Mild sleep apnea: An Apnea-Hypopnea Index (AHI) of five to 14 events per hour.

Moderate sleep apnea: An Apnea-Hypopnea Index (AHI) of 15 to 29 events per hour.Severe sleep apnea: An Apnea-Hypopnea Index (AHI) of 30 or more events per hour.

To examine the differences in postural stability, anxiety/depression, and quality of life of the patients according to the severity of Obstructive Sleep Apnea Syndrome.

The 30 Seconds Sit to Stand Test is a method used to measure the lower extremity muscle strength and postural stability.

The Hospital Anxiety and Depression Scale (HADS) is a self-report scale developed to determine the risk levels of patients in terms of anxiety and depression. HADS consists of two subscales, one measuring anxiety, with seven items, and another measuring depression, with seven items, which score separately. Those with a score of 10 and above for the anxiety subscale and those with a score of 7 and above for the depression subscale are defined as high-risk patients.

The Short-form 36 questionaire is used to measure Quality of life assessment of Patients. The 36-Item Short Form (SF-36) is an often used, well-researched, self-reported measure of health. It comprises 36 questions that cover eight domains of health. These; physical function (10 items), social function (2 items), role difficulty due to physical problems (4 items) and emotional problems (3 items), mental health (5 items), vitality (4 items), bodily pain (2 item), general health (5 items).