1. Introduction
The pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has pushed worldwide healthcare systems to their limits. Most affected individuals were asymptomatic or suffered from mild flu-like symptoms, while about 15-19% of Swiss patients required intensive care unit (ICU) admission in the first and second wave [
1,
2]. Most ICU patients had underlying comorbidities like hypertension, chronic kidney disease, congestive heart failure, type 2 diabetes mellitus or were immunocompromised [
3,
4].
Reports indicate that critically ill coronavirus disease 2019 (COVID-19) patients who survived the ICU stay frequently reported persistent mental health problems at 1 and 6 months after ICU discharge. Up to one-third of patients experienced moderate symptoms of anxiety and depression, alongside medium to high stress levels.
4 COVID-19 survivors further showed somatic symptoms like loss of appetite, ageusia, anosmia, nausea and diarrhoea, weight- and muscle loss in post-ICU recovery [
5,
6]. Post-acute sequelae of COVID-19 (PASC) encompasses persistent, exacerbated, or newly occurring neuropsychological and physical symptoms following acute COVID-19 illness [
7,
8] These include persistent shortness of breath, reduced mobility, fatigue, and memory impairment [
9] The development of PASC during or after a COVID-19 infection that persists for longer than four weeks and cannot be explained by any alternative diagnosis has been defined as long COVID. At present, the exact definition of long COVID is still evolving [
10,
11]. It poses a substantial challenge to healthcare systems with WHO estimating a prevalence between 10-20% [
12] The elusive diagnosis and lack of treatment options for long COVID often result in referrals to multiple specialists, amplifying healthcare costs [
13].
In this study, we assessed the frequency and severity of long-term complaints in a cohort of COVID-19 patients in need for ICU treatment. Further, we investigated associations between these complaints and clinical risk factors collected during the acute ICU phase. The clinical outcomes focused on psychosomatic aspects alongside respiratory and neurocognitive aspects 12 months after the initial ICU admission. The goal of this study was to identify ICU factors, in addition to pre-existing factors, that may predict 12-month follow-up outcome in severely ill COVID-19 patients.
3. Results
Out of 58 severely ill COVID-19 patients treated in the ICU at the Cantonal Hospital St. Gallen, 22 (~38%) died and 19 (~33%) decided not to participate in this follow-up study. A total of 17 patients (mean age 58.9 ± SD 11.4, range 35–77) were included in the cohort. Death (~38%) and lack of willingness to participate in the follow-up study (~33%) were the main reasons for the small sample size. Missing predictor variables at ICU admission consisted of lung CT data (11.8%) and laboratory data, specifically, lymphocytes (23.5%), interleukin-6 (29.4%), troponin (11.8%), NT-proBNP (17.6%), LDH (5.9%), and D-dimers (29.4%). There were no missing values concerning psychosomatic endpoints. Patients showed 17.6% and 4.8% missing values in the respiratory and neurocognitive endpoints, respectively. In detail, missing data consisted of WatchPAT
TM parameters and items of the MoCA test. Table 1 shows patients’ baseline characteristics symptoms at COVID-19 onset, and the collected data during ICU stay, while
Table S2 shows patients’ nutritional habits at COVID-19 onset.
Table 1.
Baseline and clinical variables during ICU stay.
Table 1.
Baseline and clinical variables during ICU stay.
PATIENT CHARACTERISTICS |
CASES (N = 17) |
Demographics Male sex, n (%) |
13 (76.5) |
Age, years, mean (SD) |
60 (11.4) |
18-30 years, n (%) 31-45 years, n (%) 46-60 years, n (%) 61-75 years, n (%) >75 years, n (%) |
0 (0) 2 (11.8) 7 (41.2) 8 (47) 0 (0) |
Weight, kg, mean (SD) Height, cm, mean (SD) Body mass index (BMI), kg/m2, mean (SD) Years of primary and secondary education, mean (SD) |
90.8 (18) 172.2 (7.3) 30.5 (5.2) 11.4 (3.3) |
Personal medical history, n (%) Any comorbidity Hypertension Cardiovascular disease Chronic lung disease Asthma Dyslipidemia/statin use |
13 (76.5) 9 (52.9) 1 (5.9) 2 (11.8) 2 (11.8) 3 (17.6) |
Symptoms at COVID-19 onset, n (%) Fever Cough Headache Night sweats Chills Shivering Myalgia Joint pain Dyspnea Inspiratory chest pain Retrosternal chest pain Loss of appetite Weight loss |
10 (58.8) 13 (76.5) 11 (64.7) 9 (52.9) 10 (58.8) 10 (58.8) 8 (47.1) 8 (47.1) 9 (52.9) 10 (58.8) 9 (52.9) 10 (58.8) 8 (47.1) |
Findings on lung CT scans at ICU admission, mean (SD) Ground-glass opacity in % of normal lung Crazy-paving in % of normal lung Light consolidation in % of normal lung Heavy consolidation in % of normal lung |
39.0 (4.3) 26.9 (5.8) 8.0 (4.1) 0.4 (0.2) |
Laboratory data at ICU admission, mean (SD) |
|
Hemoglobin in g/l Thrombocytes in G/l1 Troponin in ng/l2 NT-proBNP in ng/l Creatinine in umol/l3 Bilirubin in umol/l CRP in mg/l Leukocytes in G/l Interleukin-6 in pg/ml4 Lymphocytes in G/l D-dimers in ng/ml LDH in IU/l |
128.4 (18.2) 271.1 (117.2) 30.5 (49.7) 758.6 (615.7) 73.2 (24.4) 9.3 (6.1) 208.1 (93.6) 10.2 (3.6) 103.9 (119.3) 0.9 (0.5) 2045 (1384.5) 602.6 (224.8) |
Clinical scores, syndromes and complications during ICU stay |
|
Admission SOFA5 score (SD) Discharge SOFA score (SD) Admission SAPS6 II (SD) Hospital-acquired pneumonia (HAP) more than 48h after hospital admission, n (%) Community-acquired pneumonia (CAP) at hospital admission or within 48h (other than COVID-19), n (%) Acute confusional syndrome, n (%) Acute respiratory distress syndrome (ARDS), n (%) Other complications (acute kidney/hepatic injury, septic shock), n (%) Partial arterial oxygen pressure (PaO2) in mmHg (mean, SD) Fraction of inspired oxygen (FiO2) in % (mean, SD) Highest body temperature in °C (mean, SD) ICU stay duration in days (mean, SD) Hospital stay duration in days (mean, SD) Intubation duration in mechanically ventilated patients in days (mean, SD) |
5.8 (3.4) 2.5 (0.9) 33.6 (12.7)
3 (17.6)
2 (11.8) 5 (29.4) 10 (58.8) 3 (17.6) 59.3 (8.0) 53.1 (18.4) 38.2 (0.8) 13 (9.5) 23 (12.6) 10 (4.1) |
ICU treatment, n (%) Corticosteroid treatment Noradrenalin treatment Prophylactic LMW heparin Low-flow oxygen treatment Non-invasive ventilation (NIV) Mechanical ventilation Extracorporeal membrane oxygenation (ECMO) Intubation Prone position ventilation Tracheostomy Hemofiltration/hemodialysis |
15 (88.2) 5 (29.4) 12 (70.6) 3 (17.6) 5 (29.4) 7 (41.2) 2 (11.8) 9 (52.9) 8 (47.1) 3 (17.6) 0 (0) |
Table S2.
Dietary behavior assessed with the FFQ questionnaire.
Table S2.
Dietary behavior assessed with the FFQ questionnaire.
Nutritional habits at COVID-19 onset Fruit OK (≥2/day) Vegetables OK (≥3/day) Meat OK (≤5/week) Fish OK (≥1/week) Swiss recommendations OK (≥3 of the 4 recommendations above)
|
9 (52.9%) 6 (35.3%) 9 (52.9%) 8 (47.1%) 6 (35.3%)
|
12 (±1) months after ICU discharge, the most frequently reported symptoms were persisting cough (76.5%), headaches (64.7%) as well as anosmia, dysgeusia and loss of appetite in 58.8% of patients. When considering established cut-off points, very few patients showed score values for psychosomatic and neurocognitive diseases at the 12-month follow-up visit.
Figure 1 provides a summary of the descriptive statistical analysis of all endpoints.
Our sample size of 17 patients provided an actual statistical power of 32% based on a post-hoc power analysis with Gpower software for a simple linear regression and an expected medium effect size (Cohen’s F2) of 0.15 [
28]. Based on univariate linear, logistic, and ordinal regression analyses, we identified several variables associated with long-term outcomes. However, these findings did not remain statistically significant after Bonferroni adjustment for multiple testing.
Figure 2 and
Figure 3 show two heatmaps representing p-values and effect sizes in order to illustrate health clusters between predictors and associated endpoints. The following two examples illustrate how to read the figures: A high CRP was positively correlated with a higher score in the FSS questionnaire indicating worse fatigue in a statistically relevant way with a medium effect size (adjusted R2). Extracorporeal membrane oxygenation (ECMO) was negatively associated with total lung capacity (TLC) in a statistically relevant way and was therefore associated with a smaller lung capacity with a medium effect size (adjusted R2).
Inflammatory or infectious (CRP, lymphocytes), cardiac (troponin, NT-proBNP), renal (creatinine), and hematologic (hemoglobin) markers were among the most promising predictors. Other relevant predictors consisted of ICU clinical severity (SOFA, SAPS II, need for mechanical ventilation), complications (ARDS), and lung CT data (ground-glass opacity). The main endpoints associated with these predictors were psychosomatic outcome measures (fatigue, depressive, and anxiety symptoms) and sleep problems (sleep apnea, insomnia). In particular, higher levels of inflammation (CRP, lymphocytes) predicted worse outcome of fatigue, depression, and anxiety. The presence of ARDS and worse ICU severity scores (SOFA, SAPS II) were further predictors for worse depression and anxiety symptoms. The need for mechanical ventilation was significantly associated with higher depression scores. Concerning these affective symptoms, high hemoglobin and creatinine levels were associated with a better outcome. Cardiac makers (troponin, NT-proBNP) were further positively associated with sleep apnea. Ground-glass opacity in the lung CT scans was positively associated with depression, anxiety, fatigue, and insomnia levels and an overall impairment of quality of life.
4. Discussion
Our study provides several main results. The higher the disease severity in the acute phase of COVID-19, the more likely patients in need for ICU treatment will suffer from long-term sequelae. Higher levels of inflammatory markers, higher ICU severity scores and markers of organ dysfunction – e.g., the need for mechanical ventilation, more ground-glass opacities in the lung CT scan, presence of ARDS and elevated cardiac biomarkers – were associated with worse outcome of fatigue and affective symptoms such as depression and anxiety. While higher hemoglobin and creatinine levels seemed to be protective factors for those.
Multiple neurological, cardiopulmonary, gastrointestinal, and dermatological symptoms, described as the multiorgan phenotype (MOP) of acute COVID-19, were linked to an elevated risk of protracted recovery.
9 When hospitalization was required, Evans and colleagues
7 identified female sex, obesity, and invasive mechanical ventilation in COVID-19 patients as associated with lower likelihood to recover full quality of life with a substantial deficit in median EQ-5D-5L index score at one year after discharge. They further found a correlation between increased inflammatory mediators (including interleukin-6) and cognitive impairment at 5 months, emphasizing the idea of persistent systemic inflammation and its consequences on cognitive performance.
7 In our study, we confirmed the association of inflammatory markers (CRP, lymphocytes) with fatigue and affective symptoms. Irwin, Olmstead and Carroll [
35] concluded that there is a growing body of evidence linking sleep disturbances to the risk of inflammatory diseases and all-cause mortality, possibly through effects of sleep disturbances on two systemic inflammatory markers (CRP, interleukin-6). Our results showed the same relation as CRP (but not interleukin-6) positively predicted fatigue, however with a small effect size. Recently a correlation was shown between higher CRP in the general population and reduced sleep quality and increased fatigue, corroborating our findings. [
36,
37,
38,
39,
40] Al-Hakeim et al. [
41] mentioned the significant role of activated immune-inflammatory and oxidative and nitrosative stress (IO&NS) pathways in determining the long-term outcome of a COVID-19 infection. Chronic fatigue syndrome (CFS), major depression (MD), and generalized anxiety disorder (GAD) are all characterized by activated IO&NS pathways and increased levels of inflammatory mediators, including CRP [
37]. Six months or more after SARS-CoV-2 infection, elevated CRP levels are significantly associated with concomitant fatigue severity [
42]. In contrast to the positive correlation observed between elevated lymphocyte levels and fatigue in our study, Swanink et al. [
43] did not find any significant changes in absolute lymphocyte counts among patients with chronic fatigue syndrome (CFS) and the control group. However, aligning with our findings, Zheng et al. [
44] described low levels of lymphocytes in acutely infected COVID-19 patients.
Similar to our study, Naudé et al. [
45]. described a correlation between elevated CRP levels and depression as well as generalized anxiety disorder. Furthermore, Azevedo et al. [
46] demonstrated that patients who suffered from both SARS-CoV-2 infection and major depression showed notably higher CRP levels compared to COVID-19 patients without concurrent depression. It is plausible that inflammatory markers may help predicting the long-term mental health outcome of COVID-19 and identify patients with fatigue and affective disorders.
One severe complication of the SARS-CoV-2 virus is acute respiratory distress syndrome (ARDS), which affected more than half of our patients. In our analysis, presence of ARDS predicted 12-month anxiety. A multi-site, longitudinal cohort study found that ARDS survivors experienced persistent psychiatric issues, anxiety, depression, and posttraumatic stress disorder [
47]. Palakshappa et al. [
48] reported similar outcomes involving 629 patients from three different trials with a significant proportion of ARDS survivors having substantial mental health symptoms. The prevalence of substantial symptoms of depression, anxiety, and PTSD at 6 months reached 36%, 42%, and 24%, respectively. Our study revealed a significant association between mechanical ventilation, the presence of ARDS, and depressive symptoms. Pre-pandemically, depressive symptoms one year after discharge had been reported in ICU survivors of mechanical ventilation, but to our knowledge not previously described in COVID-19 [
49].
It is widely recognized that anemia can lead to symptoms such as fatigue, irritability, and concentration problems, which are often associated with depression components. However, findings from a large cohort study conducted by Lever van Milligen et al. [
50] and another study by Chen et al. [
51] failed to provide significant evidence of a direct connection between depression, anxiety, and hemoglobin levels. In a study by Jackowsa et al. [
52] a positive relationship between hemoglobin levels and sleep duration was observed. Our data showed that higher hemoglobin levels were associated with lower scores in depression and anxiety questionnaires. Concerning protective factors against depression and anxiety, our data further identified higher levels of creatinine being associated with lower depression scores. The scientific evidence on the correlation between creatinine and affective symptoms such as depression or anxiety is sparse and incongruent. One study by Ibrahim et al. [
53] reported no association between creatinine and depression, while a study by Ogrizovic et al. [
54] found a positive correlation between creatinine and depression. The findings of Bossola et al. [
55] showed that patients with lower creatinine were more depressed.
Concerning the Sepsis-Related Organ Failure Assessment (SOFA) score at ICU admission, we observed elevated scores for both HADS scores, assessing anxiety and depression, along with a low self-assessment of current health in our patients. This correlation is plausible, as the prolonged ICU stay, poor and critical condition as well as the uncertainty and anxiety experienced by the patients directly impact mental health. [
56] Similar findings emerged in evaluating the Simplified Acute Physiology Score (SAPS) II even outside of COVID-19. [
57] The lung diffusion capacity 12-months after ICU stay was reduced in patients with an elevated SOFA score at ICU discharge. This is likely multifactorial including pulmonary edema, which decreases the gas exchange surface area and consequently lowers DLCO, inflammation and subsequent fibrosis. [
57]
In our study, both heart failure markers troponin and NT-proBNP positively predicted higher Apnoea-Hypopnoea Index (pAHI) scores with large effect sizes. Sasaki et al. [
58] demonstrated a correlation between elevated NT-proBNP levels and sleep difficulties, as well as short sleep duration, which aligns with our findings. Several studies have reported that poor sleep is a risk factor for coronary heart disease and stroke. [
59,
60,
61] However, there are limited data regarding the association between poor sleep and heart failure. Laugsand et al. [
62] stated a positive relationship between the number of insomnia symptoms, namely the difficulty initiating or maintaining sleep and having nonrestorative sleep, and heart failure. Concerning sleep apnea, Hübner et al. [
63] and Tasci et al. [
64] found no correlation between changes in NT-proBNP and the pAHI as measured by the WatchPAT
TM which contrasts with our findings of a positive prediction. In contrast, Vartany et al. [
65] found no correlations between the evening baseline or post-sleep NT-proBNP levels and obstructive sleep apnea syndrome (OSAS). Lazzarino et al. [
66] reported that certain individuals, when exposed to intense stress or exhibiting exaggerated stress responses, release both inflammatory factors and cardiac troponin in response. This observation mirrors the elevated troponin levels in stress-induced Takotsubo cardiomyopathy [
67,
68]. Several studies have further demonstrated an association between sleep apnea and increased troponin levels. However, this association lost statistical significance after adjusting for cardiovascular risk factors [
69,
70].
In analyzing our lung CT data, ground-glass opacity showed notable associations with some endpoints. Patients with pulmonary ground-glass opacity scored worse in depression, anxiety, fatigue, and insomnia questionnaires. In addition, these patients experienced an overall lower quality of life. Compared with initial lung CT scans, 78% of the COVID-19 hospital survivors still had some pulmonary ground-glass opacity showing up on lung scans at a one-year follow-up [
71]. These residual lesions are further associated with lower peripheral oxygen saturation as it was the case in our patients [
72]. To our knowledge our study is the first to describe pulmonary ground-glass opacity as predictor of depression, anxiety, fatigue, and insomnia scores.
This study has several limitations. Most importantly, the small sample size of 17 patients resulted in a low statistical power. Therefore, the results have to be interpreted cautiously. Secondly, despite having pre-post COVID-19 difference scores for several neurocognitive endpoints (e.g., B-ADL, external cognitive assessment), other endpoints lacked a pre-COVID-19 reference value. For instance, we had no data on the psychosomatic or respiratory health prior to the COVID-19 and ICU stay, e.g., depressive symptoms or 6-minute walk test performance. Conversely, the strengths of our study consisted of a broad range of interdisciplinary predictors and endpoints using detailed validated questionnaires as well as the identification of novel associations between ICU factors and relevant long-term health outcomes in COVID-19.
Author Contributions
Conceptualization, W.C.A., D.A.S., and C.R.K.; Methodology, W.C.A., N.G., K.G.F., T.Fi., G.R.K, M.Fr., M.H.B., and D.A.S.; Software, N.G.; Validation, G.R.K, U.P., M.Fr., M.H.B., D.A.S., and W.C.A.; Formal Analysis, N.G. and D.A.; Investigation, D.A., K.G.F., T.Fi., and T.Fr.; Resources, W.C.A., G.R.K, U.P., M.Fi., M.H.B., T.Fr., M.B., and D.A.S.; Data Curation, N.G. and D.A.; Writing – Original Draft Preparation, N.G., D.A., and W.C.A.; Writing – Review & Editing, W.C.A., D.A.S., M.Fr., M.B., and T.Fi.; Visualization, N.G.; Supervision, W.C.A. and D.A.S.; Project Administration, W.C.A. and D.A.S.; Funding Acquisition, W.C.A., G.R.K., U.P., M.H.B., and D.A.S. Reading and approval of final manuscript: All authors.