Parasomnias and obstructive sleep apnea syndrome: in search for a parasomnia evaluating tool appropriate for OSAS screening

Background
Obstructive sleep apnea syndrome (OSAS) is the most common form of sleep-disordered breathing. It is also a known major risk factor of parasomnias.

Objectives
To verify if an additional diagnostic tool for parasomnia assessment might be useful in OSAS screening. Additionally, to investigate the possible relations of parameters measured during polygraphy evaluation and the severity/frequency of parasomnia episodes in order to find the pathophysiological background of increased frequency of parasomnias in OSAS cases.

Material and methods
Parasomnia evaluation with the Paris Arousal Disorder Severity Scale (PADSS) and OSAS evaluation with polygraphy in a group of 105 adult patients hospitalized for assessment of possible OSAS.

Results
According to the polygraphic evaluation, patients were divided into: non-OSAS (n = 19, 18.1%), mild OSAS (n = 31, 29.52%), moderate OSAS (n = 21, 20%) and severe OSAS (n = 34, 32.38%). Based on the recommended cut-off score of 13 points in PADSS, two groups of patients emerged after the parasomnia evaluation: with positive (n = 10) and negative (n = 95) results. PADSS achieved sensitivity of 10.9% and 92% specificity when used for moderate and severe OSAS screening. The positive predictive value (PPV) reached 60%, negative predictive value (NPV) – 48.4%. A statistically significant elongation of the percentage of estimated sleep time below 80% blood oxygen saturation emerged in patients with positive PADSS scores (p = 0,006). Focusing on the parasomnia frequency criterion did not significantly affect the results.

Conclusions
Due to low sensitivity, PPV and NPV PADSS cannot be used as a screening tool in possible OSAS assessment. Another tool with higher sensitivity should be developed, also including assessment of other parasomnias and sleep-related movement disorders. Cyclic intermittent hypoxia might be the cause of the higher frequency of arousal disorders in OSAS patients.