During the emergence of COVID-19, patients experience various symptoms, including fever, headaches, fatigue, and loss of smell and taste. In addition, many patient's factors and characteristics affect symptoms' severity, duration, and frequency[21][22].
The most prevalent symptoms in this study were fatigue, headache, loss of sense of smell, joint pain, loss of sense of taste, and cough, respectively. This finding aligns with other studies where cough, fever, and fatigue were one of the major early symptoms of infection[11–14]. On the other hand, some studies contradict the results concerning headaches[23, 24], while others support them[11]. This study showed that fever and cough declined with age, as revealed in other studies[25]. While adults aged between 31 and 40 reported the highest number of symptoms among all age groups, including loss of sense of smell and taste, cough, headache, and muscle pain[26].
Regarding the BMI-related emergence of symptoms, no significant differences were found among the categories. However, fatigue was the most common symptom among overweight and obese participants. This finding may be because obese individuals are at an increased risk of illness due to impaired immune systems[27]. In addition, overweight and obese patients are more likely to suffer from joint and muscle pain[28].
It has been suggested that the ABO blood group might be related to viral and bacterial infections and may affecting symptoms severity and frequency[29, 30]. In addition, blood group antigens are thought to affect pathogenesis by enabling the pathogen to take and modulate innate immune system responses[30, 31]. In this study, blood group A was associated with an increased risk of infection in most infected patients. A Chinese study supported the findings that blood group A was associated with a higher risk of infections. Furthermore, in that study, blood group O was associated with at the least risk for infection[32, 33]. In addition, blood group A participants experienced more loss of taste; a similar finding was reported in a Pakistani study[33].
Tobacco smoking is a known risk factor for a viral respiratory illness affecting the immune system’s response. Smoking causes damage to the airway epithelial cells impairing the integrity of the airway epithelium[34]. In Covid-19 patients, smokers are thought to have overexpression of ACE-2 receptors, which play a vital role in Sars COV-2 viral entry to the cells increasing the risk and severity of COVID-19 infection[35]. There are conflicting data about smoking and COVID-19 frequency and severity. In a Malaysian study, smoking was associated with a higher risk of complications with no significant disease outcomes[36]. In a recent systematic review, smokers were more likely to have severe symptoms of COVID-19 and be admitted to an Intensive Care Unit[37].
On the other hand, an ecological study in Europe revealed a negative association between smoking and COVID-19 prevalence and occurrence in 38 European countries[38]. In this study, nonsmokers were more vulnerable to infection than smokers. This finding was similar to other studies where smoking could be a protective factor against infection with covid-19[39, 40]. However, this finding cannot be extrapolated to the general population, and this study does not recommend smoking to prevent Sars Cov-2 infection or treatment.
Fatigue, fever, cough, headache, joint pain, and muscle pain were not significantly more common in nonsmokers based on the study results; this aligns with other studies that suggest no relation based on preexisting smoking status[41]. On the other hand, loss of sense of taste was significantly more prevalent in smokers. Although there are no suggested studies that significantly related loss of sense of taste to COVID-19 infection, some findings suggest that cigarette smoking is a major determinant in the reduced or altered taste function[42]. Based on findings in previous a study conducted, smoking was a major risk factor for the prevalence of ageusia [43].
Symptoms of loss of smell and taste have been reported by many patients infected with Sars Cov-2. It has also been proposed that patients with loss of smell have milder disease than patients who do not present with this symptom[44]. The study showed that older patients over 50 years of agehad less loss of the sense of smell compared to the rest of the age groups. This finding aligns with other studies, which show that older patients complain less about the loss of sense of smell during infection and that younger age groups suffer more often from anosmia[44]. The elderly may have less awareness of the loss of smell sensations, which may be underreported in this patient group [43].
Furthermore, the elderly are expected to have a decline in sensory function, including smell and taste. In addition, fatigue was also the most common symptom in the older age groups, while other studies reported that fever and cough were the highest in infected elderly patients[45]. This finding indicates that elderly patients with symptoms other than loss of smell or taste should get a thorough evaluation and assessment to avoid a missed diagnosis of possible Sars Cov-2 infection.
Regarding headache, it was significantly more prevalent in females compared to males as other findings also show that headache was more prevalent in young females[46]. On the other hand, in a COVID-19 pandemic survey study that included 3458 participants, the findings appeared to indicate that males had a higher headache prevalence rate than females, which may be related to cofactors such as comorbidities and overall health situation[46].
Participants with comorbid conditions are expected to have more symptoms and suffer from adverse events[47], including fatigue, which was not the case in this study. Results showed that obesity, hypertension, and diabetes patients were more likely to have COVID-19 symptoms. Patients with at least one comorbid condition suffered most from fatigue and headache. A meta-analysis conducted in 2019 revealed that hypertension, cardiovascular diseases, and diabetes were the leading existing chronic diseases in COVID-19 patients[48]. Furthermore, one study shows that diabetes, along with malignancy, was the leading comorbidity among covid-19 infected patients[49], and others show that hypertension was the most prevalent comorbidity[50, 51].