Sleep fragmentation: comparison of two definitions of short arousals during sleep in OSAS patients

The measurement of arousals during sleep is useful to quantify sleep fragme ntation. The criteria for electroencephalography (EEG) arousals defined by the American Sleep Disorders Association (ASDA) have recently been criticiz ed because of lack of interobserver agreement. The authors have adopted a s coring method that associates the increase in chin electromyography (EMC) w ith the occurrence of an alpha -rhythm in all sleep stages (Universite Cath olique de Louvain (UCL) definition of arousals). The aim of the present stu dy was to compare the two scoring definitions in terms of agreement and rep eatability and the time taken for scoring in patients with obstructive slee p apnoea syndrome (OSAS) of varying severity. Two readers using both ASDA and UCL definitions scored twenty polysomnograp hies (PSGs) each on two occasions. The PSCs were chosen retrospectively to represent a wide range of arousal index (from 6-82) in OSAS patients. There was no difference in the arousal indices between readers and between scoring methods, The mean+/-SD difference between the two definitions (the bias) was 1.1+/-3.76 (95% confidence interval: -0.66-2.86). There was a str ong linear relationship between the arousal index scored with the two defin itions (r=0.981, p<0.001). Mean+/-SD scoring duration was significantly sho rter for UCL than for ASDA definitions (18.5+/-5.4 versus 25.3+/-6.6 min, p <0.001). In conclusion, it has been found that in obstructive sleep apnoea syndrome patients, the American Sleep Disorders Association and Universite Catholiqu e de Louvain definitions were comparable in terms of agreement and repeatab ility.