0437 THE CLINICAL UTILITY OF SUBJECTIVE VS. OBJECTIVE TESTS OF EXCESSIVE DAYTIME SLEEPINESS IN THE ASSESSMENT OF PATIENTS WITH SLEEP APNEA

Abstract

Excessive daytime sleepiness (EDS) is highly prevalent in obstructive sleep apnea (OSA). In clinical practice, EDS is assessed subjectively with the Epworth Sleepiness Scale (ESS), whereas Multiple Sleep Latency Test (MSLT) is the standard test for the objective assessment of EDS. Psychomotor vigilance task (PVT) has been suggested as a convenient, simpler method than MSLT to assess EDS. In this study, we examined the association between these three methods and their possible utility as predictors of cardiovascular morbidity by examining their association with preclinical markers of metabolic risk, i.e. the proinflammatory cytokine interleukin-6 (IL-6). We studied 58 OSA patients (53.7 ± 7.0y, 63.8% male) who underwent 8-hour in-lab polysomnography for 4 consecutive nights. Four trials of MSLT and PVT were administered on the 4th day every 2 hours. PVT was performed an hour before MSLT. PVT variables included number of lapses, mean reciprocal of the fastest 10% and slowest 10% reaction times (RTs), and median of 1/RT. ESS was assessed on day 1 of the study. Twenty-four-hour profiles of IL-6 levels were assessed on the 4th day. Lower MSLT values were associated with significantly elevated 24-hour (β=-0.34, p=0.01), daytime (β=-0.30, p=0.02) and nighttime (β=-0.38, p<0.01) IL-6 levels. Higher ESS scores were significantly associated with greater number of lapses (β=0.34, p=0.021) and lower values of slowest 10% (β=-0.30, p=0.04) and 1/RT (β=-0.36, p=0.01) but not with IL-6 levels. No significant associations were found between PVT performance, and IL-6 levels or PVT and MSLT. Our findings suggest that in OSA, MSLT is associated with low-grade inflammation whereas ESS is associated with impaired sustained attention/vigilance as measured by PVT. It appears that MSLT is a good predictor for cardiovascular morbidity whereas ESS predicts impaired performance in OSA patients. R01 HL64415