Importance of psychiatric evaluation and long-term outcomes of delirium in lung transplant recipients

Abstract

Objective

Lung transplantation (LT) is the only definitive treatment for end-stage lung diseases; however, patients often experience psychiatric problems that can affect post-transplant recovery. Although postoperative delirium frequently occurs, its risk factors and influence on mortality are not well established. This study aimed to evaluate the incidence of LT-associated psychiatric issues and analyse the association of delirium with mortality

Design

Retrospective cohort study.

Subjects/patients

Patients who underwent LT between January 2013 and March 2023.

Methods

We reviewed the incidence of psychiatric conditions before and after LT. Logistic regression analysis identified risk factors for postoperative delirium, and survival analysis was conducted.

Results

Pre-transplant psychiatric assessments revealed mild anxiety and depression among 398 patients. Notably, 45% of patients experienced delirium after LT. Patients with a higher body mass index (BMI), longer operation duration and high Beck Anxiety Inventory scores exhibited an increased risk of postoperative delirium. Furthermore, patients who developed postoperative delirium had a higher 2- and 5-year mortality rate.

Conclusions

The findings revealed that pre-transplant anxiety, high BMI and prolonged operative duration increase the risk of postoperative delirium risk, which in turn affects long-term mortality. Comprehensive psychiatric evaluation and targeted management are essential for improving post-transplant outcomes.

Introduction

Psychiatric conditions, specifically anxiety and depression, are common among patients with end-stage lung disease [1–4]. These conditions are often exacerbated by the physical burden of the disease, including chronic dyspnoea, persistent fatigue and impaired sleep quality [5,6]. Psychiatric problems are also common among solid organ transplant candidates [7]; however, research specifically focusing on lung transplantation (LT) candidates remains limited. Although a few studies have examined the association between depression and mortality [8–10], evidence regarding the impact of other mental health problems on long-term mortality remains inconclusive [11].

A prolonged waiting period and critical condition [12,13] can profoundly influence the mental health of patients [14]. Recognizing the importance of psychological well-being for transplant outcomes, the International Society for Heart and Lung Transplantation (ISHLT) recommends a comprehensive pre-listing assessment. This assessment evaluates an individual’s psychological health, social support network and ability to follow complex medical regimens [15].

Patient and surgical factors influence the risk of postoperative delirium. Older age, multiple comorbidities, physical frailty and pre-existing psychiatric conditions could be significant contributors to postoperative delirium [16–18]. Additionally, the duration and complexity of surgery further affect delirium risk [19].

LT candidates face heightened delirium risk because of their preoperative critical condition. Owing to their severe physical deconditioning and dependence on life-sustaining interventions – including supplemental oxygen, mechanical ventilation (MV) and extracorporeal membrane oxygenation (ECMO) – they are vulnerable to postoperative cognitive complications. Furthermore, after LT, most patients are transferred to the intensive care unit (ICU) and require MV support and continuous administration of three categories of immunosuppressive agents, including high-dose steroids, calcineurin inhibitors and antiproliferative agents [20] alongside prophylactic antibiotics. This increased risk warrants thorough preoperative assessment and targeted perioperative management to enhance patient outcomes. Nevertheless, research involving psychiatric evaluation [14,21,22] and delirium [16,23–25] in LT recipients remains markedly limited. Therefore, the aim of this study was to evaluate the incidence of psychiatric conditions before and after LT procedures to identify risk factors for post-LT delirium and assess its impact on long-term outcomes among LT recipients.

Methods

Study population

This retrospective cohort study was conducted at a single centre. Data on patients who underwent LT between January 2013 and March 2023 were retrospectively analysed in July 2024. During the study period, 421 LT procedures were conducted. After excluding 23 patients (individuals aged <18 years (n = 9), foreigners (n = 2), re-transplantation cases (n = 7) and concurrent multi-organ transplantation cases (n = 5)), 398 were included in the final analysis (Figure 1). Foreigners were excluded to avoid potential bias arising from language barriers during in-depth psychiatric interviews and the completion of standardized psychological questionnaire.

Figure 1.

Flowchart of study population.

Data collection

Demographic and clinical data, including age, sex, body mass index (BMI) and pre-existing comorbidities, were obtained from electronic medical records. Psychiatric evaluation data, including psychiatric consultation records, pre- and post-transplant delirium occurrences, and psychiatric medication use, were comprehensively reviewed. Mental health status was assessed using the Beck Depression Inventory (BDI) and Beck Anxiety Inventory (BAI) scores [26,27], along with psychiatric consultation. Notably, the BDI and BAI assessments were performed exclusively during the pre-transplant period as part of the baseline psychological evaluation. Physical functional status was evaluated using the 6-min walk distance (6MWD) test and pulmonary function tests (PFTs).

Perioperative data included the operative date, operation duration, anaesthesia duration and serum ammonia levels on post-operative day 1. Critical care parameters, including ICU admission and discharge dates, MV duration, and ECMO support, were recorded. We examined the incidence of grade-3 primary graft dysfunction (PGD) [28] within 72 hours of surgery, acute kidney injury (AKI) [29] within 48 h up to seven days postoperatively, and acute rejection within 90 days postoperatively to evaluate patient severity immediately following LT. Long-term prognosis was assessed by documenting the incidence of chronic lung allograft dysfunction (CLAD) [30,31] and confirmed mortality during the follow-up period.

Definitions

Delirium was defined as any episode of acute confusion or altered mental status occurring during hospitalization following LT, as confirmed by a psychiatrist. For patients in the ICU who were not sedated after LT, the Intensive Care Delirium Screening Checklist (ICDSC) was used [32], with scores of ≥4 indicating delirium and those of 1–3 indicating subsyndromal delirium. However, only cases formally confirmed by a psychiatrist were classified as delirium events for the purposes of this study. After transfer to the general ward, family caregivers and the attending physician identified suspected cases during ongoing surveillance, which were confirmed by psychiatry. Management was then individualized accordingly.

At our hospital, candidates for LT are routinely admitted for pre-transplant evaluation, including assessment of other organ function and malignancy screening. During this hospitalization, a psychiatrist conducts a mandatory psychiatric interview with all patients, except in cases where the patient’s critical condition precludes such an evaluation.

Pre-transplant psychological status was assessed routinely using standardized questionnaires, excluding patients who were sedated owing to their critical medical condition. BAI scores were categorized as follows: minimal (0–7), mild (8–15), moderate (16–25) and severe (26–63). Similarly, BDI scores were classified as minimal (0–13), mild (14–19), moderate (20–28) and severe (29–63). To ensure a clear baseline assessment, the BAI and BDI were administered exclusively prior to transplantation, while clinical monitoring for new psychiatric symptoms continued throughout the perioperative period. Additionally, a composite psychological distress score was calculated by summing the clinical severity categories of the BAI and BDI (ranging from 0 to 6) to evaluate the cumulative impact of pre-transplant mood symptoms.

Based on the ISHLT diagnostic criteria [30,31], CLAD (particularly bronchiolitis obliterans syndrome) was defined as a substantial and persistent decline (≥20%) in forced expiratory volume in 1 second (FEV₁) from the reference value over a 3-month period. Owing to the formalization of the restrictive allograft syndrome (RAS) definition in 2019, the current criteria could not be fully applied to assess the post-transplant RAS status of patients who were enrolled beginning in 2013.

Statistical analysis

Categorical variables are presented as numbers and percentages, whereas continuous variables are expressed as medians with interquartile ranges. Group comparisons were conducted using the chi-squared test. Logistic regression analysis was conducted to identify risk factors for postoperative delirium. We first conducted univariate logistic regression analyses. The final multivariate model included fixed common covariates (age, sex and BMI) and variables with a univariate p value < 0.1. To address potential non-linear relationships, we explored BMI using quadratic terms (BMI²) and categorical subgroups. However, BMI was ultimately maintained as a continuous variable in the final multivariate models for both delirium and mortality to ensure model stability and parsimony. Operation duration was included as a variable in the logistic analysis rather than anaesthesia duration to account for multicollinearity. For survival analysis, Cox proportional hazards regression was conducted. Covariates were selected if they showed statistical significance in the univariate analysis or based on previously reported risk factors for mortality in patients with LT. To specifically assess the impact of delirium while minimizing confounding, only variables from the pre-transplant and immediate post-transplant periods and those at the time of delirium occurrence were included. No imputation was conducted for missing data. All analyses were conducted using available (non-missing) data. Statistical significance was set at p < 0.05, and all analyses were conducted using R software (version x64 4.4.1; R Foundation for Statistical Computing, Vienna, Austria).

Ethics statement

The study protocol was reviewed and approved by the Institutional Review Board (IRB) of the Severance Hospital Ethics Committee (IRB approval number: 4-2024-0715). The requirement for informed consent was waived by the Severance Hospital IRB due to the retrospective nature of the study. This study was conducted in accordance with the ethical principles of the Declaration of Helsinki.

Results

Study population baseline characteristics

Table 1 shows the baseline characteristics of the study population stratified by post-transplant delirium status. The median age of the cohort was 58 years, with a higher median age of 59 years in the delirium group. The mean BMI was 21.4 kg/m², whereas that of the delirium group was slightly higher (21.9 kg/m²). No significant differences in pre-transplant lung disease, 6MWD or lung function were observed between the groups. Additionally, no significant differences were observed in the main caregivers and marital status of the patients across the groups. However, the postoperative delirium group showed higher pre-transplant BDI scores, and more patients in this group required MV before transplant.

Table 1.

Clinical characteristics of patients based on the occurrence of delirium after lung transplantation.

Characteristics	Postoperative delirium		p Value
	No (N = 219)	Yes (N = 179)
Age, years	56 (46–62)	59 (50–63)	0.030
Sex			0.060
Male	132 (60.3)	125 (69.8)
Female	87 (39.7)	54 (30.2)
BMI (kg/m2)	20.7 (18.4–23.2)	21.9 (18.9–24.6)	0.005
Charlson Comorbidity Index	2 (1.0–3.0)	2 (1.0–3.0)	0.119
Diagnosis before lung transplantation			0.151
COPD	13 (5.9)	7 (3.9)
ILD, including IPF, CTD-ILD and other ILD	159 (72.6)	150 (83.8)
Bronchiectasis	18 (8.2)	7 (3.9)
PPH and Eisenmenger syndrome	7 (3.2)	5 (2.8)
Chronic pulmonary GVHD	21 (9.6)	9 (5.0)
Othersa	1 (0.5)	1 (0.6)
Six minutes walking distance (m)b	240 (130–320)	230 (150–348)	0.517
Pulmonary function testc
FVC (L)	1.7 (1.2–2.1)	1.5 (1.2–2.0)	0.376
FVC (%), predicted	42 (34–52)	41 (33–51)	0.364
FEV1 (L)	1.2 (0.8–1.6)	1.3 (1.0–1.6)	0.138
FVC (%), predicted	42 (29–53)	46 (34–57)	0.091
Main caregiver			0.062
Spouse	140 (63.9)	120 (67.0)
Parents	24 (11.0)	9 (5.0)
Adult children	30 (13.7)	37 (20.7)
Siblings	19 (8.7)	10 (5.6)
Non-family relationships	6 (2.7)	3 (1.7)
Marital status			0.233
Married	189 (86.3)	161 (89.9)
Single	16 (7.3)	6 (3.4)
Divorced	2 (0.9)	4 (2.2)
Unknown	12 (5.5)	8 (4.5)
BAI score	10 (5–19)	12.5 (6–21)	0.061
BDI score	14 (9–18)	15 (10–20.5)	0.048
Pre-transplant respiratory support
Oxygen demand (L/min)			0.245
0–3	74 (33.8)	48 (26.8)
4–6	40 (18.3)	34 (19.0)
>6	3 (1.4)	2 (1.1)
High-flow nasal cannula oxygen	21 (9.6)	11 (6.1)
MV or HMV	81 (37.0)	84 (46.9)
Pre-transplant MV support	74 (33.8)	80 (44.7)	0.034
Duration of pre-transplant MV (days)	14 (8–27)	14 (8–23)	0.734
Pre-transplant ECMO support	59 (26.9)	65 (36.3)	0.057
Duration of ECMO before transplantation (days)	4 (0–15.5)	4.5 (0–15)	0.672
Pre-transplant both MV and ECMO support	52 (23.7)	62 (34.6)	0.023
Pre-transplant ICU admission	84 (38.4)	85 (47.5)	0.083

BMI: body mass index; COPD: chronic obstructive pulmonary disease; ILD: interstitial lung disease; CTD-ILD: connective tissue disease-related interstitial lung disease; PPH: primary pulmonary hypertension; GVHD: graft versus host disease; FVC: forced vital capacity; FEV₁: forced expiratory volume in the first second; BAI: Beck Anxiety Inventory; BDI: Beck Depression Inventory; MV: mechanical ventilation; HMV: home mechanical ventilation: ICU: intensive care unit; MV: mechanical ventilation; ECMO: extracorporeal membrane oxygenation.

Data are presented as numbers (%) or mean (standard deviation).

^a Others include tuberculosis, destroyed lung and post-infectious acute respiratory distress syndrome.

^b Two hundred and sixty-four patients participated in a 6 min walking test.

^c Three hundred and fifteen patients underwent pulmonary function tests.

Post-lung transplant delirium: perioperative characteristics and clinical outcome

The postoperative delirium group had longer operative and anaesthesia durations. This group exhibited higher postoperative ICDSC scores, elevated ammonia levels on postoperative day 1, and longer MV duration post-transplant, with a median of 12 days. There were no significant differences between the two groups in postoperative complications (including bleeding, reoperation or AKI) or in the incidence of PGD and AKI. However, at 1 year after LT, PFT results showed that both forced vital capacity (FVC) and FEV₁ were lower in patients who experienced delirium. In addition, the length of postoperative hospital stay was longer in the delirium group (77 days) compared with those without delirium (58 days), and the proportion of patients discharged within 60 days after LT was lower (40.2%) (Table 2).

Table 2.

Perioperative characteristics and long-term outcomes of patients based on postoperative delirium.

Characteristics	Postoperative delirium		p Value
	No (N = 219)	Yes (N = 179)
Number of transplanted lungs, bilateral	206 (94.1)	174 (97.2)	0.208
Operation duration (hour)	6.2 (5.6–6.8)	6.5 (5.8–7.3)	0.005
Anaesthesia duration (hour)	7.8 (7.1–8.5)	8.1 (7.3–8.8)	0.006
Intensive care delirium screening checklist	2 (1.0–3.0)	3.0 (2.0–4.5)	<0.001
Ammonia level (µg/dL, postoperative day 1)	44 (34–58)	52 (40–65)	0.002
Duration of MV post-transplantation (days)	6 (3–18)	12 (5–32)	<0.001
Use of ECMO post-transplantation	86 (39.3)	81 (45.3)	0.271
Duration of ECMO post-transplantation (days)	2 (1–4)	3 (1–5)	0.875
Post-transplant bleeding	31 (14.2)	28 (15.6)	0.784
Re-operationa	43 (19.6)	40 (22.3)	0.590
Post-transplant acute kidney injury within 2 weeks	39 (17.8)	34 (19.0)	0.862
Primary graft dysfunction within 72 hours, grade 3	86 (39.3)	76 (42.5)	0.588
Acute rejection within 90 days	7 (3.2)	9 (5.0)	0.504
Chronic lung allograft dysfunction	27 (12.3)	27 (15.1)	0.255
Unscheduled re-admission within 3 months	71 (32.4)	63 (35.2)	0.104
In-hospital mortality	31 (14.2)	38 (21.2)	0.085
1-Year mortality	57 (26.0)	56 (31.3)	0.296
2-Year mortality	69 (31.5)	78 (43.6)	0.017
5-Year mortality	86 (39.3)	101 (56.4)	0.001

MV: mechanical ventilation; ECMO: extracorporeal membrane oxygenation.

Data are presented as numbers (%) or mean (standard deviation).

^a Re-operation includes bleeding control, bronchopleural fistula repair and lung resection.

Changes in psychiatric symptoms and medication use before and after LT

The incidence rates of psychiatric symptoms and pharmacological interventions were analysed and compared before and after LT (Table 3). Anxiety and agitation were the most common psychiatric symptoms, with incidence rates of 17.8% pre-LT and 36.2% post-LT. Overall, psychiatric symptom prevalence and medication use increased post-operatively. Delirium typically manifested at a mean of 12.5 days post-operatively. Notably, the proportion of patients diagnosed with delirium increased significantly from 7.8% pre-LT to 45% post-LT.

Table 3.

I­ncidence of psych­­iatric issues and medication use before and after lung transplantation.

Psychiatric issues	Pre-transplantation	Post-transplantation	p Value
Sleep disturbance	39 (9.8)	96 (24.1)	<0.001
Anxiety or agitation	71 (17.8)	144 (36.2)	<0.001
Depressive mood	12 (3.0)	12 (3.0)	1.000
Disorientation, hallucination	4 (1.0)	93 (23.4)	<0.001
Delirium	31 (7.8)	179 (45.0)	<0.001
Medication	Pre-transplantation	Post-transplantation	p Value
Atypical antipsychotics	33 (8.3)	154 (38.7)	<0.001
Typical antipsychotics	6 (1.5)	32 (8.0)	<0.001
Anxiolytics (nonbenzodiazepine)	16 (4.0)	30 (7.5)	0.040
Hypnotics (nonbenzodiazepine)	5 (1.3)	6 (1.5)	1.000
Benzodiazepine	37 (9.3)	40 (10.1)	0.801
Anti-depressant	49 (12.3)	87 (21.9)	<0.001

Data are presented as numbers (%).

Risk factors for post-LT delirium

Logistic regression analysis identified key risk factors associated with post-LT delirium (Table 4). A longer operation duration (adjusted odds ratio (aOR): 1.34, 95% confidence interval (CI): 1.02–1.78), higher pre-transplant BAI scores (aOR: 1.04, 95% CI: 1.00–1.08) and elevated BMI (aOR: 1.14, 95% CI: 1.05–1.23) were associated with an increased risk of post-LT delirium. The composite psychological distress score also showed a significant association with delirium risk (OR 1.19, 95% CI 1.00–1.43, p = 0.049). Pre-transplant psychiatric symptoms, other than delirium, and the use of psychiatric medications were not associated with an increased risk of post-transplant delirium.

Table 4.

Risk factors associated with post-transplant delirium.

Characteristics	Univariate		Multivariate
	OR (95% CI)	p Value	aOR (95% CI)	p Value
Age, years	1.02 (1.00–1.04)	0.022	1.01 (0.97–1.05)	0.607
Sex, male	1.53 (1.01–2.33)	0.048	1.00 (0.51–1.97)	0.993
BMI (kg/m2)	1.08 (1.03–1.14)	0.004	1.14 (1.05–1.23)	0.002
CCI, score	1.15 (0.98–1.35)	0.087	1.11 (0.80–1.53)	0.546
Six minutes walking distance (m)	1.00 (0.99–1.00)	0.447
Pre-transplant MV and ECMO support	1.70 (1.10–2.64)	0.017	0.89 (0.42–1.85)	0.750
Bilateral lung transplantation	0.46 (0.14–1.23)	0.142
Operative duration (hour)	1.26 (1.06–1.49)	0.008	1.34 (1.02–1.78)	0.039
Post-transplant bleeding	1.12 (0.64–1.96)	0.678
Postoperative ammonia level	1.02 (1.00–1.03)	0.009	1.02 (1.00–1.04)	0.051
Acute rejection	1.60 (0.59–4.57)	0.359
Primary graft dysfunction, grade 3	1.14 (0.76–1.71)	0.520
Post-transplant AKI	1.08 (0.65–1.80)	0.761
Pre-transplant delirium	3.27 (1.51–7.67)	0.004	2.54 (0.80–8.78)	0.122
BAI, score	1.02 (1.00–1.05)	0.076	1.04 (1.00–1.08)	0.048
BDI, score	1.03 (1.00–1.07)	0.028	1.01 (0.97–1.05)	0.738
Pre-transplant Psychiatrist consult	1.43 (0.92–2.22)	0.109
Pre-transplant Psychiatric medication	1.43 (0.92–2.22)	0.116

OR: odd ratio; aOR: adjusted odd ratio; BMI: body mass index; CCI: Charlson Comorbidity Index; MV: mechanical ventilation; ECMO: extracorporeal membrane oxygenation; AKI: acute kidney injury; BAI: Beck Anxiety Inventory; BDI: Beck Depression Inventory.

Multivariate analysis was adjusted for fixed covariates (age, sex and BMI) and all variables that demonstrated a p value < 0.1 in the univariate analysis.

Impact of postoperative delirium on mortality in LT recipients

The Kaplan–Meier curve showed that patients in the post-transplant delirium group had a lower rate of survival than those without post-transplant delirium (Figure 2). We conducted a Cox regression analysis to assess whether post-transplant delirium was an independent risk factor for mortality. In the multivariable analysis including variables measured before the onset of delirium, increased age (adjusted hazard ratio (aHR), 1.05; 95% CI, 1.03–1.07), pre-transplant MV (aHR; 1.41; 95% CI, 1.05–1.89), postoperative AKI (aHR; 1.77; 95% CI, 1.26–2.48) and postoperative delirium (aHR, 1.37; 95% CI, 1.03–1.84) were each independently associated with higher all-cause mortality (Table 5).

Figure 2.

Kaplan–Meier’s survival curve stratified by post-transplant delirium.

Table 5.

Risk factors for mortality in lung transplant recipients.

Characteristics	Univariate		Multivariate
	HR (95% CI)	p Value	aHR (95% CI)	p Value
Age, years	1.05 (1.04–1.07)	<0.001	1.05 (1.03–1.07)	<0.001
Sex, male	1.08 (0.79–1.46)	0.638	0.75 (0.54–1.04)	0.082
BMI (kg/m2)	1.02 (0.98–1.05)	0.427	0.97 (0.93–1.01)	0.154
CCI, score	1.33 (1.20–1.48)	<0.001	1.13 (0.99–1.30)	0.062
Pre-transplant MV support	1.57 (1.18–2.09)	0.002	1.41 (1.05–1.89)	0.020
Post-transplant AKI	1.90 (1.37–2.65)	<0.001	1.77 (1.26–2.48)	<0.001
Post-transplant delirium	1.56 (1.17–2.08)	0.003	1.37 (1.03–1.84)	0.033

HR: hazard ratio; aHR: adjusted hazard ratio; BMI: body mass index; CCI: Charlson Comorbidity Index; MV: mechanical ventilation; AKI: acute kidney injury.

Multivariate Cox regression analysis was performed by including variables with univariate p value < 0.05 and established clinical risk factors for post-transplant mortality.

Discussion

This study revealed mild anxiety and depression in LT candidates using BAI and BDI assessments. Furthermore, the frequency of psychiatric consultations, medication use and delirium incidence increased significantly after LT. Logistic regression analysis identified higher BMI, prolonged operative duration and increased preoperative BAI scores as significant risk factors for postoperative delirium.

From a perspective of post-LT delirium, key characteristics should be evaluated by thoroughly considering the predisposing patient conditions and post-transplant exacerbating factors. Prolonged waiting times and physical limitations before LT impose significant psychological distress [14]. In this study, 227 (57%) patients required oxygen support therapy before LT, whereas 154 (38.7%) had severe conditions requiring MV. This indicates that a substantial proportion of LT candidates experienced physical limitations.

In our hospital’s LT program, all LT candidates undergo a comprehensive psychiatric evaluation before transplantation, including BAI and BDI assessments and psychiatric consultation. Additionally, to evaluate the adequacy of their support system, we assessed the family relationships and financial status of the candidates. Although no significant differences in marital status or primary caregiver involvement were observed between the groups, this approach facilitates the early identification of high-risk patients who may benefit from timely interventions, such as pharmacological treatment or psychological support.

Additionally, surgical complexity and operative duration, influenced by recipient and donor lung conditions, can contribute to postoperative delirium risk, consistent with previous studies [33].

We selected ammonia levels as a candidate biomarker to identify potential laboratory markers that predict post-LT delirium. Ammonia acts as a neurotoxin [34], potentially contributing to altered consciousness and cognitive dysfunction. Furthermore, ammonia levels may have prognostic value in critically ill patients without hepatic disease [35]. To reduce confounding variables associated with systemic conditions, ammonia levels were specifically analysed on postoperative day 1 to assess their predictive value for delirium. However, our analysis did not show a statistically significant association, aligning with previous findings in liver transplant recipients [36]. The association between ammonia levels and postoperative delirium requires further analysis.

In this study, we focused on postoperative delirium as a primary outcome rather than mortality alone, as it represents a critical intermediate clinical event in the LT recovery process. Delirium is not merely a transient complication, it also demonstrated that patients who developed delirium after LT had a longer postoperative hospital stay and were less likely to be discharged within 60 days [37]. In addition, PFTs performed 1 year after LT showed lower FVC and FEV₁ values in the delirium group compared with those without delirium.

Delirium was significantly associated with increased 2- and 5-year mortality rates and remained an independent risk factor after adjustment for age, sex, BMI, comorbidities, pre-transplant MV and postoperative AKI. Notably, a higher proportion of patients in the delirium group were unable to complete pulmonary function testing owing to poor general condition, indicating delayed recovery and overall physical deterioration. These findings suggest that postoperative delirium reflects a subgroup of patients with slower recovery, impaired functional status and reduced physiological reserve, which may ultimately contribute to their higher long-term mortality.

The notable strengths of this study include its large cohort of approximately 400 LT recipients and the assessment of psychiatric evaluations, delirium occurrence and long-term outcomes. However, there are some limitations. First, as a single-centre study, the generalizability of our findings is limited. In South Korea, the average waiting time from registration to LT is approximately 292 days [38]. The South Korea national lung allocation system is based on medical urgency and classifies candidates into five levels of priority (status 0–4), with status 0 indicating the most critical condition [39]. Patients in this category typically require life-sustaining support, including MV or ECMO. The average waiting time for patients with status 0 is notably shorter (approximately 182 days) [38]. In 2023, 55.4% of LT recipients were listed as status 0 at the time of transplantation [38] – a proportion substantially higher than that reported in Europe or the United States [40,41]. Second, not all patients completed the BAI and BDI assessments owing to this study’s retrospective design. Additionally, post-transplant BAI and BDI scores were unavailable for some patients, preventing direct pre- and post-transplant comparisons. Third, we used the ICDSC score as a dedicated screening tool for delirium; however, for other psychiatric symptoms after LT, detection relied primarily on consultations initiated by patient- or caregiver-reported complaints. Therefore, a selection bias may be present in these cases. Fourth, long-term pulmonary function assessments were not feasible for all patients owing to clinical deterioration, complicating CLAD incidence prediction. Future studies should adopt a longitudinal design to further explore these associations.

In conclusion, this study shows the significant impact of pre-transplant anxiety on post-LT delirium risk. Moreover, postoperative delirium was associated with increased long-term mortality. Therefore, comprehensive psychiatric evaluation and targeted management strategies are necessary to improve post-transplant outcomes. Integrating routine psychological assessments into preoperative evaluations and implementing proactive interventions may help to mitigate the risks associated with psychiatric comorbidities in LT recipients.

Funding Statement

The authors received no financial support for the research, authorship and/or publication of this article.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request