📄 medicine

The impact of acetaminophen on reducing the incidence of postoperative delirium in elderly patients with sepsis in the ICU: A retrospective study and Mendelian randomization analysis

This study combines retrospective analysis of MIMIC-IV data and Mendelian randomization to demonstrate that acetaminophen use is associated with a reduced incidence of postoperative delirium and improved survival outcomes in elderly septic ICU patients, although a direct causal relationship was not confirmed by genetic analysis.

Original authors: Peng Liu, Jiandong Sun, Wenjing Dong, Xiaoxue Ren, Xu Song, Zhiming Zhang, Changsong Wang, zhaodi Zhang

Published 2026-08-03

📖 5 min read🧠 Deep dive

CC BY 4.0

Original authors: Peng Liu, Jiandong Sun, Wenjing Dong, Xiaoxue Ren, Xu Song, Zhiming Zhang, Changsong Wang, zhaodi Zhang

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine the human body as a bustling city. When a severe infection strikes, it's like a massive, chaotic riot breaking out in the streets. This is sepsis, a condition where the body's immune system overreacts to an infection, causing widespread inflammation that can damage its own organs. This is especially dangerous for the city's elderly residents, whose defenses are already a bit worn down.

Now, picture the city's control center: the brain. During a sepsis riot, the brain often gets confused, overwhelmed, and starts acting erratically. This state is called delirium. It's like the city's traffic lights are flashing randomly, causing confusion, memory lapses, and a loss of focus. In the Intensive Care Unit (ICU), where patients are hooked up to machines and surrounded by beeping alarms, this confusion is very common and can make recovery much harder. Doctors have been searching for a simple, safe way to calm the brain down and stop the confusion without causing other problems. One common tool in the medical toolbox is acetaminophen (the active ingredient in Tylenol), usually known for treating headaches and fevers. But could this everyday medicine also act as a peacekeeper for the brain during a sepsis crisis? That's the big question researchers wanted to answer.

The Great ICU Detective Story: Does Acetaminophen Calm the Confusion?

A team of researchers decided to play detective, digging through a massive digital library of medical records called MIMIC-IV. They looked at over 10,000 elderly patients who had been admitted to the ICU with sepsis. They wanted to see if the patients who happened to receive acetaminophen fared better than those who didn't. Think of it like checking two groups of hikers who got lost in a storm: one group had a warm, comforting fire (acetaminophen), and the other didn't. Did the fire help them stay on the right path?

The Good News: Less Confusion and Longer Lives
The investigation revealed some very promising clues. The elderly patients who received acetaminophen were significantly less likely to develop delirium. In fact, the odds of getting confused dropped by about 11% for those who took the drug. It wasn't just about avoiding the "brain fog," either. The patients who got acetaminophen also lived longer. Their chances of surviving 28 days, 90 days, and even a full year were much higher than the patients who didn't get the drug. They also spent less time in the hospital, suggesting they bounced back faster.

The researchers did some extra math to figure out why this happened. They found that part of the reason these patients survived longer was simply because they were less likely to get delirious. It turns out that avoiding the brain confusion was a key link in the chain that led to better survival rates. About 9% of the improvement in hospital survival and 13% of the improvement in ICU survival could be directly traced back to the drug's ability to prevent delirium.

The "Genetic Time Machine" Check
But wait, could it be that the doctors just gave acetaminophen to the patients who were already doing better? To be sure, the researchers used a clever trick called Mendelian Randomization. Imagine this as a "genetic time machine" that looks at people's DNA to see if their natural genetic makeup for needing acetaminophen is linked to their risk of delirium.

Here, the story got a little twisty. The genetic time machine did not find a direct, one-way causal link proving that acetaminophen causes less delirium. However, it did find something interesting in reverse: people who are genetically prone to having delirium seem to use acetaminophen less. This suggests the relationship is complex and might be influenced by how doctors decide to treat patients based on their condition. So, while the real-world data from the ICU shows a strong helpful connection, the genetic data reminds us that we cannot yet say for certain that the drug is the direct cause. The researchers emphasize that future randomized controlled trials are needed to confirm these findings and prove the drug's efficacy.

Who Benefits the Most?
The researchers also looked at different groups of people to see if the "magic fire" worked better for some than others. They found that the drug seemed to work especially well for men, for people who were married, and most notably, for patients who were on mechanical ventilators (breathing machines). For those on ventilators, the protective effect against delirium was incredibly strong. It's as if the drug was a super-charged shield for the most critically ill patients.

The Bottom Line
So, what's the verdict? The study suggests that giving acetaminophen to elderly sepsis patients in the ICU is associated with a lower risk of confusion and better survival rates, making it a promising candidate for further study. It appears to act like a gentle hand on the brain in these real-world observations, reducing the risk of confusion and helping patients survive longer and leave the hospital sooner. However, because the genetic study did not confirm a direct cause-and-effect, this common, everyday drug is not yet a proven "secret weapon" but rather a strong lead that warrants more rigorous testing. The researchers are now calling for more studies to confirm these findings and figure out the perfect way to use this tool for everyone.

Technical Summary: Acetaminophen and Postoperative Delirium in Elderly Sepsis Patients

Problem Statement
Sepsis remains a critical challenge in the Intensive Care Unit (ICU), particularly among elderly patients, characterized by high morbidity, mortality, and complex pathological features. A significant complication in this population is postoperative delirium, an acute brain dysfunction affecting 20% to 80% of critically ill sepsis patients. Delirium exacerbates neurocognitive burdens, prolongs hospital stays, increases mortality risk, and consumes substantial healthcare resources. While current sepsis management relies heavily on anti-infective and supportive care, effective pharmacological interventions for preventing or treating delirium remain elusive. Existing literature suggests that pain management and inflammatory responses are key factors in delirium onset, yet the specific role of widely used analgesics like acetaminophen (paracetamol) in reducing delirium incidence and improving survival in elderly sepsis patients has not been systematically evaluated using robust causal inference methods.

Methodology
This study employed a dual-methodological approach combining retrospective clinical data analysis with bidirectional Mendelian randomization (MR) to investigate the association between acetaminophen use and delirium outcomes.

Retrospective Cohort Analysis:
- Data Source: The study utilized the Medical Information Mart for Intensive Care IV (MIMIC-IV) database (version 3.1), covering ICU admissions from 2008 to 2022.
- Population: From an initial pool of 16,335 elderly patients (≥65 years) with sepsis (defined by Sepsis-3 criteria: SOFA score ≥2 with confirmed/suspected infection), 10,587 patients were included after excluding those without delirium assessments, pre-existing delirium, or missing variables.
- Exposure: Acetaminophen use was defined as administration from ICU admission until the first delirium assessment.
- Outcomes: The primary outcome was the incidence of delirium (diagnosed via CAM-ICU and nursing records). Secondary outcomes included 28-day, 90-day, and 365-day mortality, in-hospital/ICU mortality, and length of stay.
- Statistical Analysis: Multivariable logistic regression was used to assess the association between acetaminophen and delirium, adjusting for 50 covariates (demographics, vital signs, labs, comorbidities, and interventions). Sensitivity analyses included Propensity Score Matching (PSM) to balance baseline differences, and subgroup analyses across various clinical and demographic strata. Mediation analysis was conducted to quantify the extent to which delirium mediates the relationship between acetaminophen and mortality.
Mendelian Randomization (MR) Analysis:
- Design: A bidirectional two-sample MR analysis was performed to explore potential causal relationships and minimize confounding.
- Data Sources: GWAS summary statistics for delirium were sourced from the FinnGen R12 database, while acetaminophen data came from the DMRdb database.
- Methods: Instrumental variables (IVs) were selected with strict thresholds ( $r^2 < 0.001$ , $P < 5 \times 10^{-8}$ ). Analyses utilized Inverse Variance Weighted (IVW), Weighted Median, and MR-Egger regression methods to assess causality, pleiotropy, and heterogeneity.

Key Results

Baseline Characteristics: Among the 10,587 patients, 2,952 (27.9%) received acetaminophen. The acetaminophen group exhibited slightly younger age, higher male and married proportions, and generally lower comorbidity burdens (e.g., lower rates of diabetes, heart failure, and renal disease) compared to the non-exposed group.
Association with Delirium: In the fully adjusted logistic regression model (Model 3), acetaminophen use was significantly associated with a reduced risk of delirium (OR = 0.8935, 95% CI: 0.8005–0.9973, $P = 0.0445$ ). However, in the propensity score-matched (PSM) sensitivity analysis, this association weakened and became non-significant (OR = 0.9639, $P = 0.5938$ ).
Mortality and Length of Stay: Acetaminophen use was significantly associated with reduced mortality at all time points (28-day, 90-day, and 365-day) and reduced in-hospital and ICU mortality ( $P < 0.001$ for all). Patients using acetaminophen also had significantly shorter hospital lengths of stay ( $P < 0.001$ ), though no significant difference was found in ICU length of stay.
Mediation Analysis: Delirium was found to partially mediate the effect of acetaminophen on mortality. Specifically, delirium accounted for 9% of the mediating effect on in-hospital mortality and 13% on ICU mortality.
Subgroup Analysis: The protective association against delirium was consistent across most subgroups but was notably stronger in male patients, married patients, and those receiving mechanical ventilation.
Mendelian Randomization Findings: The bidirectional MR analysis did not identify a significant direct causal relationship between acetaminophen use and delirium risk (Forward MR: OR = 1.02, $P = 0.895$ ). Conversely, reverse MR suggested that genetically predicted higher risk of delirium was negatively correlated with acetaminophen usage, implying a potential reverse causation or behavioral adaptation where patients at higher risk receive less of the drug.

Significance and Claims
The authors claim that this study provides the first systematic investigation combining retrospective clinical data and genetic epidemiological methods to evaluate acetaminophen's impact on delirium in elderly sepsis patients. The findings suggest that acetaminophen use is associated with improved clinical outcomes, including lower delirium incidence and reduced mortality, potentially through mechanisms involving the inhibition of central prostaglandin synthesis and reduction of neuroinflammation.

The study emphasizes the clinical translational potential of acetaminophen as a safe, non-opioid analgesic that may reduce dependence on sedatives (like midazolam) and mitigate the neurotoxic effects of inflammation. The authors posit that these results offer real-world evidence supporting the optimization of pain management strategies in the ICU to prevent delirium. However, the paper modestly acknowledges limitations, including the retrospective nature of the data, potential residual confounding, and the lack of specific dosage analysis. Consequently, the authors conclude that while the findings are promising, future prospective randomized controlled trials are necessary to validate these associations and elucidate the precise mechanisms before definitive clinical guidelines can be established.

The Great ICU Detective Story: Does Acetaminophen Calm the Confusion?

Technical Summary: Acetaminophen and Postoperative Delirium in Elderly Sepsis Patients

More like this