1. Introduction
The World Health Organization defines long COVID as a condition occurring in patients with a history of probable or confirmed SARS-CoV-2 infection that typically develops 3 months after the onset of symptoms, persists for at least 2 months, and cannot be explained by alternative diagnoses [
1]. In long COVID patients, various symptoms may persist, including those affecting the vascular system, respiratory system, musculoskeletal system, gastrointestinal tract, urinary system, and nervous system [
1,
2]. Neurological symptoms arise from damage to the central and peripheral nervous systems, which is why diverse neurological symptoms may be observed in COVID-19 survivors. Among these, the most frequently reported are fatigue, sleep disturbances, headaches, anxiety, depression, dizziness, numbness, ageusia, altered taste, postural instability, memory loss, concentration difficulties, and vision impairment. The prevalence of symptoms varies depending on the report. Nevertheless, in long COVID patients, fatigue, sleep disorders, and headaches are the most commonly observed symptoms [
1,
2,
3,
4,
5,
6].
The exact pathomechanism of persistent neurological symptoms in long COVID patients is still debated. It is postulated that coagulopathy, resulting from inflammation, cellular damage, and vascular dysfunction, leads to insufficient tissue oxygenation and may thus contribute to long-lasting symptoms in COVID-19 survivors [
5,
7,
8]. Other factors that might impact prolonged neurological symptoms include thrombosis and disruption of the blood–brain barrier [
5,
9]. Moreover, chronic inflammation is also linked to long-term symptoms [
5,
7,
8]. Grisanti et al. [
9] suggest that neuropathies are inflammation-dependent, as inflammation may be a manifestation of nerve damage caused by the SARS-CoV-2 virus or an autoimmune reaction. Angiotensin-converting enzyme 2 receptors also play a significant role in the neurological sequelae of COVID-19. Since these receptors are distributed in different parts of the central nervous system, particularly in the brain stem, the presence of certain symptoms may be associated with the involvement of specific sites rich in these receptors [
3]. Additionally, since neurons have limited regenerative ability, this may also contribute to the long-term neurological symptoms in individuals who have recovered from COVID-19 [
2]. Furthermore, some reports also indicate disturbances in the brain glymphatic system] [
10] and autonomic dysfunction [
11] as factors contributing to persistent neurological symptoms in long COVID patients. Considering the various mechanisms determining the neurological sequelae of COVID-19, patients may exhibit various symptoms; therefore, a complex approach to alleviate them is required.
Long COVID is a reason for the public health and economic burden, particularly among elderly people [
12]. Mirin [
13] estimated that in the USA, the annual medical costs associated with long COVID range from USD 43 billion to USD 172 billion. Therefore, different treatment strategies have been implemented to reduce the severity of persistent COVID-19 symptoms, including rehabilitation [
2,
10], exercise [] [
14,
15], dietary supplements [
7,
16], pharmacotherapy [
2,
17,
18,
19], aromatherapy [
20], brain stimulation [
21], and hyperbaric oxygen therapy [
22]. Thurner et al. [
23] suggest that neurocognitive training and individual psychotherapy should also be implemented, as patients with long COVID experience not only physical symptoms. In Poland, the costs of post-COVID rehabilitation were funded by public resources, in accordance with a decree of the president of the National Health Fund (63/2021/DSOZ). Patients were qualified for the post-COVID rehabilitation program based on a valid referral provided by a health insurance doctor.
It is suggested that balneotherapy may effectively mitigate long COVID symptoms [
24]. Health resort treatment is a complex therapy, not only due to the application of balneological factors (mineral waters, mud therapy, gas therapies) and climatotherapy but also because of the use of various procedures, including hydrotherapy, massage, exercise, and physical medicine modalities. Other key elements of this treatment approach are health education, psychotherapy, and diet [
24,
25,
26,
27,
28,
29]. Health resort treatment can be carried out in various environments, such as seaside, mountain, upland, and lowland areas [
30,
31], where the natural surroundings promote healing. Regardless of the sanatorium’s location, recreation, cultural, and social aspects also influence patients during the treatment course [
29]. Treatment applied in sanatoria has been shown to reduce inflammation, ease pain, modulate the immune system, modify hormone activity, improve blood flow and hemorheology, alter oxidative status, and influence the autonomic nervous system [
32,
33,
34,
35,
36]. Considering hypotheses explaining persistent COVID-19 symptoms, complex health resort treatment may be effective [
5,
9,
10,
11]. Health resort treatment has few side effects when the approach is personalized [
37]. Compared to pharmacotherapy for long COVID, it may be more favorable due to its multidirectional action, as the heterogeneity of post-COVID syndrome tends to be a limitation of pharmacotherapy [
2].
Until now, few studies have evaluated the effects of health resort treatment in post-COVID patients [
38,
39,
40,
41]. However, Costantino et al. [
41] have proven that spa therapy reduced anxiety, depression, and stress, as well as improved sleep quality in patients with a history of COVID-19. García-López et al. [
33] reported that balneotherapy improves depression, while Masiero et al. [
26] postulated that it may also mitigate anxiety and mental stress. Nevertheless, no study has assessed the effects of health resort treatment on the severity of concentration and memory disorders, dizziness, and paresthesia. This is why our study may be informative and help fill a gap in knowledge. Considering the favorable effect of balneotherapy, we also decided to verify its superiority over non-balneological approaches in mitigating long COVID neuropsychiatric symptoms during treatment in a sanatorium.
This study had three aims. The first was to assess the severity of concentration disorders, memory disorders, headaches, dizziness, sleep disorders, paresthesia, depression, and anxiety in long COVID-19 patients who qualified for health resort treatment. The second was to assess the effectiveness of the complex treatment applied in the health resort to this group of patients. The third was to compare the efficacy of treatment based on the application of balneological factors.
2. Materials and Methods
2.1. Eligibility Criteria
The inclusion criterion was a complete medical record, including demographic data, medical history, description of the treatment course, and levels of concentration and memory disorders, headaches, dizziness, sleep disorders, paresthesia, depression, and anxiety.
The following exclusion criteria were set: age above 80 years, neuropsychiatric disorders (multiple sclerosis, post-stroke syndrome, Parkinson’s disease, epilepsy, depression), cardiovascular diseases (coronary artery disease, heart failure, myocardial infarction history, percutaneous coronary interventions and/or coronary artery bypass grafting history, endarterectomy history, pacemaker implantation, atrioventricular and/or bundle of His blocks, atrial fibrillation, peripheral artery disease), respiratory system disorders (chronic obstructive pulmonary disease, emphysema, pneumoconiosis, asthma), rheumatic diseases (rheumatoid arthritis, ankylosing spondylitis), cancer, lower limb amputations, blindness, Lyme disease, and inability to undertake general development exercises. These conditions were considered confounders that could impact the study results and diminish the study’s reliability.
2.2. Data Collection
We reviewed the data on 239 patients undergoing health resort treatment for long COVID at the Gwarek Rehabilitation Hospital and Sanatorium in Goczałkowice-Zdrój (Poland) in 2021. The town is situated in the Oświęcim Valley, making it a lowland resort with an area of 4864 ha. Health resort status was awarded to the town in 2016 [
42,
43]. Evaluation of long COVID symptom severity before and after treatment was required by the Polish post-COVID rehabilitation program. The data were not originally collected for scientific purposes. After obtaining the positive opinion of the authorities of the Gwarek Rehabilitation Hospital and Sanatorium, patient data were anonymized and then reviewed. Therefore, no informed consent was required. Medical records were reviewed between March and May 2024. The Bioethical Committee of the Medical University of Silesia in Katowice stated that this project did not require its opinion (decision BNW/NWN/0052/KB/238/23).
2.3. Subjects
After considering the exclusion criteria, 150 medical histories were included in the next stage of review. Due to incomplete data, 30 medical records of patients undergoing health resort treatment were excluded. In the final stage, medical records of 120 patients were analyzed (
Figure 1).
2.4. Treatment Course
The treatment course was individually tailored based on the analysis of clinical symptoms during the examination upon admission. The treatment was not standardized, and varied among patients depending on their condition and needs. Nevertheless, according to the Polish post-COVID rehabilitation program, each patient was required to attend at least four procedures each day during treatment. In total, the treatment course involved performing 96 procedures during the stay at the sanatorium. The treatment was complex due to the application of various methods, including balneotherapy, general developmental and respiratory exercises, physical medicine modalities, and health education. Respiratory exercises aimed to relax chest muscles, improve diaphragmatic breathing, activate the lower ribs, and facilitate prolonged exhalation. Meanwhile, general developmental exercises were designed to train dynamics, endurance, balance, coordination, and muscle strength. A physiotherapist supervised all exercises. Each patient underwent a routine control examination after seven days of treatment to verify a favorable reaction to the applied treatment and to exclude side effects. All patients attended health education sessions aimed at promoting a healthy lifestyle and supporting recovery from addiction, if applicable. Moreover, all patients also received psychological support. After completing the treatment, patients were discharged. The treatment duration varied, as the rules of the Polish post-COVID rehabilitation program stipulated an intervention of 2 to 6 weeks.
2.5. Symptom Severity Evaluation
Prior to the long COVID symptom severity assessment, patients were instructed on how to use the numeric rating scale. Participants were informed that they should assess the severity of symptoms at the time of evaluation. Additionally, patients were instructed to state the number that most reliably represented the severity of particular symptoms, with the assumption that 0 indicated “no symptoms” and 10 represented “the most severe symptoms imaginable.” We adopted the following method of interpretation: 0—no symptoms; 1–3 points for mild symptoms, 4–7 points for moderate symptoms, and 8–10 points for severe symptoms.
2.6. Statistical Analysis
Statistical analysis was performed with STATISICA 13 PL software. The effect size was calculated using G Power 3.1.94 software. With the assumption of a sample size of 120, α = 0.05, and statistical power (1-β error probability) = 0.95, the effect size was established as ƒ = 0.309. Data normalcy distribution was checked with the Shapiro–Wilk test. Intragroup comparisons were performed using the Wilcoxon signed-rank test. Intergroup comparisons (between genders and groups of patients depending on application of balneological factors) were carried out with the Mann–Whitney U test. Moreover, we calculated delta values (∆), expressed as the difference between pre- and post-treatment assessments, to establish the magnitude of symptom changes. The statistical significance level was set at p < 0.05.
3. Results
Medical records of 120 people with long COVID (69 women and 51 men) aged 42–79 years (mean age: 64.21 years ± 8.67 years) were analyzed. The patients’ mean body mass was 85.91 kg ± 15.27 kg, mean body height was 1.67 m ± 0.09 m, and mean body mass index was 30.71 kg/m
2 ± 5.09 kg/m
2. In the reviewed individuals, mean systolic blood pressure was 139.63 mmHg ± 13.34 mmHg, and diastolic blood pressure was 80.08 mmHg ± 7.55 mmHg, measured upon admission. Treatment duration ranged from 17 to 47 days (mean treatment duration: 24.44 days ± 6.24 days). Patients’ characteristics are presented in
Table 1.
In patients who qualified for the health resort treatment, hypertension was the most common coexisting disease (58.33%, n = 70). In hypertensive patients, mean systolic blood pressure was 141.8 mmHg ± 13.12 mmHg and diastolic blood pressure was 80.27 mmHg ± 8.16 mmHg upon admission. Type 2 diabetes mellitus was coexisting in 18.33% of the individuals (n = 22). In diabetic patients, mean glycemia was 120.42 mg/dl ± 17.27 mg/dL. Degenerative joint disease was noted in 21.67% of patients (n = 26). Hypothyroidism was diagnosed in 12.5% of patients (n = 15). Gout was observed less frequently (3.33% of patients, n = 4). Only one man was diagnosed with benign prostatic hyperplasia.
In patients undergoing health resort treatment for long COVID, the most frequently applied modality was pneumatic massage (65.83%,
n = 79). Among physical medicine modalities, low-level laser therapy (60%,
n = 72) was the most frequently administered. Water therapies were applied less frequently. Mud therapy was prescribed to 13.33% of patients (
n = 16). Only six individuals (5%) underwent ultrasound therapy (
Table 2).
Most long COVID patients reported that persistent neuropsychiatric COVID-19 symptoms were of mild intensity. Only 4% of individuals were affected by severe concentration and memory disorders, as well as paresthesia (
Table 3).
During the pre-treatment assessment, women reported greater intensity of persistent neuropsychiatric COVID-19 symptoms. Upon admission, women had approximately 16% more concentration problems and about 39% more memory disorders. Depression severity was about 37% higher in women who qualified for health resort treatment compared to men. Additionally, women experienced more headaches and dizziness, with an increase of about 50% and 58%, respectively, compared to men. After treatment at the health resort, the severity of symptoms did not differ between genders. However, the health resort treatment led to a significant reduction in all persistent COVID-19 symptoms. In the entire group of patients, the highest decrease in symptom severity was noted for dizziness (approximately 75% reduction), while the lowest decrease was observed for memory disorders (approximately 63% reduction). After treatment, women reported the greatest reduction in dizziness (approximately 79%), paresthesia (approximately 73%), and depression (approximately 71%). Memory disorders showed the lowest improvement in women (approximately 64%). In men, the treatment led to significant improvements in anxiety (approximately 82% reduction), paresthesia (approximately 77% reduction), and headache (approximately 77% reduction). The lowest effectiveness of the treatment was observed in sleep disorders (approximately 60% improvement) (
Table 4). A comparison of the magnitude of symptom changes revealed that in women, ∆memory disorders and ∆dizziness were approximately 44% and 65% greater than in men (
Table 5).
The study group was divided into two subgroups based on the use of balneological factors during treatment at the sanatorium. Group I (
n = 70) consisted of individuals treated with balneological factors (mud therapy, water therapies). Group II (
n = 50) comprised individuals who were not exposed to natural healing resources. The only difference between the groups was diastolic blood pressure at admission; it was 3% higher in group II. The characteristics of patients included in groups I and II are presented in
Table 6.
Before treatment, in group I, the severity of concentration disorders, paresthesia, and depression was significantly higher than in group II. At baseline, paresthesia was approximately 43% more severe in group I than in group II, while concentration disorders were approximately 38% more severe, and depression was about 27% more severe. After treatment, the severity of symptoms did not differ between the groups. In patients who received balneological treatments, the severity of all symptoms improved. The greatest reductions were noted in dizziness (approximately 77%), paresthesia (approximately 74%), and anxiety (approximately 72%). In group II, a similar pattern of symptom severity reductions was observed. The greatest improvement was observed in paresthesia (approximately 74%), headache (approximately 74%), and dizziness (approximately 73%) (
Table 7).
In patients assigned to Group I, the magnitude of symptom changes was greater than in those not treated with balneological factors. The change in concentration disorders (∆concentration disorders) was approximately 41% greater in Group I than in Group II. The change in memory disorders (∆memory disorders) was approximately 36% greater in Group I compared to patients in Group II. The largest difference between the groups was observed in ∆paresthesia (approximately 44% difference). The smallest difference between the groups was noted in ∆anxiety (approximately 34%) (
Table 8).