Reliability of the Samsung Galaxy for the Detection of Moderate to Severe Obstructive Sleep Apnea

Inclusion Criteria:

* 22 years of age or older
* High pre-test likelihood of moderate to severe obstructive sleep apnea (OSA) based on screening questionnaires (STOP-Bang and Epworth Sleepiness Scale); or prior diagnosis of moderate-severe OSA.
* Able to provide informed consent confirmation

Exclusion Criteria:

* Severe and/or other acute medical illnesses as determined by the Investigator, in particular: Cardiac conditions such as Congestive Heart Failure (CHF), atrial fibrillation, Hx of Movement disorders: Parkinson's, Tremor, Lung conditions: Chronic Obstructive Pulmonary Disease (COPD), chronic bronchitis, emphysema, pulmonary fibrosis, acute episode of flu, allergies, asthma.
* Active comorbid sleep disorders, such as severe insomnia, restless legs syndrome, Periodic Leg Movement During Sleep (PLMS), narcolepsy, idiopathic hypersomnia
* Severe and/or unstable psychiatric disorders such as mood, anxiety, or psychotic disorders
* Individual has a condition the Investigator believes would interfere with his or her ability to provide informed consent, comply with the study protocol, which might confound the interpretation of the study results or put the person at undue risk
* Inability to use a Samsung Galaxy device for sleep tracking
* Inability to have two nights in the Stanford sleep lab.
* Participants who are pregnant
* Tattoos or scars covering the forearm area of both hands