Sleep deprivation worsens obstructive sleep apnea. Comparison between diurnal and nocturnal polysomnography

Daytime polysomnography (DPG) has been suggested for diagnosis of obstructive sleep apnea syndrome (OSAS), because it is less expensive than whole-night polysomnography investigation (NPG). To ensure sleep during day recordings, patients are often instructed to stay awake the night preceding DPG. This procedure has been validated against NPG, and also against apnea mattress recordings combined with ear oximetry (AMO). Twenty patients with OSAS symptoms were examined with NPG and simultaneous AMO and 2 to 3 weeks later with DPG 3 to 4 h in the morning after 1 nights sleep deprivation. Median apnea-hypopnea index (AHI) of DPG was 37 (95% confidence interval [CI], 19 to 44), significantly higher than median AHI of NPG (14; 95% CI, 12 to 27), whereas median nocturnal oxygen desaturation index (ODI) (11; 95% CI, 9 to 25) did not differ significantly from median AHI of NPG. Sensitivity values for DPG increased from 81 to 100% when the criteria AHI greater than 5, greater than 10, greater than 15, and greater than 20 were used, respectively. Specificity values also increased with the AHI used as cutoff point, from 50% (AHI>5) to 75% (AHI>20). In AMO, there were one false-negative case and four nonclassifiable borderline cases. If these types of simplified tests for OSAS are used for diagnosis, the risk of both false-negative and positive results (DPG) or nonclassifiable borderline cases (AMO) must be considered. Since there was a significant increase in AHI in DPG after sleep deprivation in comparison to conventional NPG, the former procedure should not be used for staging of the disease. These results also stress the importance of advice to OSAS patients concerning regular sleeping habits.