Effect of post COVID-19 on body composition, physical fitness, sleep quality and quality of life among young adults: a cross-sectional study of matched pairs

Introduction

Coronavirus disease 2019 (COVID-19) is a disease caused by exposure to the severe acute respiratory syndrome coronavirus 2 (SAR-COV-2), which began to spread in China since 2019. The number of infections increased in many countries. Therefore, the World Health Organization (WHO) declared an epidemic in March 2020. As of April 13, 2024, more than 704 million people worldwide have been infected and more than 7 million have died from COVID-19. Thailand has the 33^rd highest number of infected people in the world, with a total of more than 4 million infected and more than 30,000 people who have died from COVID-19 (Worldometers, 2024).

When the body is infected with SAR-COV-2, it causes lung tissue inflammation. These include interstitial pneumonia and respiratory distress syndrome, which cause organs such as the heart, lungs, brain and nervous system to fail (Zhou et al., 2020). Furthermore, it affects mental health (anxiety and depression), disturbs sleep and the musculoskeletal system (pain and muscle weakness), and causes fatigue (WHO, 2020).

Recent studies have shown that some patients may develop complications from infection, and 11 to 24 percent of patients’ symptoms may last longer than 3 months after exposure (Cirulli et al., 2020; Ding et al., 2020; WHO, 2020). Therefore, it may reduce physical fitness and quality of life. In addition, after the COVID-19 infection has disappeared, patients may still have other symptoms. Symptoms are usually found 4 weeks or more after being infected, also known as the long Covid condition (Ladds et al., 2020). This could be a new symptom or a residual effect after treatment; and symptoms such as hypoxia, shortness of breath or dyspnea, decreased ability to work (reduced ability to work) (Bryson, 2021; Santus et al., 2020), and fatigue (Shanbehzadeh et al., 2021) may persist for more than or equal to 12 weeks. Factors affected by fatigue consist of conditional factors and physiological factors. The conditional factors include job characteristics, environment, and individual physical and mental abilities. The physiological factors include central factors (levels of neurotransmitters, neuron activation, inflammation, and multiple sclerosis), psychological factors (stress, anxiety, depression, and fear) and peripheral factors (skeletal muscle) (Rudroff et al., 2020).

Previous literature have reported that physical fitness and quality of life were studied in patients with COVID-19, but very few studied the effects of post COVID-19 infection (Rudroff et al., 2020). Factors affecting the symptoms of post COVID-19 patients include high blood pressure, obesity, mental health condition (Tenforde et al., 2020), age, associated comorbidities, severity of COVID-19 symptoms, and severity of COVID-19 infection (Sharma, Bharti & Garg, 2022). Therefore, this study aimed to examine the impact of COVID-19 infection on body composition, physical fitness and quality of life in Walailak University students who had recovered from COVID-19 infection in order to provide a guideline to raise awareness on preventative measures and physical rehabilitation after COVID-19 infection.

Materials and Methods

Participants and setting

This study is a cross-sectional study (Observational study: matched case-control). Data was collected from July to September 2022 at the Physical Therapy Research Laboratory, Walailak University. Walailak University granted ethical approval to carry out the study within its facilities (Ethical Application Ref: WUEC-22-204-01).

The study objectives, research process, and benefits to be gained from participating in the study were explained to all volunteers. Participants signed a consent form to participate in the study, and selection of participants was according to the inclusion and exclusion criteria. Data was collected from the research project participants who met the inclusion criteria (Fig. 1).

The volunteers interested in participating in the study were screened, and those who could not understand the questionnaire and had peripheral blood oxygen saturation (SpO₂) <95% were excluded from the study. The inclusion criteria of each group were as follows:

Post COVID-19 group: This group included Walailak University students, both male and female with normal range body mass index (BMI) from 18.5 to 22.9 kg/m² (Supadanaison, Panklang & Seechumsang, 2019), who had been diagnosed with COVID-19 and had recovered or completed the quarantine period within 1–3 months after being infected. At least one symptom should remain. The average number of days since the COVID-19 infection was 50 days and ranged from 30 to 119 days.

Non COVID-19 group: This group included Walailak University students, both male and female with normal range BMI, who have never been diagnosed with COVID-19 infection.

Results

Out of a total of 267 volunteers, 128 had been exposed to COVID-19, representing 47.9%. Out of the 128 that had been exposed, 36 post COVID-19 patients (28.1%) had passed the inclusion criteria, whereas 92 were excluded due to asymptomatic COVID-19. Of the 72 participants in the study, 36 had never been infected with COVID-19 and 36 had been infected with COVID-19. Most of the participants were female (80.6%), with light physical activity levels (75%), and non-smokers (97.2%). In addition, 69.4% of the post COVID-19 group and 63.9% of the non COVID-19 group did not get enough sleep during the night. Regarding quarantine as a high-risk group, 75% of the post COVID-19 group and 58.3% of the non COVID-19 group had been quarantined as a high-risk group. Additionally, there was no statistically significant difference between the two groups, as shown in Table 1.

Discussion

The purpose of this study was to determine the impact of COVID-19 on body composition, physical fitness, sleep quality and quality of life. There was no statistically significant difference in all parameters of body composition (body fat, muscle mass, visceral fat, lean body mass and total body water) between the post COVID-19 and non COVID-19 groups, contradicting the previous studies that post COVID-19 group had statistically significant increase in body fat (Atieh et al., 2024; Peball et al., 2024) and decrease in muscle mass (Montes-Ibarra et al., 2023). This might be because the previous study had recruited participants who had been infected for more than 3 months, but the participants of the post COVID-19 group in this study had been infected for less than 3 months (average 50 days). Therefore, that the long duration after infection might have influenced the change in body composition. It might be interesting to follow up with the post COVID-19 group for more than 3 months. Furthermore, this might be attributable to the specific strain of SARS-CoV-2. During the data collection period, the dominant SARS-CoV-2 strains circulating in Thailand were primarily from the Omicron variant, particularly subvariants BA.1 and BA.2. These subvariants generally cause milder illness and less frequent loss of taste and smell compared to earlier variants like Delta (WHO, 2024). However, this study did not record the SARS-CoV-2 strain, so future research should identify the strain to better understand its impact on the outcomes.

The number of times to get up and sit for 1 min was not significantly different between the post COVID-19 and non COVID-19 groups. The post COVID-19 group had a greater decrease in blood oxygen saturation (SpO₂) after the 1MSTS than the non COVID-19 group. SpO₂ was measured using pulse oximetry, which provides a convenient, noninvasive method to measure blood oxygen saturation continuously. It can also help to eliminate medical errors. Pulse oximetry has a sensitivity of 92% and a specificity of 90% (Hafen & Sharma, 2022). Among the post COVID-19 group, pneumonia developed during the acute stage of infection (Peter et al., 2020) and decreased lung function due to a change in the structure of the lungs. It was found that lung elasticity was reduced by post-inflammatory fibrosis resulting in an uneven distribution of capillaries (Rana et al., 2021), causing breathing difficulties so that the exchange of oxygen in the blood was reduced. However, the difference was not clinically significant for detecting exercise-induced desaturation. A decrease in oxygen saturation of three percentage points or more during the test was considered clinically significant for detecting exercise-induced desaturation (Briand et al., 2018).

In addition, there was a statistically significant difference in the respiratory rate (p < 0.05) after the 1-min sit-to stand test, with those who had post COVID-19 showing a higher change in respiratory rate compared to those who had not been exposed to COVID-19. The respiratory rate is a specific and early indicator of physiological conditions like hypoxia and hypercapnia, highlighting its importance in identifying patient deterioration and prompting timely intervention. This is because dyspnea is a common residual symptom after exposure to COVID-19 (Nalbandian et al., 2021), even in mild cases. This was consistent with a previous study of hyperventilation in patients who had been exposed to COVID-19 with mild symptoms, and it was found that patients who had been exposed to COVID-19 had increased breathing rate and decreased ability to exercise during cardiopulmonary function tests (Motiejunaite et al., 2020).

From this study, it was found that there was no difference in hand grip strength between the post COVID-19 and non COVID-19 groups. This might be due to the participants’ symptoms at the time of exposure to COVID-19 were mild or classified as a green patient group. This contradicted a study by Tanrıverdi et al. (2021) who investigated physical fitness in people who had been exposed to COVID-19 with mild and moderate symptoms, and it was found that the group with mild symptoms had a slight decrease in muscle strength compared to the moderate group. The hand grip strength of both groups in this study was found to be moderate and there was only a 0.02 between-group difference, which was lower than the minimal clinically important difference (MCID = 0.04–0.7) (Bohannon, 2019).

There was a statistically significant difference in sleep quality between the post COVID-19 and non COVID-19 groups (p < 0.05). The non COVID-19 group had better sleep quality than the post COVID-19 group. This could be related to COVID-19 exposure, which impacted breathing difficulties and anxiety. Patients who had to be quarantined and separated from their family members could experience greater anxiety (Souza et al., 2021). According to a previous study, tension and depression were associated with poor sleep quality. In addition, insufficient sleep might have negative effects on the body such as fatigue, palpitations, irritability, headache (Ingram, Maciejewski & Hand, 2020) and stress (Mekhael et al., 2022).

This study found that quality of life had no significant difference between the post COVID-19 and non COVID-19 groups (p > 0.05). This could be because the study used a matched-pair design, where individuals with similar levels of physical activity were paired together. As a result, this pairing might lead to no noticeable differences in the quality of life between the two groups using EuroQol-5D-5L.

This study had several limitations. First, body composition can vary between genders; thus, future research should consider including only one gender to avoid this variability. Second, anxiety, depression and drug use may influence sleep quality and quality of life; therefore, further study should either collect information on or exclude cases with other factors that might affect sleep quality and quality of life. Third, this study recruited participants who had been diagnosed with COVID-19 and had recovered or completed the quarantine period within 1–3 months after being infected. Given that the post COVID-19 or long Covid condition is defined as the period extending beyond 1 month after COVID-19 infection, further study should include participants who took more than 3 months to recover or complete their quarantine period to provide a comprehensive analysis of the long-term effects of the novel coronavirus. Fourth, the non COVID-19 group was not confirmed for COVID-19 status through PCR or antibody tests in this study. There is a possibility that some asymptomatic individuals with COVID-19 were included in the control group. Future research should include verification of COVID-19 status using PCR or antibody tests to ensure the integrity of the control group. Fifth, this study did not account for other confounding factors such as chronic diseases and vaccination status when matching groups, which may impact the reliability of the comparisons made. Future studies should include these additional confounding factors when matching groups to enhance the accuracy of the results. Sixth, this study may have a small sample size. To increase the test’s power, future research should be conducted with a larger sample size. Lastly, the study was a cross-sectional study that did not establish a true cause-and-effect relationship. Further studies should follow up with the participants over time to establish a causal relationship.

Conclusions

COVID-19 impacted sleep quality and led to changes in blood oxygen saturation and breathing rate. The results of this study should be utilized for COVID-19-infected individuals’ physical rehabilitation following infection. Those who have not been infected with COVID-19 should be informed of self-protection measures to avoid contracting the disease. Although a statistically significant difference was identified, it was not clinically significant for detecting exercise-induced desaturation and changes in breathing rate. Thus, these results should be used with caution.

Supplemental Information