Table 1. Results of meta-regression to explore the source of heterogeneity.
| No of studies | Heterogeneity (I2) | Amount of heterogeneity accounted for (R2) (%) | |||
|---|---|---|---|---|---|
| Follow-up period | Age | Gender (male) | |||
| Pain-related symptoms | |||||
| Chest pain | 17 | 99 | 0 | 0 | 0 |
| Headache | 21 | 99 | 0 | 0 | 0 |
| Arthralgia | 13 | 99 | 0 | 0 | 0 |
| Neuralgia | 3 | 97 | 100 (+) | 92 (-) | 69 (+) |
| Abdominal pain | 10 | 98 | 0 | 0 | 0 |
| Myalgia | 18 | 100 | 0 | 0 | 0 |
| Sore throat | 17 | 99 | 0 | 0 | 0 |
| Ear pain | 4 | 99 | 0 | 0 | 0 |
| Other symptoms | |||||
| Fatigue | 28 | 99 | 0 | 0 | 0 |
| Insomnia | 7 | 100 | 44 (+) | 28 (-) | 75 (+) |
| Dyspnea | 23 | 99 | 34 (+) | 0 | 0 |
| Weakness | 5 | 98 | 0 | 64 (-) | 0 |
| Anosmia | 24 | 99 | 0 | 35 (-) | 0 |
| Cough | 23 | 99 | 0 | 42 (-) | 10 (-) |
| Ageusia | 19 | 99 | 0 | 0 | 19 (-) |
| Memory impairment | 9 | 98 | 73 (+) | 5 (+) | 40 (+) |
| Confusion | 5 | 94 | 0 | 0 | 0 |
| Depression | 10 | 99 | 55 (-) | 0 | 23 (+) |
| Fever | 17 | 99 | 0 | 0 | 0 |
| Rhinorrhea | 8 | 98 | 0 | 0 | 0 |
| Anxiety | 8 | 99 | 66 (+) | 0 | 67 (+) |
| Palpitation | 8 | 100 | 0 | 0 | 0 |
| Sneezing | 3 | 99 | 0 | 0 | 0 |
| Alopecia | 6 | 96 | 0 | 0 | 0 |
| Anorexia | 9 | 99 | 0 | 0 | 0 |
| Nasal blockage | 4 | 74 | 33 (-) | 0 | 70 (+) |
| Diarrhea | 19 | 99 | 0 | 0 | 0 |
| Vertigo (Dizziness) | 13 | 99 | 0 | 0 | 0 |
| Weight loss | 13 | 93 | 23 (-) | 0 | 40 (+) |
| Sputum | 6 | 50 | 65 (-) | 0 | 0 |
| Chills | 6 | 99 | 72 (+) | 0 | 77 (+) |
| Nausea | 11 | 99 | 54 (+) | 1 (-) | 0 |
| Vomiting | 6 | 91 | 7 (+) | 0 | 0 |
R2 represents a measure of the amount of heterogeneity that can be explained by the covariate. Bold numbers indicate that a significant correlation was found between the symptom and the covariate. + or–in parenthesis indicates a positive or negative coefficient in the regression model. Note that for insomnia and follow-up period, for instance, the incidence of insomnia is significantly higher when the follow-up period increases (positive correlation). Note that for ageusia and sex, the incidence of ageusia is significantly higher when the ratio of males in a study population decreases (inverse correlation).