The total number of treated cases of COVID-19 in the Novoiavorivsk District Hospital named after Yuri Lypa for the period from July 1, 2021, to July 1, 2022, was 1980 patients aged 18–92, including 1229 (62%) females and 851 (38%) males. Table 1 reflects the number of distribution patients with COVID-19 during the time of study for which response rates varied between 73.3% and 26.7% for 2021 and 2022, respectively.

The number of patients who died in the hospital was 238 (11%). Despite women being treated in our hospital more frequently, the male patients (65%) died further often.

In the beginning, we included 620 patients of both sexes aged 28–70 years (the average age was 42–45). About 70% of these patients were dependent on oxygen support during treatment. Signs of long COVID regarding the guidelines and criteria of exclusion in the study group were found in 332 out of 620 examinees, which was 53.5%. Among them are 230 (69.2%) females and 102 (30.7%) males.

The follow-up time of participants was from 4 to 50 weeks. The general information, including age, sex, body mass index (BMI), diet, marital, educational, and social status, cumulative duration of sick leave, as well as lifestyle factors (sedentary behavior, moderate or vigorous-intensive activity), grades of physical activity and smoking status of participants in the study group of long COVID are presented in Table 2.

The long COVID was more often diagnosed in patients with increased BMI (61%) in comparison to those with normal or decreased BMI, and who had a sedentary lifestyle and/or low physical activity.

During recognition of ANS status, the signs of sympathetic hyperactivity dysautonomia were in 40% of people in the group aged 18–27 years. Most of them (80%) had a sedentary lifestyle and/ or low physical activity.

An interesting fact was that 315 examinees (95%) of the total number of patients with long COVID had ≥ 3 somatic or mental health symptoms. The symptoms we observed in our patients can be divided into several clusters: (1) physical; (2) neurocognitive; (3) pulmonary; (4) pain related as well. The core symptoms for physical cluster were fatigue and hair loss; for neurocognitive—brain fog, anosmia, and fear; for pulmonary—dyspnea; for pain-related—muscular pain. The distribution and period differences of these core symptoms are presented in Figs. 1 and 2. The symptoms were more severe in patients who were hospitalized during COVID-19 treatment (Fig. 1) in comparison to non-hospitalized patients during acute infection of SARS-CoV-2 (Fig. 2). The most common long COVID symptoms (about or more than 50% of total cases) with duration more than 2 weeks were anosmia, muscular pain, and hair loss among hospitalized patients during acute infection than in those with hair loss among non-hospitalized patients. Additional common symptoms were problems with concentration and paying attention (25%), trouble with memory and focus (20%), thoughts that can be described as sluggish or fuzzy (20%), and executive functioning problems (20%). There were recognized signs of depression and fear too. Among long COVID study groups’ participants were patients with post-traumatic stress disorder (6%), and one patient had the debut of schizophrenia.

Core symptoms period differences (less than 2 weeks and more than 2 weeks) in long COVID patients who were hospitalized during COVID-2019. Data are in %

Core symptoms period differences (less than 2 weeks and more than 2 weeks) in long COVID patients who were non-hospitalized during COVID-2019. Data are in %

Laboratory findings in the study group’s participants during COVID-19 illness reflect Fig. 3. They were related to increasing D-dimers, C-reactive proteins, fibrinogen levels, changes in white blood cells (WBC, leukopenia at the beginning of the disease, and leukocytosis on day 8–12 of the disease in 84%), increased ESR at the 10th day of the beginning of the disease (69%), increased hematocrit level in patients, who depended of oxygen more than 7 days (81%).

Frequencies of laboratory findings in participants with long COVID during their COVID-19 illness. Data in %