0583 Associations Among Daytime Sleepiness, Obesity and AHI In Patients With Obstructive Sleep Apnea

There are strong relationships among daytime sleepiness, obesity and obstructive sleep apnea (OSA) severity. Among OSA patients, some studies suggested that there are strong relationships between obesity and daytime sleepiness, not between OSA severity and daytime sleepiness; though few studies supported the latter relationship. In all those studies, daytime sleepiness was evaluated by Epworth Sleepiness Scale (ESS) alone, not by multiple sleep latency test (MSLT). We explored those relationships utilizing ESS and MSLT simultaneously in OSA patients. A total of 1587 patients with apnea-hypopnea index (AHI) ≥ 5/h were included in this study (85.7% males, mean age = 44.46 ± 11.18 years). All patients underwent ESS and an overnight polysomnography (PSG) followed by MSLT. The ESS and MSLT values were classified into 2 categories based on the cutoff points of 10 score and 5 minutes, respectively. Obesity OSA patients (BMI≥28kg/m2, n=565) had decreases in N2%, N3% and rapid eye movement (REM) sleep% and increases in AHI, total sleep time (TST) and N1% compared with those in non-obesity OSA patients (n=1022). A logistical regression analysis revealed that obesity was associated with subjective sleepiness (ESS score>10) (OR=1.337; 95%CI=1.054 to 1.695), but not objective sleepiness (MSLT score<5min) (OR=1.073; 95%CI=0.816 to 1.412); AHI was associated with objective sleepiness (OR=1.013; 95%CI=1.006 to 1.021), but not subjective sleepiness (OR=1.001; 95%CI=0.994 to 1.007) after adjustment for sex, age, TST, N3%, microarousal index, tobacco use, alcohol drinking, coffee use, hypertension, diabetes and T90%. A multiple linear regression analysis also revealed that obesity (β=0.094, P=0.001), but not AHI (β=0.023, P=0.555) was associated with ESS score; in contrast, AHI (β=-0.121, P=0.002), but not obesity (β=-0.006, P=0.836) was associated with MSLT score. Obesity is associated subjective daytime sleepiness, while OSA severity is associated with objective daytime sleepiness in OSA patients. The results reflect the complexities of physiological mechanisms underlying the associations among daytime sleepiness, obesity and OSA severity. This work was supported by the National Basic Research Program of China (2015CB856406) and National Natural Science Foundation of China (81530002, 81629002).