
==== Front
Eur J Phys Rehabil Med
Eur J Phys Rehabil Med
EJPRM
European Journal of Physical and Rehabilitation Medicine
1973-9087
1973-9095
Edizioni Minerva Medica

38903009
8207
10.23736/S1973-9087.24.08207-8
Article
Pulmonary rehabilitation in follow-up and inpatient rehabilitation for Long COVID: twelve months of follow-up
RUTSCH Mercedes 1 *
BUHR-SCHINNER Heike 2
GROSS Thomas 3
SCHÜLLER Per O. 4
DECK Ruth 1
1Department of Rehabilitation Sciences, Institute for Social Medicine and Epidemiology, University of Lübeck, Lübeck, Germany; 2Ostseeklinik Schönberg-Holm, Schönberg-Holm, Germany; 3Reha-Zentrum Schömberg, Schömberg, Germany; 4MEDIAN Klinik Flechtingen, Flechtingen, Germany
* Corresponding author: Mercedes Rutsch, Department of Rehabilitation Sciences, Institute for Social Medicine and Epidemiology, University of Lübeck, Ratzeburger Allee 160, 23562 Lübeck, Germany. E-mail: mercedes.rutsch@uksh.de
Authors’ contributions: Mercedes Rutsch and Ruth Deck contributed substantially to the conception and design of the study; Heike Buhr-Schinner, Per O. Schüller and Thomas Gross provided support in data interpretation and provided the necessary clinical input. All authors read and approved the final version of the manuscript.

20 6 2024
8 2024
60 4 716728
21 5 2024
11 4 2024
29 8 2023
2024 THE AUTHORS
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives (CC BY-NC-ND) 4.0 License.
BACKGROUND

Individuals with persistent impairments due to Coronavirus disease 2019 (COVID-19) can receive pulmonary rehabilitation in Germany. To date, there is no evidence of the medium- or long-term effects of pulmonary rehabilitation on Long COVID.

AIM

This study examined changes in health and occupational outcomes over time and described the therapeutic content of pulmonary rehabilitation and aftercare. This analysis also compared two rehabilitation groups after COVID-19 who had different levels of access to rehabilitation.

DESIGN

Longitudinal observational study with multicenter and prospective data collection.

SETTING

Pulmonary rehabilitation in four different rehabilitation facilities in Germany.

POPULATION

Individuals with a mild course of disease and long-lasting impairments (inpatient rehabilitation, IR) and patients with a severe course after hospitalization (follow-up rehabilitation, FuR). Participants had to be between 18 and 65 years of age.

METHODS

Written questionnaires were administered at the beginning and end of rehabilitation, as well as six and twelve months after rehabilitation. Health-related quality of life (HrQoL), fatigue, participation restrictions, COVID-19 symptoms, mental and physical health were assessed, as well as occupational outcomes and questions about rehabilitation and aftercare.

RESULTS

IR patients were predominantly female (68.0%) and 52 years of age on average, while 66.1% of Long COVID rehabilitees in FuR were male and three years older. Over the course of rehabilitation, most COVID-19 symptoms decreased with statistical significance. The subjective health scales showed improvements with medium to large effect sizes (ES) over time in IR (P<0.01; ES between 0.55 (cognitive fatigue) and 1.40 (physical fatigue)) and small to large effects in FuR (P<0.01; ES between 0.45 (anxiety) and 1.32 (physical fatigue)). One year after rehabilitation, most effects remained at a moderate level. After twelve months, an increase in neurocognitive symptoms was observed in FuR patients. More than 80% of employed people returned to work one year after rehabilitation, although FuR patients returned to work a median of four weeks later (P<0.01).

CONCLUSIONS

The comparative analysis showed that rehabilitees in different forms of rehabilitation attended rehabilitation with different impairments and rehabilitation goals, which are partly considered in treatment and aftercare.

CLINICAL REHABILITATION IMPACT

To provide needs-based rehabilitation to different rehabilitation groups with Long COVID, knowledge of their health histories and preferences is necessary.

Key words:

Rehabilitation
Post-acute COVID-19 syndrome
Health status
==== Body
pmcInfection with SARS-CoV-2 can vary in severity and acute treatment but also in the length of persistent symptoms. Finally, a certain proportion of infected people do not recover from COVID-19 and report persistent symptoms lasting from four to twelve weeks (ongoing symptomatic COVID-19) or more than twelve weeks (post-COVID-19 syndrome).1 In line with the NICE guidelines, the following manuscript uses the term Long COVID, as this covers both ongoing symptomatic COVID-19 and post-COVID-19 syndrome.1 Currently, there is no reliable estimate of the prevalence of Long COVID, but studies have identified various risk factors associated with Long COVID, such as older age, hospitalization, smoking, overweight, poor general or mental health, female sex and asthma.2, 3 The most common symptoms of Long COVID are fatigue, dyspnea, headache and attention disorder, but a meta-analysis identified over 50 more symptoms.4 As a result of long-lasting symptoms, the physical, mental and cognitive impairments caused by SARS-CoV-2 infection can limit participation in daily life, health related quality of life (HrQoL) and the ability to work.5

There is currently no causal or pharmacological therapy for the treatment of Long COVID, as the pathology is not yet fully understood. According to a systematic review, 44% of the 388 studies analyzed reported rehabilitation as the most common intervention in Long COVID.6 However, there is no uniform or evaluated concept for the rehabilitation of people with Long COVID. Currently, guidelines recommend rehabilitation that targets the symptoms in a specialist department (e.g., pulmonology, neurology, psychosomatics) according to the primary limitations.7 The same symptom-based therapy applies to rehabilitation aftercare to treat impairments that persist beyond the three-week rehabilitation period.7 In addition to further treatment of existing impairments, the rehabilitee needs support in transferring rehabilitation skills to everyday life, which is difficult for many rehabilitation patients.8

Changes in the health status of Long COVID patients during rehabilitation has been demonstrated in several reviews and observational studies. According to the publications, rehabilitation for Long COVID takes place most often in pulmonary departments. Bailly et al. reviewed 35 studies and concluded that rehabilitation, including physical activity, has a health benefit for patients after COVID-19.9 In addition to functional capacity, HrQoL, dyspnea, mental health and general health improve during rehabilitation.9-14 In a comparative analysis among people with mild versus severe COVID-19, pulmonary rehabilitation also showed improvements at the time of discharge for both groups.15 People with a severe course improved more in terms of outcomes, but they also started rehabilitation with greater impairment. In addition to improving health, medical rehabilitation aims to restore the rehabilitee’s ability to work, which may be limited by existing physical and psychological impairments. People with Long COVID take an increased number of sick days16 and report a reduced subjective ability to work.17, 18 Accordingly, at the start of rehabilitation, Long COVID rehabilitees estimate their ability to work and their performance to be reduced by half.13 At the end of rehabilitation, almost one in two patients is discharged fit for work, which is considerably higher than in the psychosomatic and psychocardiology comparison groups of a trial.11 However, previous studies focusing on health status and occupational development are limited due to their measurement only at the beginning and end of rehabilitation.14, 15 But it is particularly important to know whether rehabilitation success and participation in everyday life can be maintained in the long term, or whether the intervention has only a short-term effect. In addition, a stable return to work cannot be measured at the end of rehabilitation, but only with some follow-up.

Overall, there are already basic data on rehabilitation for people with Long COVID, but the evidence on this topic is still insufficient, and several reviews mention the poor quality of previous studies (retrospective, small number of cases, lack of comparison group, no consistent survey instruments, poor description of the intervention).10, 19, 20 In addition, there has been only one study with follow-up but no comparison between two rehabilitation groups.13 Most studies to date have not provided evidence on the medium- or long-term success of rehabilitation.11, 14, 15

Due to the lack of longitudinal data on Long COVID rehabilitants,14, 15 the missing evident rehabilitation and aftercare program for Long COVID,21 and the overarching goal of rehabilitation to restore employment,21 the objectives of this study are as follows: This investigation analyses on how the health of different groups of Long COVID rehabilitees changes during rehabilitation and in the time afterwards. The collected data will provide information on whether rehabilitees return to work and how work-related parameters develop in the year following rehabilitation. In addition, this study is intended to describe the content of the therapy and patient satisfaction. Since rehabilitation clinics attend to two different groups of Long COVID patients, those who come directly after an inpatient hospital stay and those who come months after a mostly mild infection, in this study, these two groups were differentiated and compared with each other.

Materials and methods

Study design and participation

This was a longitudinal, prospective observational study with a mixed-methods design conducted from 11/2020-11/2023. Quantitative data collection included questionnaire surveys at four measurement points (start of rehabilitation, end of rehabilitation, six and twelve months after rehabilitation). Recruitment took place between February 2021 and February 2022. We invited employable Long COVID patients in inpatient rehabilitation (IR) and follow-up rehabilitation (FuR) to participate in the study. We also recruited a comparison group for the overall study, consisting of asthma and COPD patients. Participants had to be between 18 and 65 years of age and undergo rehabilitation for either COVID-19 or the comparison group indication. Furthermore, German language skills had to be sufficient to be able to answer the questionnaires. Individuals whose rehabilitation was funded by the German Statutory Accident Insurance were not included in this study. Patients gave written informed consent for study participation. Further details on this study can be found in the study protocol.22 Due to the relevance of the research subject, two interim evaluations of this study have been published, but the papers differ in terms of the research question and do not include any comparison. This paper focuses on quantitative data from Long COVID rehabilitation patients.

Ethics

The Ethics Committee of the Medical Faculty of the University of Lübeck raised no ethical, medical or legal objections to the study and approved the study (AZ 20-391). The trial has been registered with the German Clinical Trials Register under the code DRKS00023642.

Setting

Medical rehabilitation in Germany is characterized as a multidisciplinary and interprofessional intervention that is under medical supervision. Employed individuals with a chronic illness whose ability to work is limited or at risk can apply for IR through German Pension Insurance (Deutsche Rentenversicherung, DRV). Individuals with poor health who have been treated in the hospital can apply for FuR after their hospital stay. For both forms of rehabilitation, the statutory insurance requirements have to be fulfilled, and the need for rehabilitation, the ability to rehabilitate and the prognosis for rehabilitation have to be examined.

Rehabilitation in Germany can be either outpatient or IR and lasts 21 days, which can be extended if necessary. In our study, rehabilitation took place exclusively as inpatient treatment, so the patients stayed at the rehabilitation clinic for 21 days. Patients attended an average of 4 (2 to 6) therapy sessions five days a week, and the average number of therapy hours per day was approximately 4.5 hours (2.5-6.5 hours).

Participants for this study were recruited from four German rehabilitation facilities. The therapy concept in medical rehabilitation is based on the biopsychosocial model. The rehabilitees did not receive an intervention in the strict sense but rather a multidisciplinary pulmonary rehabilitation adapted by the clinics for Long COVID. Therapy for Long COVID is primarily based on the main symptoms and individual rehabilitation goals. Eligible rehabilitees were approached and informed about study participation at the beginning of their rehabilitation by a staff member from the local clinic. The clinics assigned each participant an identification number (ID), which provided a link to the questionnaire data across all measurement points. The clinic employees kept a file in which the name and ID were linked, without linkage to the questionnaire data. At the university institute, the documentation and merging of data took place anonymously via the IDs.

Survey instruments

The rehabilitation patients completed a questionnaire in the rehabilitation clinic at the beginning (t0) and at the end (t1) of their rehabilitation. The follow-up questionnaires were sent by mail to the patients six (t2) and twelve (t3) months after rehabilitation by a mandated employee in the clinic. The questionnaire consisted of 10 to 16 pages and included standardized survey instruments and individual items.

Impairment of social and occupational participation was measured by the IMET.23 This questionnaire is based on the limitations of participation mentioned in the International Classification of Functioning, Disability and Health. The instrument assesses participation restrictions in nine areas relevant to everyday life on a scale from zero to ten. The sum score ranges from zero to ninety points, with high values indicating high participation limitations.

HRQoL was assessed with the Veterans RAND 12-Item Health Survey (VR-12). The VR-12 includes twelve items that represent a physical and mental sum scale.24 On the VR-12 summation scale, high scores indicate high mental or physical quality of life.

The Depression Anxiety Stress Scales capture the core symptoms of depression, anxiety and stress. In this survey, the German-language short version with a total of 21 items was used.25 Each of the three subscales (depression, stress, anxiety) consists of seven items.25 High scores indicate high levels of impairment. The cut-off values for the depression and stress scales are ten, and the anxiety scale has a cut-off of six points.

The Patient Health Questionnaire (GAD-7)26 and the Patient Questionnaire PHQ-927 assess generalized anxiety disorder and depressiveness. Again, high scores represent high levels of impairment. The cut-off values are 5, 10 and 15 and indicate mild, moderate or severe depression or anxiety disorder.

The EORTC-FA12 measures physical, emotional and cognitive impairment due to fatigue.28 The survey instrument consists of twelve questions and results in three scales, which indicate high levels of fatigue-related impairment.

The COPD Assessment Test (CAT)29 assesses pulmonary impairment. A high score indicates high impairment. In addition, shortness of breath was recorded with five dichotomous items.

These parameters represent the spectrum of subjective health of the rehabilitation patients at the different measurement points. In addition, participants were asked about twenty COVID-19 symptoms.

Subjective work ability was measured with the Work Ability Score of the Work Ability Index.30 The scale ranges from zero to ten, and a higher score indicates higher work ability.31 Subjective employment prognosis was measured by the SPE scale. The question tool consists of three items that can be aggregated to a risk score.32

In addition, performance in the areas of work, everyday life and leisure was measured with three scales from zero to ten. A high value indicates high performance in the respective area.33 Periods of incapacity to work, occupational stress and changes were reported by the participants themselves.

Finally, at the end of rehabilitation, the therapies used were recorded with individual items, and participants were asked about their satisfaction with rehabilitation and rehabilitation success. Questions about rehabilitation aftercare were also asked during follow-up.

The severity of COVID-19 was documented on site by the clinic staff in accordance with the Robert Koch Institute recommendation.34

Statistical analysis

Descriptive analysis for nominal and ordinal scaled variables included contingency tables using χ2 and McNemar tests. Descriptions of health and occupational courses are presented for interval-scaled outcomes using paired-sample t-tests. Analysis of time courses for non-normally distributed metric variables and two independent samples comparisons for ordinal scaled variables were performed with the Mann-Whitney U test. To determine within-group effect sizes (ES), Cohen’s d was calculated by standardizing mean differences at the standard deviation of prevalence values.35 The interpretation of ES followed Cohen (d≥0.2, small effect, d≥0.5, medium effect, d≥0.8, large effect).36 Comparisons between the two groups of patients were made using mixed model ANOVA. Missing values were excluded from analyses, and missing values for the different scales were handled according to the instructions of the test authors. In principle, a complete case analysis was carried out. Analyses of occupational parameters included only those individuals who reported being employed full-time or part-time at baseline. The statistic software IBM SPSS Statistics Version 22 was used for statistical analysis. Significance was defined as α<0.05.

Results

Participants and dropout

The study sample consisted of 344 participants. The sample was composed of 253 IR patients and 91 FuR patients. One person abandoned rehabilitation treatment, and two individuals were transferred back to the hospital. Eleven participants did not complete the questionnaire at the end of rehabilitation. Thus, at the end of rehabilitation, data on the first two measurement points were available from 241 people in the IR group and 89 people in the FuR group. In the follow-up survey six and twelve months after rehabilitation, 221 and 172 individuals in IR, respectively, answered the questionnaire. In the FuR group, 74 participants answered after six months and 63 after twelve months. We had no information about the reasons for the dropouts during follow-up. Figure 1 shows the flow chart of the study participant selection process.

Figure 1 —Flow chart of the study participant selection process.

Dropout analysis was performed separately for both groups (IR and FuR). The analysis included sociodemographic data and subjective health status at admission. Dropouts from FuR had a less severe course of initial COVID-19 disease (P=0.027). Otherwise, there were no statistically significant differences between participants and dropouts with regard to sociodemographic or health status. The results of the dropout analysis are attached in the Supplementary Digital Material 1, Supplementary Table I.

Sample description

The IR group was predominantly composed of women (68%), while the participants in the FuR group were predominantly male (66.1%). On average, the participants in IR were significantly younger than patients in FuR. Most of the study participants had a vocational qualification and had a high school or college education. In addition to Long COVID, rehabilitees often had two other diseases. There was a statistically significant difference between the two groups in terms of hospitalization, ICU admission, and ventilation. The small number of cases with treatment information was due to a skipped instruction in the questionnaire. In the IR group, COVID-19 was initially mainly mild or moderate (83.1%), and FuR patients primarily had a severe or critical (77.8%) course. Table I summarizes the sample.a

Table I —Description of the sample.

	N.	IR	N.	FuR	P value groups	
Gender, N. (%)		
Female
Male
Other	169	115 (68.0)
53 (31.4)
1 (0.6)	62	21 (33.9)
41 (66.1)	<0.01*	
Age [years], M (SD; R)	172	52.3 (8.7; 25-65)	63	55.6 (7.1; 33-65)	<0.01*	
Education level, N. (%)						
Max. lower education
Secondary school
Higher education	169	20 (11.8)
82 (48.5)
67 (39.6)	62	8 (12.9)
29 (46.8)
25 (40.3)	0.962	
Vocational education, N. (%)	
None
Vocational school
University	169	4 (2.4)
131 (77.5)
34 (20.1)	62	3 (4.8)
45 (72.6)
14 (22.6)	0.551	
Comorbidities, score, M (SD; R)	172	2.5 (1.9; 0-9)	63	2.2 (1.9; 0-8)	0.313	
Treatment, N. (%)	
Hospitalization	164	60 (36.6)	60	56 (93.3)	<0.01*	
Intensive care treatment	83	15 (18.1)	54	34 (63.0)	<0.01*	
Ventilation	56	7 (12.5)	52	16 (30.8)	0.02*	
Oxygen at start of rehabilitation	163	9 (5.5)	63	18 (28.6)	<0.01*	
Severity of COVID-19, N. (%)	
Mild
Moderate
Severe
Critical	172	81 (47.1)
62 (36.0)
26 (15.1)
3 (1.7)	63	2 (3.2)
12 (19.0)
25 (39.7)
24 (38.1)	<0.01*	
IR: inpatient rehabilitation; FuR: follow-up rehabilitation; SD: standard deviation; M: mean; N: total number; R: range. *Statistically significant differences between the two groups.

Health status over time

The rehabilitees showed great physical and mental limitations at the time of admission to the rehabilitation clinic. During rehabilitation, the study participants improved their health status mostly with medium to large effects (P<0.01). At follow-up, the outcomes showed different developments: while participation restrictions and impairments in physical quality of life continued to be reduced after rehabilitation, restrictions in fatigue and mental health outcomes increased. However, the baseline level of restriction was solely assumed in the mental dimension of HrQoL. The individual measurement points, the corresponding ES and the results of the mixed ANOVA are reported in Supplementary Digital Material 2, Supplementary Table II.

Symptoms

The most common symptoms reported by Long COVID rehabilitees at admission were dyspnoea, tiredness, lack of strength and exhaustion. During rehabilitation, most of the symptoms decreased significantly, especially the symptoms that affected performance. During follow-up, symptom burdens took different courses: some symptoms continued to decrease, and others were more present. On average, the IR patients reported 16 symptoms at the start of rehabilitation and 15 symptoms twelve months after rehabilitation. The FuR patients were affected by 14 symptoms at the start of rehabilitation and twelve months after rehabilitation. The IR patients showed significantly more symptoms at the start of rehabilitation than FuR patients (P=0.028). The prevalence and detailed course of COVID-19 symptoms, as well as a group comparison, are provided in Supplementary Digital Material 3, Supplementary Table III.

Occupational outcomes

Employment and ability to work

At the start of rehabilitation, most of the rehabilitees were employed. At the last measurement point, three of the IR patients reported that they were no longer working. The days of incapacity to work, always within the last six months, decreased significantly between baseline and the twelve-month follow-up (P<0.01). Occupational performance and the subjectively perceived ability to work improved significantly over time (P<0.01). Evaluations of employment were performed only for individuals employed at baseline and are presented in Table II.

Table II —Employment and ability to work.

	N.	IR	N.	FuR	P value groups	
Employed at baseline, N. (%)	170	138 (81.2)	60	45 (75.0)	0.15	
Return to work, N. (%)	
6 months after rehabilitation
12 months after rehabilitation	138
137	117 (84.8)
119 (86.9)	44
44	36 (81.8)
39 (88.6)	0.668
0.535	
Time between rehabilitation and RTW [week], median (Q1-Q3)	112	1 (0-3.0)	36	5.5 (1.25-13.75)	<0.01*	
Incapacity to work [week], M (SD)	
Baseline
6 months after rehabilitation
12 months after rehabilitation	119	11.5 (8.7)
5.3 (8.8)
3.9 (7.8)	34	8.5 (5.5)
9.7 (10.6)
2.6 (7.4)	<0.01*
<0.01*
0.399	
Occupational performance, M (SD)	
Baseline
6 months after rehabilitation
12 months after rehabilitation	109	3.9 (3.1)
5.7 (2.7)
5.7 (2.6)	35	2.9 (3.5)
6.3 (2.5)
6.7 (2.6)	0.062
0.060
0.174	
Subjectively perceived ability to work, M (SD)	
Baseline
6 months after rehabilitation
12 months after rehabilitation	136	4.1 (2.9)
5.6 (2.8)
5.9 (2.6)	42	3.4 (2.9)
6.6 (2.6)
6.4 (2.8)	0.099
0.044*
0.237	
IR: inpatient rehabilitation; FuR: follow-up rehabilitation; SD: standard deviation; M: mean; N: number; RTW: return to work; Q1-Q3: interquartile range. *Statistically significant differences between the two groups.

Subjective prognosis of employment

The risk of discontinuing employment because of health conditions decreased over time in both groups. Twelve months after rehabilitation, 26.2% (FuR) and 33.1% (IR) of respondents still had an increased risk of leaving the labor market prematurely. Among IR patients, there was a significant increase to 20.6% of those who were thinking about applying for a pension (P=0.045). In addition, there were no statistically significant differences in the SPE scale between the groups or over time. Table III shows the items of the SPE scale and the risk score over time.

Table III —SPE Scale.

		% yes1	P value2 time	
	Group	t0	t2	t3	t0-t2	t0-t3	
Do you believe that you will be able to work until you reach retirement age?	IR	43.5	43.7	51.9	1.0	0.188	
FuR	48.9	57.1	58.1	0.508	0.388	
Is your ability to work permanently threatened by your current health state?	IR	40.6	37.3	35.7	0.728	0.710	
FuR	40.0	31.0	28.6	0.424	0.210	
Are you currently thinking about applying for a pension?	IR	12.4	20.0	20.6	0.089	0.045*	
FuR	17.8	16.7	27.9	1.0	0.344	
high risk score	IR	39.4	38.8	33.1	1.0	0.472	
FuR	37.8	28.6	26.2	0.424	0.180	
IR: inpatient rehabilitation; FuR: follow-up rehabilitation; t0: start of rehabilitation; t1: end of rehabilitation; t2: six months after rehabilitation; t3: twelve months after rehabilitation;1for employed individuals at baseline: FuR N= 45 and IR N=138; 2McNemar. *Statistically significant differences over time.

Occupational changes

Twelve months after pulmonary rehabilitation, one-third of the study participants had experienced occupational changes. The most common changes were a reduction in weekly working hours or a change of employer. There were no significant differences between the groups. Figure 2 shows how many people experienced one or more of the listed occupational changes in the twelve months after rehabilitation.

Figure 2 —Occupational changes.

Pulmonary rehabilitation

Therapies during rehabilitation

Pulmonary rehabilitation lasted 27 days. The median time between infection and IR was five months (Q1-Q3: 4.0-9.5). For FuR patients, the median time between infection and the start of rehabilitation was one month (Q1-Q3: 1.0-2.0). The Long COVID rehabilitees underwent multidisciplinary pulmonary rehabilitation. Almost all rehabilitation patients participated in endurance exercise, respiratory physiotherapy and information sessions. FuR patients were significantly more likely to participate in respiratory muscle training. In contrast, people in IR participated more often in relaxation exercises, physiotherapeutic treatments, psychological counselling, gymnastics, vocational integration support and creative therapy. The treatments received by the groups are shown in Table IV.

Table IV —Treatments received during pulmonary rehabilitation.

	IR, N. (%)	FuR, N. (%)	P value1 groups	
Endurance exercises	166 (96.5)	57 (91.9)	0.144	
Respiratory physiotherapy	162 (94.2)	58 (93.5)	0.856	
Information sessions	161 (93.6)	56 (90.3)	0.393	
Relaxation exercises	128 (74.4)	37 (59.7)	0.029*	
Inhalation exercises	127 (73.8)	46 (74.2)	0.956	
Strength endurance training	123 (71.5)	46 (74.2)	0.686	
Physiotherapeutic treatments	118 (68.6)	28 (45.2)	<0.01*	
Psychological counselling	111 (64.5)	31 (50.0)	0.045*	
COVID-19 conversation group	105 (61.0)	37 (59.7)	0.850	
Social counselling	101 (58.7)	30 (48.4)	0.160	
Nutrition course	96 (55.8)	39 (62.9)	0.333	
Respiratory muscle training	94 (54.7)	50 (80.6)	<0.01*	
Occupational therapy	90 (52.3)	31 (50.0)	0.753	
Gymnastics	90 (52.3)	23 (37.1)	0.040*	
Play-based exercises	62 (36.0)	30 (48.4)	0.088	
Vocational integration support2	41 (29.7)	6 (13.3)	0.029*	
Smoking cessation course3	2 (28.6)	N/A	N/A	
Stress management course	44 (25.6)	9 (14.5)	0.074	
Internet-based aftercare	25 (14.5)	9 (14.5)	0.997	
Creative therapy	11 (6.4)	0	0.041*	
Group talk aftercare	8 (4.7)	5 (8.1)	0.314	
Work-related therapy2	5 (3.6)	3 (6.7)	0.409	
IR: inpatient rehabilitation; FuR: follow-up rehabilitation; N: number; N/A: not applicable;1χ2 test df=1, if N≥5, Fisher’s Exact Test if N<5;2only evaluated for employed persons,3only evaluated for smokers, FuR: no smokers within the group, IR: N=7. *Statistically significant differences between the two groups.

Rehabilitation goals and goal achievement

In both groups, the majority of rehabilitation patients set the goal of improving their health and performance, as well as reducing respiratory distress. Some goals were significantly more frequently mentioned by patients in IR: improving health status and performance, improvement of concentration, coping with illness and reduction of pain. The improvement of lung function and the reduction of medications, on the other hand, were mentioned more frequently in the FuR group. The goals named by the patients at the start of rehabilitation are shown in Figure 3.

Figure 3 —Rehabilitation goals.

With regard to achievement of goals, at the end of rehabilitation, the majority of the respondents stated that their shortness of breath had been alleviated and their performance and health status had improved. The improvement of health and the restoration of lung function was significantly more frequent for people in FuR. In addition, seven patients in the IR group and one person in the FuR group reported that they did not achieve any of the listed goals during rehabilitation. Table V shows the rehabilitation goals achieved by both groups.

Table V —Goals achieved during rehabilitation [percentage].

Rehabilitation goals	IR N.=170	FuR N.=62	P value1 groups	
Reducing breathlessness	72.4	75.8	0.599	
Increasing performance	72.4	67.7	0.493	
Improving health status	63.5	82.3	<0.01*	
Improving mobility	58.8	66.1	0.313	
Disease management	35.3	35.5	0.979	
Restoring ability to work	32.9	27.4	0.423	
Restoring lung function	23.5	54.8	<0.01*	
Increasing concentration	17.6	11.3	0.242	
Relieving pain	17.1	11.3	0.283	
Reducing anxiety	12.9	11.3	0.737	
Reducing medications	5.3	6.5	0.734	
No goal achieved	4.1	1.6	0.355	
IR: inpatient rehabilitation; FuR: follow-up rehabilitation;1χ2 test df=1. *Statistically significant differences between the two groups.

Satisfaction with the rehabilitation program was evaluated as good to excellent by 88.4% in the IR group and 98.4% in the FuR group (P<0.01). A total of 77.3% of the rehabilitees in the IR group and 93.7% in the FuR group rated their perceived rehabilitation success as good to excellent (P<0.01). All FuR patients and 85.9% of IR patients would recommend the rehabilitation program to their friends or family (P<0.01).

Rehabilitation aftercare

Overall, 40.5% of the rehabilitation patients at the end of IR and 50.8% of those in FuR felt prepared for the post-rehabilitation period. Only 29.5% of FuR patients and one-third of IR patients felt well prepared for their job.

In the year after rehabilitation, 64.1% of IR patients used rehabilitation aftercare, while only 48.8% of FuR patients took advantage of aftercare (P<0.01). No one used the psychological aftercare program Psy-RENA for follow-up care, and there was no statistically significant difference between the two groups with regard to the different therapies. Figure 4 shows the percentage of utilization of the aftercare offers for both groups.

Figure 4 —Rehabilitation aftercare.

Twelve months after rehabilitation, aftercare was rated as good to very good by 30.4% of those in IR and 43.2% of those in FuR (P=0.026). A total of 42.3% of the rehabilitees in the IR group and 23.6% of the individuals in the FuR group missed something during rehabilitation aftercare (P=0.015).

Discussion

In its call for action, the World Health Organization proposed rehabilitative and integrated care for people affected by Long COVID. Two out of four recommendations address rehabilitation: assessing the need for rehabilitation services, strengthening the health sector, and providing needs- and evidence-based treatment.37 Thus, the overall need for rehabilitation has increased with COVID-19, as has the need for research. This study aimed to investigate the health status and occupational situation of patients after FuR compared with those after IR. These findings are, however, primarily attributable to rehabilitative care in Germany and are mainly comparable with national samples.

The sociodemographics of the rehabilitation groups were similar to those in other epidemiological studies. Previous studies have shown that female sex is a risk factor for the development of Long COVID,3 which explains why 68% of IR patients were women. In contrast, men are more likely to have a severe or fatal course of COVID-19.38 Accordingly, there was a greater number of males in FuR.

Previous studies have shown improvements in subjective health during pulmonary rehabilitation after COVID-19,9, 11, 15, 18 and there is only one study with longitudinal data for people in IR which emerged from this study.39 In the observational study by Glöckl et al., patients with a severe or critical course of disease started the rehabilitation program with greater restrictions than rehabilitees with a mild or moderate course,15 whereas the participants in this sample showed no clear tendency at the start of rehabilitation. While FuR patients had greater limitations in participation and physical quality of life, IR patients felt more impaired by fatigue, anxiety and depression. This is consistent with another German study in which patients with a mild COVID-19 course had greater impairment in fatigue, anxiety and depression than those with a severe course.18 In addition, subjective health showed a different course during rehabilitation and follow-up between both groups. While the IR patients mainly achieved medium to large effects during rehabilitation, FuR patients had only small to medium effects in equal proportions. Other studies have shown stronger improvements during rehabilitation for patients with a severe course,15 which was not confirmed by the data collected in this study. Overall, patients in both groups started rehabilitation with similar levels of limitation, although there were differences in some outcomes. During follow-up, impairment increased in both groups but clearly under the level at admission. However, there are currently no randomized controlled trials with sufficient numbers of cases comparing multidisciplinary rehabilitation with usual care. This provides no certainty of whether the effects are due to rehabilitation or to natural regeneration. Current evidence suggests that rehabilitation after hospitalization is beneficial compared with usual care.40 There were also parallels between health improvements and rehabilitation therapies. Almost all participants of both groups used endurance training or respiratory physiotherapy, which was reflected in a reduction in CAT-score and dyspnea. Depression, anxiety and stress were particularly reduced during IR, where psychological support and relaxation exercises were used significantly more often. These observations provide evidence that the therapies during rehabilitation had an impact on the appropriate health restrictions.

With regard to present symptoms, IR patients reported more neurocognitive complaints at the start of rehabilitation, which improved significantly over time. In contrast, FuR patients showed an increase in this symptom cluster, e.g., 6.6% of the patients had word-finding difficulties at baseline, while 27.4% reported this symptom at follow-up (P<0.01). Other symptoms also increased, although the majority were not statistically significant (joint pain, concentration problems, short-term memory problems). Because the neurocognitive symptoms were not pronounced in FuR patients at the start of rehabilitation, rehabilitation therapy was not geared towards this. As FuR patients started rehabilitation on average one month after infection, whereas IR patients started rehabilitation five months after infection, it is possible that neurocognitive symptoms developed over time as a normal course of Long COVID. The increasing health impairments could not be conclusively explained, but the survey showed that in both groups, only 49% and 64% received rehabilitation aftercare. Furthermore, as there was no control group without rehabilitation, it could not be ruled out that limitations equally increased over time without rehabilitation.

According to other research studies, half of the rehabilitees in FuR who have been treated in the hospital are still at risk of developing persistent symptoms for at least four months after infection.41 This estimate should be considered in light of the fact that our respondents received timely care in a rehabilitation facility. However, some of these patients develop symptoms similar to the initial condition of IR patients. Furthermore, as a result of intensive care unit (ICU) stay, patients can develop post-intensive care syndrome (PICS), which is characterized by mental (anxiety, posttraumatic stress disorder, depression), cognitive (e.g., executive function, memory, attention) and physical impairments (pulmonary, neuromuscular and physical function).42 Long-term quality of life, daily functioning, and physical and neuropsychiatric impairment may be reduced in association with PICS. To date, only one study has been published that interviewed 61 COVID-19 patients after ICU admission. Fifty percent of them suffered from PICS six months after ICU admission.43 This is in line with previous studies on other diseases that showed that half of the patients developed PICS one year after ICU admission.44 Among FuR patients in this study, 63% had been treated in the ICU and potentially developed this syndrome. However, Long COVID and PICS show overlapping symptoms such as fatigue, depression, sleep disturbance, shortness of breath, pain and cognitive impairment.45 Consequently, it is difficult to make a clear distinction between the two syndromes.46

Patients in this sample reported different rehabilitation goals, depending on their symptoms and impairments. In the group with predominantly mild COVID-19 progression, fatigue and neurocognitive symptoms were more pronounced, so it is not surprising that increasing performance and improving concentration were more frequently pursued as rehabilitation goals in this group. In contrast, FuR patients more often reported dyspnea and cough. Almost three-quarters of these rehabilitation patients wanted to restore their lung function during rehabilitation. Further examination of the therapy content showed that both the goals and the existing limitations of the rehabilitees were considered. While FuR patients were more likely to participate in respiratory muscle training, IR patients more often took part in relaxation exercises, psychological support, physiotherapy and creative therapy. To date, it is not known from other studies in which way therapy programs differ between COVID-19 rehabilitation groups.15 Most studies on Long COVID have either been conducted in the field of pulmonary rehabilitation,15, 18 organized across several departments11 or taken place in neurology, psychosomatics or cardiology.7 In an ongoing comparative study, Long COVID rehabilitation is being implemented in different disciplines to gain more detailed insights into impairments and therapy content.47 Today, the general recommendation is to treat Long COVID with a symptom-oriented approach in rehabilitation.7

At the end of rehabilitation, 69% of participants did not achieve their rehabilitation goal of increasing their subjective perceived ability to work to a sufficient level. Despite this estimation, the majority of rehabilitation patients (88%) managed their return to work in the year after rehabilitation. Nevertheless, this positive result must be seen in the wider context of the fact that rehabilitation patients still perceived their ability to work to be reduced by 30-40%. Comparative data on the RTW of COVID-19 rehabilitees are limited, as most studies asked about work ability at the end of rehabilitation but not in a follow-up survey. These studies report that only 27% to 53% of rehabilitees are able to work at the end of rehabilitation.11, 30, 48 In our group, 68% were actually discharged unable to work, but this only meant a delay for a few weeks in their return. In the end, the vast majority returned to work one to five weeks after rehabilitation. This is in line with the findings of a systematic review of RTW with Long COVID, which concluded that besides other factors the rate of RTW depends on the time of the survey.49 The time between rehabilitation and the first day at work was significantly longer for FuR patients. Other studies have also shown a later return to work after hospitalization among COVID-19 patients.49 This may be related to a not yet achieved work ability among FuR patients at the end of rehabilitation. At the same time, the inability to work before rehabilitation in the group of IR patients was significantly longer, eleven weeks, so extrinsic motives (fear of job loss, paid sick leave, etc.) may also have played a role in their earlier return to work. Generally, Long COVID can lead to longer absences from work, which was shown by an analysis from a German health insurance company: people diagnosed with Long COVID were absent from work for an average of 105 days, compared to 14.5 days for insured individuals with other conditions.16

The perceived success of rehabilitation, satisfaction with rehabilitation and aftercare and willingness to recommend rehabilitation were higher among FuR patients. This is consistent with other studies in which people with a severe course of disease also perceived their rehabilitation as more effective than those with a mild COVID-19 course.18 A possible explanation for this is that FuR participants more frequently had pulmonary symptoms, which made it easier to treat them in pulmonary rehabilitation, whereas IR patients had a much wider range of symptoms, including neurological symptoms. Unexpectedly, rehabilitation aftercare was also rated more positively by FuR patients, even though half of the patients did not receive any aftercare. Regarding the reasons for not using rehabilitation aftercare, the most common reason given by FuR patients was that they did not need any aftercare, compared to IR patients who explained that there was no provision at home and that they had not received a recommendation from the clinic. Nevertheless, rehabilitation aftercare is necessary because of symptoms and limitations that obviously persist after rehabilitation.11 The requirements and needs in rehabilitation aftercare, especially for IR, do not seem to have been fully met.

Limitations of the study

The many reported results must be interpreted with the following limitations. Although the dropout analysis showed no differences between responders and dropouts for most outcomes, the FuR respondents included a higher proportion of people with a severe or critical COVID-19 disease. Maybe the importance of participating in the study was not as high for people with a milder course of the disease. Despite this difference in the COVID-19 course, the different scales describing the subjective state of health were comparable, indicating a similar level of health impairment. Although a small degree of uncertainty remains, it can be assumed that the data are not biased by dropouts.

In addition, the presented results have only limited applicability to the care of Long COVID in other countries and apply primarily to the rehabilitation care established in the German healthcare system. In many countries, this part of healthcare is not provided at all or is organised in a different way.

As there was no COVID-19 comparison group because of ethical reasons, it was not possible to determine whether the improvements were due to rehabilitation or to natural regeneration. However, initial small RCTs50 and comparative analyses40 show that rehabilitation improves the health status of people with Long COVID. Prior to medical rehabilitation, health impairments were assessed by a social medicine expert and had restrictions been present for months in the case of IR. The statistical changes measured during rehabilitation with medium to large ES can be attributed at least in part to the therapy.

Despite these limitations this investigation provides relevant evidence for future research, randomized controlled trials and clinical practice.

Conclusions

In medical rehabilitation after COVID-19, it is indispensable to distinguish between FuR and IR patients, as they not only differ socio-demographically but also pursue different goals in rehabilitation due to their health impairments. For IR patients whose fatigue symptoms are severe, adjustments in terms of interdisciplinary cooperation and therapy are necessary to treat this group of patients in pulmonary rehabilitation according to their needs. It is important to continue to follow-up FuR patients after rehabilitation to identify Long COVID syndrome or PICS at an early stage and to initiate symptom-driven and, if possible, interprofessional treatment. The rehabilitation aftercare must also be in line with the individual needs.

Supplementary Digital Material 1

Supplementary Table I

Results of dropout analysis.

Supplementary Digital Material 2

Supplementary Table II

Subjective health scales over time.

Supplementary Digital Material 3

Supplementary Table III

Prevalence and course of symptoms.

Acknowledgements

We would like to thank all study participants for completing the questionnaires several times. Furthermore, we thank Ostseeklinik Schönberg-Holm, Reha-Zentrum Schömberg, MEDIAN Klinik Heiligendamm and MEDIAN Klinik Flechtingen for their commitment to this study and organizational support during recruitment and the written survey.

Conflicts of interest: The authors certify that there is no conflict of interest with any financial organization regarding the material discussed in the manuscript.

Funding: This research was funded by the German Pension Insurance Association, grant number 0421/40-64-50-74. The authors report no involvement in the research by the sponsor that could have influenced the outcome of this work.
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