Sleeping Pill Fails to Lengthen Daytime Sleep for Night Shift Workers in Rigorous Trial

For the millions of nurses, security guards, factory operators, and emergency dispatchers who work through the night, the struggle to sleep during the day is not a minor inconvenience. It is a chronic, biologically rooted problem that erodes health, safety, and quality of life. Now, a carefully designed randomized controlled trial led by researchers at the University of California, San Francisco, and published in the Journal of Clinical Sleep Medicine, has tested one of the most promising new classes of sleep medications against that problem, and the results are a sobering reality check. The drug, lemborexant, belongs to a family of medicines known as dual orexin receptor antagonists, or DORAs, which work by a mechanism fundamentally different from the sedatives of previous generations. Rather than broadly dampening brain activity, DORAs selectively block the signaling of hypocretin and orexin, two neuropeptides that act as chemical switches for wakefulness. Because the circadian clock itself drives orexin-mediated arousal during the biological day, precisely when night shift workers are trying to sleep, the idea that blocking this system could help them rest has captivated sleep researchers for years.

The rationale behind the trial is grounded in a deep biological dilemma. Human sleep is governed by two interacting processes: a homeostatic pressure that builds the longer we stay awake, and a circadian rhythm orchestrated by the suprachiasmatic nucleus of the hypothalamus, which promotes alertness during the daytime hours. Night shift workers face a cruel mismatch. Their behavior demands sleep at a time when their internal biology is shouting wake up. The orexin system sits at the heart of that arousal signal, stabilizing wakefulness and preventing sleep from intruding on the active period. In theory, a drug that quiets orexin signaling could lower the biological barrier to daytime sleep. An earlier trial of suvorexant, another DORA, had suggested the approach held promise, and lemborexant, approved for insomnia treatment, offered a well-characterized candidate with a favorable safety profile. The UCSF team, led by Aric Prather and Andrew Krystal, set out to put the hypothesis to a rigorous test.

The study design reflected the methodological standards expected of modern sleep research. Twenty-nine night shift workers, with a mean age of 37.2 years and predominantly female, completed a two-week baseline period during which their habitual daytime sleep was measured. Participants then entered a one-week titration phase in which they received either 5 milligrams of lemborexant or an identical placebo, followed by a two-week maintenance period in which some participants remained at 5 milligrams, others were titrated up to 10 milligrams, and the rest continued on placebo. The trial was double-blind, meaning neither participants nor investigators knew who received the active drug, and it was registered at ClinicalTrials.gov under identifier NCT05344443. The researchers collected sleep diaries and wrist actigraphy, a motion-sensing technique that provides an objective estimate of sleep timing and duration, allowing them to quantify total daytime sleep duration, sleep efficiency, and subjective sleep quality across the entire study period.

The primary outcome was total daytime sleep duration, and here the verdict was unambiguous. Using linear mixed models, a statistical framework well suited to repeated measurements collected over time within the same individuals, the researchers found no significant difference between the lemborexant group and the placebo group, whether sleep was measured by diary or by actigraphy. The drug did not lengthen the sleep of night shift workers relative to an inert pill. Nor did the secondary outcomes tell a more encouraging story. Sleep efficiency, the proportion of time in bed actually spent asleep, did not improve differentially. Subjective sleep quality, rated by participants themselves, showed no advantage for the active drug. Even insomnia severity, assessed with validated clinical instruments, did not decline more in the lemborexant group than in the placebo group. For a medication class that has transformed the treatment of conventional insomnia, the failure to move the needle in this population is a finding that demands explanation.

Yet buried within the null result was a signal that the investigators considered worth pursuing. In exploratory analyses, participants who had been titrated up to the 10 milligram dose showed a statistically significant improvement in diary-based sleep duration compared with those who remained at 5 milligrams. The difference between the 10 milligram group and placebo, however, did not reach statistical significance, which means the finding must be treated as hypothesis-generating rather than as evidence of efficacy. Still, the pattern is scientifically meaningful. It suggests that the dose of orexin blockade may be a critical variable, and that the 5 milligram starting dose, chosen conservatively for safety in a first trial, may simply have been insufficient to overcome the powerful circadian drive for wakefulness that night shift workers confront when they lie down after a night on the job.

Safety data offered one clear positive. No serious adverse events were reported among participants receiving lemborexant, consistent with the drug’s established tolerability profile in insomnia trials. This matters because the pharmacological options available to shift workers have long been limited and problematic. Older hypnotics, including benzodiazepines and Z-drugs such as zopiclone, carry risks of dependence, cognitive impairment, and residual sedation that can bleed into the evening hours when workers must drive home or return to duty. A Cochrane review of pharmacological interventions for shift work-related sleepiness and sleep disturbance concluded that the evidence base was thin and the benefits uncertain. Against that backdrop, a well-tolerated medication that works through a targeted mechanism would represent genuine progress, which is precisely why the field has invested hope in the DORA class.

The stakes extend far beyond the laboratory. Shift work disorder, characterized by insomnia during the attempted sleep period and excessive sleepiness during waking hours, affects a substantial fraction of the night shift workforce and is associated with elevated risks of cardiovascular disease, metabolic dysfunction, and certain cancers, including breast cancer, according to large systematic reviews. Sleep-deprived workers also face heightened risks of occupational accidents and errors, with consequences that ripple through hospitals, transportation networks, and industrial sites. Because an estimated one in five workers in industrialized countries holds a schedule that falls outside the standard daytime window, even a modest pharmacological improvement in daytime sleep could translate into meaningful public health gains. The current trial does not deliver that improvement, but it does sharpen the questions that future research must answer.

Those questions are numerous. The trial was explicitly a pilot, with only 15 participants receiving lemborexant and 14 receiving placebo, and small samples are known to produce imprecise treatment effect estimates that can obscure real effects or exaggerate spurious ones. The sample was also overwhelmingly female, which may limit generalizability, and the two-week maintenance period may have been too brief to capture the full effect of circadian adaptation combined with pharmacotherapy. The actigraphy measurements, while objective, have known limitations in insomnia populations, where misclassification of quiet wakefulness as sleep can bias duration estimates. And the exploratory dose finding raises the possibility that a trial designed from the outset to test 10 milligrams, or even higher exposure, with a larger and more balanced sample, could yield a different result. The authors themselves call for larger studies that ensure participants receive an adequate dose, a recommendation that the exploratory data make difficult to ignore.

For now, the message for clinicians and the millions of patients they serve is one of tempered expectations. Lemborexant, at the doses tested in this trial, cannot currently be recommended as a treatment for daytime sleep difficulties in night shift workers, and the overall result stands as a reminder that a compelling biological rationale does not guarantee clinical efficacy. But the trial also exemplifies how science advances: a precise hypothesis, a rigorous randomized design, honest reporting of a null result, and a carefully flagged exploratory signal pointing toward the next experiment. The orexin system remains a legitimate and intriguing target for shift work sleep disorder, and the question of whether adequate doses of DORAs can tip the circadian balance toward sleep during the biological day is now clearly framed. Until larger trials answer it, night shift workers seeking better daytime rest will need to rely on the non-pharmacological strategies with stronger evidence, including carefully timed light exposure, consistent sleep scheduling, and behavioral treatments, while researchers continue the search for a medication that can finally align the pharmacy with the body clock.

Subject of Research: A randomized controlled trial of lemborexant for improving daytime sleep in night shift workers

Article Title: Effects of lemborexant vs placebo on total daytime sleep in shift workers: a randomized controlled trial

Article References: Prather, A. A., Mitgang, D., Plaut, T. C., Ovais, T., & Krystal, A. D. (2026). Effects of lemborexant vs placebo on total daytime sleep in shift workers: a randomized controlled trial. Journal of Clinical Sleep Medicine, 22(1), Article 185. https://doi.org/10.1007/s44470-026-00199-0

Image Credits: AI Generated

DOI: 10.1007/s44470-026-00199-0

Keywords: lemborexant, shift work, daytime sleep, orexin, dual orexin receptor antagonists, circadian rhythm, insomnia, randomized controlled trial, actigraphy, sleep medicine, night shift workers, sleep duration