The COVID-19 mainly affects the respiratory system, and some patients required intensive care due to a rapid progression of hypoxia, pneumonia, and acute respiratory distress syndrome. This study investigated the prevalence of symptomatic, comorbidities, and severity, and the associated factors of severity in COVID-19 patients. In this study, the sex distribution was not too different and it was in line with the studies done in China [19, 29]. The recent study reported that (14.8%) of patients were the older age and it seemed to be consistent with the finding obtained in the China study (12.3%) [19] and lower than the studies conducted in the USA (28.3%) [30] and Germany (26.7%) [31]. More than one-fourth of the patients (26.2%) were overweight or obese in this study and this result was lower than the findings of studies done in Thailand (32.9%) [32], Germany (38.2%) [31], and China (47.5%) [33]. The reason for these variations might be due to the difference in the socio-economic and geographical nature of the study area, variation in sample size, and distinction in lifestyle factors.
The prevalence of initial presenting symptoms (76.7%) in the current study was lower than studies done in Thailand (94.8%) [32] and Korea (91.3%) [34], but higher than in the China study (70.6%) [19]. This inconsistency might be due to variation of diagnostic and hospitalization criteria of COVID-19 patients. One explanation for the detection of nearly one-fourth of the asymptomatic patients in this study might be due to well achievement in case finding, contact tracing, and surveillance of COVID-19 cases by the healthcare providers. A substantial number of undocumented infections leading to no symptoms might enable the rapid spread of SARS-CoV-2 [35]. In Myanmar, the government expanded the testing capacity for primary contacts and imported cases as a priority of testing. All COVID-19 patients including symptomatic and asymptomatic who were confirmed by RT-PCR and Standard Q COVID-19 Antigen Rapid Diagnosis Test were hospitalized in designated hospitals. In the current study, it was surprising that loss of smell, apart from fever and cough, was one of the most common symptoms, and this finding was contrary to that of previous studies done in the same constitution reported that fatigue, sore throat, shortness of breath and rhinorrhea were the most common presenting symptoms [30, 32–34, 36].
The prevalence of comorbid diseases (35.8%) in COVID-19 patients was higher than the findings of the studies conducted in China (15.8%) [19] and Thailand (25.0%) [32]. This discrepancy could be attributed to variation in the prevalence of chronic diseases across age, gender distribution, and geographic region. Non-communicable diseases (NCDs) were identified as a priority public health problem in Myanmar and cardiovascular disease was one of the NCDs with the highest impact on mortality [37]. Over 2012 to 2017, most of the admitted patients with NCDs were middle and older aged population with the median and interquartile range of 39 (25–55) years and (51.6%) of those were males [38]. In the current study, the most common comorbidities were hypertension and diabetes mellitus and these results supported the findings of the earlier studies conducted in hospitalized COVID-19 patients [19, 30, 31, 34, 36].
As the severity of COVID-19, the prevalence of pneumonia in this study was (23.3%) and it was agreed with the finding of other study revealed that (23.6%) of the COVID-19 patients developed pneumonia [31]. However, it was lower than the results of the studies conducted in Thailand (38.9%) [32], Korea (73.2%) [34], and China (67.9%) [19] and (83.5%) [29], respectively. It was possible that these results were due to variability of chest imaging findings (chest radiograph or computerized tomography), the difference in criteria of patient isolation and hospitalization, and contrast to protocol and management guidelines of COVID-19 patients. The symptomatic patients tend to have severe inflammation in the lungs, which more commonly leads to disease progression. The symptomatic patients had a higher risk of developing bilateral pneumonia and less likely to show improvement of pneumonia than asymptomatic patients [19].
In the recent study, age was a significant determinant of pneumonia in COVID-19 patients and it might be explained by the fact that older people were particularly susceptible to develop more infections as natural immunity declined gradually at older ages. Another explanation for this finding could be that the older people might have more expression of ACE2 encoded by the ACE2 gene and have other conventional factors such as reduced immunity, poor organ function, or coexisting comorbid diseases which might have increased risk of disease severity [39]. This finding was keeping with the previous studies done in Thailand [32], China [29, 33, 36], and Korea [34] reported that older age was a potential predictive factor of pneumonia in SARS-CoV-2 infected patients.
The immune function and response in viral infections were influenced by lifestyle factors, overweight or obesity. This study confirmed that overweight or obesity was associated with the development of pneumonia in COVID-19 patients. The possible reason might be due to the fact that people with overweight or obesity might have comorbidities including metabolic diseases, cardiovascular diseases, and cancers that were susceptible to infection. Moreover, they had a significantly large amount of ACE2 receptor in adipose tissue and were more likely to SARS-CoV-2 infection, which resulted in increased viral shedding, immune inactivation, and cytokine storm [40]. This finding also supported the evidence from other studies conducted in Thailand [32], China [33], Korea [34], and Germany [31] reported that overweight or obesity patients were more likely to get pneumonia than normal weight patients.
Tobacco contains components that disrupt the normal epithelial lining of the respiratory system leading to increased oxidative injury and impairment of mucociliary clearance [41]. Smoking was also a significant predictor of pneumonia in COVID-19 patients in the current study. This could be because tobacco smoke suppressed the function of innate immune cells, including respiratory epithelium, alveolar surfactant, macrophage, neutrophils, and lymphocytes. This could make smokers were more susceptible to develop the complications of COVID-19, such as pneumonia. This result matched those observed in earlier studies done in China [42, 43] and Turkey [44] reported that there was an association between the current smoking status and disease severity of COVID-19. However, this finding was contrary to previous studies which had evidence that smoking was not associated with the severity of COVID-19 [34, 36, 45].
The COVID-19 patients with a history of alcohol drinking were more likely to develop pneumonia than those who were non-drinkers. A possible explanation for this might be alcohol-induced oxidative stress leading to depletion of the critical antioxidant glutathione and deterioration of alveolar barrier integrity and modulation of the immune response [46]. Alcohol also had a negative impact on lung innate defense and response to lung injury with an impairment of the ability to fight infection [47]. In addition, alcohol consumption lead to over expression of ACE2 receptors, which could support the facilitated proliferation of SARS-CoV-2 into the cells [48]. This finding was accorded with the results of other studies conducted in USA [47] and Denmark [49].
There were some limitations in this study. Firstly, it was relatively difficult to establish a causal relationship between severity and independent variables due to the cross-sectional nature of this study. A longitudinal study with a larger sample size could be applied to find out the higher strength of association. Secondly, although the results were representative of the population with the same demographic characteristics, further research using a random sampling method should be conducted to have a more representative cohort. Thirdly, the asymptomatic patients might have developed symptoms later and they could be over looked. Lastly, the patients with unrecognized or unknown comorbidity would not be detected and therefore, further studies should obtain more information about the existing unrecognized comorbid diseases in order to ascertain association.