- Design
- Target-trial emulation in an ICU database
- Population
- 12,922 adult ICU stays of at least 48 hours, delirium-free at entry
- Primary outcome
- Incident delirium
- Effect
- High vs low overnight contacts: adjusted HR 1.43 (95% CI 1.27–1.60)
Using the MIMIC-IV intensive care database, investigators emulated a target trial in 12,922 adult ICU stays of at least 48 hours, all delirium-free at 48 hours. Exposure was the rate of overnight care contacts between 22:00 and 06:00: vital-sign charting, blood draws and medication rounds.
Patients with above-median overnight contacts had a 43% higher hazard of later delirium (adjusted HR 1.43, 95% CI 1.27–1.60). Risk rose with each tertile, and vital-sign charting and phlebotomy carried more risk than medication rounds.
Sicker patients are checked more often, and early delirium can itself prompt more checks, so this cannot prove cause. But many overnight observations and bloods are routine rather than needed, and bundling them is low-risk.
- Review whether hourly overnight observations are still needed for each stable patient.
- Schedule routine blood tests outside 22:00 to 06:00 where clinically safe.
- Cluster overnight care so patients have longer unbroken sleep.
- Continue standard delirium prevention: orientation, mobility, glasses and hearing aids.
Why it matters
Routine overnight care may be part of the delirium problem rather than neutral background.
Don't overread it
This is observational; it does not show that cutting overnight contacts prevents delirium.
The statistics, in plain English
An adjusted hazard ratio of 1.43 means a 43% higher rate of delirium after accounting for measured illness severity. The dose–response pattern strengthens the link, but residual confounding and reverse causation are both plausible.
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