Comparing MSLT and ESS in the measurement of excessive daytime sleepiness in obstructive sleep apnoea syndrome.

Objective: The objective of this study is to compare the use of Multiple Sleep Latency Test (MSLT) and Epworth Sleepiness Scale (ESS) in measuring excessive daytime sleepiness (EDS) in patients with different severity of obstructive sleep apnoea syndrome (OSAS).

Methods: Two hundred ninety-six consecutive OSAS patients, with their EDS measured by a Chinese version of ESS and a five-nap MSLT, and their severity of OSAS (determined by respiratory disturbance index) by a nocturnal polysomnogram, were classified into mild (RDI 5-15/h, n=59), moderate (RDI 15-30/h, n=71) and severe (RDI >30/h, n=166) groups, respectively. Their ESS, MSLT and other sleep parameters were compared.

Results: The severe group had significantly shorter mean sleep latency (MSL=6.26+/-4.90 min) than the moderate (8.26+/-4.57 min) and mild groups had (8.07+/-4.37 min). There was no significant difference in their ESS scores.

Conclusions: MSLT is better than ESS in the measurement of EDS in relation to the severity of OSAS in clinical patients.