THE RELATION BETWEEN MULTIPLE SLEEP LATENCY TEST FINDINGS AND THE FREQUENCY OF APNEIC EVENTS IN REM AND NON-REM SLEEP

Study objectives: A recent study of 34 patients with mild obstructive sleep apnea syndrome (OSAS) suggested that the number of apneas and hy popneas per hour of sleep (apnea/hypopnea index [AHI]) may show a stro nger correlation with sleepiness, as measured by the Multiple Sleep La tency Test (MSLT), when calculated for rapid eye movement (REM) sleep alone (AHIR) as opposed to the entire night. We sought to reexamine th is possibility in a larger group of similar patients and in patients w ho had a wider range of OSAS severity. Design: Retrospective and obser vational. Setting: A large, accredited, academic sleep disorders cente r where a database of sleep study results is maintained. Patients: We studied 1,146 persons who had polysomnography and MSLTs for clinical i ndications. Results: In Linear regression models, the AHI explained 11 .0% of the valiance in MSLT results, AHIN (AHI during non-REM sleep) e xplained 10.8%, and AHIR explained only 6.0% (p less than or equal to 0.0001 for each). Among subjects with AHI < 10, the AHI explained 3.1% of the variance (p=0.0012), the AHIN 2.3% (p=0.0049), and the AHIR 0. 2% (p=0.40). Among all subjects, the ratio AHIR/AHIN had no influence on the overall relationship between AHI and sleepiness (p=0.23). Concl usions: We conclude that apneic events during REM and non-REM sleep pr obably contribute equally to sleepiness as measured by the MSLT.