OBJECTIVE/BACKGROUND: Comorbid insomnia with obstructive sleep apnea (COMISA) is associated with worse daytime function and more medical/psychiatric comorbidities vs either condition alone. COMISA may negatively impact sleep duration and reduce rapid eye movement (REM) sleep, thereby impairing cognition. These post-hoc analyses evaluated the effect of lemborexant (LEM), a dual-orexin-receptor antagonist approved for adults with insomnia, on sleep architecture in participants with COMISA. PATIENTS/METHODS: E2006-G000-304 was a phase 3, one-month polysomnography trial in adults aged ≥55 years with insomnia receiving LEM 5 mg (LEM5) or 10 mg (LEM10), placebo (PBO), or zolpidem-tartrate-extended-release 6.25 mg (ZOL). Sleep architecture was determined from 2 nights during placebo run-in (baseline), nights 1 and 2 (NT1/2), and nights 29 and 30 (NT29/30) of treatment. RESULTS: In the Full Analysis Set, 40.8 % (410/1006) had mild obstructive sleep apnea (OSA
apnea-hypopnea-index ≥5 and <
15 events/hour of sleep). Mean change from baseline (CFB) in total sleep time (TST) was significantly greater at NT1/2 and NT29/30 with LEM5 and LEM10 vs ZOL (NT1/2, LEM5, P ≥ 0.05
LEM10, P <
0.0001
NT29/30, both P <
0.0001) and PBO (NT1/2 and NT29/30, all P <
0.0001). REM sleep and REM latency CFB were significantly greater (P <
0.0001 and P <
0.01, respectively) for LEM5 and LEM10 vs PBO/ZOL at NT1/2 and NT29/30. CONCLUSIONS: LEM significantly increased TST in participants with insomnia and mild OSA. Importantly, REM sleep, associated with cognitive performance, increased. These data support the use of LEM in patients with insomnia and mild OSA. GOV REGISTRATION: NCT02783729.