating, or REM-sleep-modulating properties for a designated washout period. This period is necessary to allow the drug and its active metabolites to fully clear from the body’s system.
For many prescription sleep aids, a two-week washout period is generally recommended to minimize interference with sleep architecture. Medications with long half-lives, such as certain antidepressants, may require an even longer washout, potentially extending up to six weeks. Over-the-counter sleep aids and alcohol should also be avoided, typically for at least one week prior to the study.
The patient must consult with the prescribing physician and the sleep clinic before stopping any medication, as abruptly discontinuing some drugs can pose a safety risk. In some cases, a provider may instruct the patient to continue a medication if the goal is to assess the disorder under the patient’s usual, chemically-influenced conditions. Failure to adhere to the specified pre-test protocol often necessitates rescheduling the study to ensure a valid baseline reading.
Clinical Interpretation of Contaminated Results
When a patient takes a sleep aid before a diagnostic study, the resulting data is considered contaminated, requiring the clinician to interpret the findings with caution. The medication effect can obscure the diagnosis of a primary sleep disorder. For example, the drug might mask the severity of insomnia or, conversely, its respiratory depressant effects might overstate the severity of sleep apnea. The presence of drug-induced beta activity in the EEG also complicates the technologist’s ability to accurately score the sleep stages.
The clinical report will often include a note identifying “drug-induced alterations” to the sleep architecture, signaling that the results do not represent the patient’s baseline state. If the medication has significantly altered the physiological recordings, the results may be deemed non-diagnostic or unreliable. In such instances, the sleep physician will recommend a second, medication-free study to establish a true physiological baseline for creating an effective treatment plan.