Recent studies presented at the American Thoracic Society (ATS) 2025 International Conference highlight the critical role of sleep patterns in intensive care unit (ICU) patients, suggesting that sleep disturbances may be more than just a comfort issue—they could serve as important biomarkers for patient outcomes and recovery.
Atypical N3 Sleep Patterns Predict Longer ICU Stays
Researchers conducted an observational study evaluating atypical N3 (AN3) sleep—a delta wave pattern with minimal theta and sigma activity—among critically ill patients. Using FDA-approved Sleep Profiler technology to record 24-hour sleep data, the study included 56 patients with sufficient sleep recording time.
The findings revealed that patients with more than 1.5 hours of AN3 sleep (n=25) experienced significantly longer ICU stays compared to those with less AN3 sleep (15.6 vs 7.5 days; P < .001). These patients were also typically older (78.2 vs 60.8 years; P < .001) and had lower Glasgow Coma Scale scores (8.9 vs 12.0; P = .006).
Most notably, AN3 sleep was significantly associated with ICU stays longer than 10 days (OR, 1.33; 95% CI, 1.04-1.71; P = .023), suggesting its potential as a biomarker for prolonged ICU admissions. While AN3 did not correlate with mortality, disposition, sepsis, or intubation status, researchers noted this could be due to the small cohort size.
"Though this current study is limited to a single center, our findings suggest that AN3 may have a clinical role in the early recognition of outcomes in ICU patients, which warrants further investigation," the study authors concluded.
Hypersomnia Associated with Poorer Clinical Outcomes
A complementary study from Mount Sinai focused on hypersomnia, defined as more than 11 hours of sleep in a 24-hour period, and its association with patient outcomes in the ICU.
The research showed that patients with hypersomnia (n=34) had significantly worse clinical indicators than those sleeping less than 11 hours (n=22). Hypersomnic patients were older (74 vs 61.3 years; P = .03), had higher APACHE II scores (20.1 vs 15.1; P = .026), and experienced longer ICU stays (17.4 vs 10.9 days; P = .001) and hospital stays (26.9 vs 17.8 days; P = .004).
Perhaps most concerning, mortality was significantly higher among patients with hypersomnia (50% vs 13.6%; P = .009). These patients were also less likely to be discharged home (14.7% vs 63.2%; P < .001) and had higher rates of sepsis (67.6% vs 36.4%), intubation (70.6% vs 9.1%), and sedation (38.2% vs 0%).
While hypersomnia may not be an independent predictor due to confounding variables like age and illness severity, it shows promise as a marker of poor outcomes and may help identify high-risk patients early in their ICU stay.
Temazepam Shows Modest Benefits for ICU Sleep Duration
The randomized, blinded, placebo-controlled DREAM trial examined the efficacy of temazepam in improving sleep for ICU patients. Conducted in Australia, the study included 26 critically ill patients receiving nightly doses of 10 mg to 30 mg temazepam and 27 receiving placebo.
Patients taking temazepam slept a mean of 351 minutes versus 287 minutes in the placebo group—a 64-minute difference that narrowly missed statistical significance (P = .07). However, in an adjusted multivariable model accounting for sex, age, illness severity, and ICU stay length, the difference increased to 77 minutes and reached significance (P = .04).
Despite this improvement in objective sleep time, subjective sleep quality showed no significant differences between groups, whether assessed by nurses (57 vs 49; P = .15) or patients themselves (50 vs 51; P = .70). These findings suggest temazepam may modestly increase sleep quantity but may not meaningfully improve perceived sleep quality.
Post-ICU Insomnia Common in Acute Respiratory Failure Patients
Additional research presented at ATS 2025 revealed the high prevalence of insomnia among patients admitted to the ICU with acute respiratory failure (ARF).
The study, presented by Dr. Dexter Corlett from Indiana University School of Medicine, analyzed data from 362 patients who completed the Insomnia Severity Index (ISI) at discharge. Among this cohort, 31.2% reported clinical insomnia and 29.6% reported subthreshold insomnia—meaning over 60% experienced some degree of sleep disturbance.
Patients with clinical insomnia had significantly increased rates of anxiety (47%) compared to those with subthreshold insomnia (31%) or no insomnia (25%; P = .001). They also had greater rates of depression (53%) compared to those with subthreshold insomnia (31%) or no insomnia (25%; P = .032).
In a logistic regression model, patients with baseline anxiety had significantly increased odds of developing clinical insomnia (OR, 2.07; 95% CI, 1.17-3.65), as did those with a neurologic etiology of their ARF (OR, 3.12; 95% CI, 1.35-7.22).
"Preexisting mental health diagnoses and a neurologic cause for acute respiratory failure were significant risk factors for post-ICU sleep dysfunction," the investigators concluded. "Further study is needed to help determine interventions to reduce sleep disturbances both during ICU admission and after discharge."
Clinical Implications
These studies collectively highlight the importance of monitoring and addressing sleep disturbances in ICU patients. Abnormal sleep patterns may serve as early warning signs for prolonged ICU stays and poorer outcomes, potentially allowing clinicians to identify high-risk patients earlier in their care journey.
While pharmacologic interventions like temazepam show some promise in extending sleep duration, their impact on subjective sleep quality appears limited. This suggests that comprehensive approaches to improving ICU sleep may need to address multiple factors beyond medication alone.
For patients recovering from acute respiratory failure, the high prevalence of post-ICU insomnia underscores the need for sleep assessment and management as part of discharge planning and follow-up care, particularly for those with pre-existing mental health conditions or neurologic causes of respiratory failure.
As research in this area continues to evolve, sleep monitoring may become an increasingly important component of critical care, offering valuable insights into patient prognosis and recovery potential.
