We thank Drs. Hung and Wei for their interest in our work on Coronavirus disease 2019 (COVID-19) and long-COVID.
Of course, we concur on the fact that several factors, including vaccination, virus strains, lifestyle, and body mass index, can influence the risk of developing long-COVID [1], [2]; however, these points are not pertinent to our study, since, as we previously clarified [3], we did not investigate the risk of long-COVID: in fact, all patients who completed the LINCOLN (L-Arginine and Vitamin C improve Long-COVID) survey had long-COVID when the questionnaire was administered [4]. Moreover, in Italy, where the study was conducted, > 90 % of the population has received at least two doses of COVID-19 vaccine.
The treatments, namely L-Arginine + Vitamin C to improve endothelial function and to reduce oxidation, respectively [5], [6], vs alternative treatment, had been started in all patients at least 28 days after the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) negativization. Nevertheless, performing the analysis in patients who specifically experienced the onset of long-COVID symptoms 28 days after the negativization ( Table 1), our findings are confirmed ( Table 2). It is also worth noting that the physicians who administered the questionnaire – please see appendix in [4] – considered only persistent symptoms. When examining the effort perception (modified Borg scale), we also observed a significantly lower value in the arm treated with L-Arginine + Vitamin C compared to the alternative treatment (1.1 ± 0.8 vs 5.2 ± 1.5, p < 0.0001), indicating a better tolerance.
Table 1.
Main characteristics of the two populations of patients who experienced the onset of long-COVID symptoms 28 days after the SARS-CoV-2 negativization. Data are mean±SD or percentages.
| Alternative treatment (n = 266) | L-Arginine + Vitamin C (n = 460) | p | |
|---|---|---|---|
| Age (y) | 57.0 ± 16.4 | 55.0 ± 16.0 | 0.102 |
| Male sex (%) | 49.6 | 47.0 | 0.488 |
| Hospitalization for COVID-19 (%) | 10.2 | 10.4 | 0.903 |
Table 2.
Survey results in the two groups of patients who experienced the onset of long-COVID symptoms 28 days after the SARS-CoV-2 negativization.
| Alternative treatment | L-Arginine + Vitamin C | p | ||
|---|---|---|---|---|
| Asthenia | Absent (%) | 0.8 | 94.3 | <0.0001 |
| Mild (%) | 7.1 | 5.2 | ||
| Severe (%) | 92.1 | 0.4 | ||
| Dyspnea | Absent (%) | 7.5 | 71.5 | <0.0001 |
| Mild (%) | 53.0 | 28.5 | ||
| Severe (%) | 39.5 | 0.0 | ||
| Chest tightness | Absent (%) | 29.7 | 85.9 | <0.0001 |
| Mild (%) | 45.5 | 13.9 | ||
| Severe (%) | 24.8 | 0.2 | ||
| Dizziness | Absent (%) | 66.5 | 87.4 | <0.0001 |
| Mild (%) | 26.6 | 11.3 | ||
| Severe (%) | 7.1 | 1.3 | ||
| Gastrointestinal disorders | Absent (%) | 64.7 | 87.6 | <0.0001 |
| Mild (%) | 24.1 | 12.0 | ||
| Severe (%) | 11.3 | 0.4 | ||
| Headache | Absent (%) | 38.7 | 82.2 | <0.0001 |
| Mild (%) | 43.2 | 16.3 | ||
| Severe (%) | 18.0 | 1.5 | ||
| Anosmia | Absent (%) | 56.4 | 87.2 | <0.0001 |
| Mild (%) | 30.8 | 11.5 | ||
| Severe (%) | 12.8 | 1.3 | ||
| Concentration difficulty | Absent (%) | 33.5 | 82.0 | <0.0001 |
| Mild (%) | 45.5 | 16.7 | ||
| Severe (%) | 21.1 | 1.3 | ||
| Sleeplessness | Absent (%) | 44.0 | 81.1 | <0.0001 |
| Mild (%) | 36.1 | 17.4 | ||
| Severe (%) | 19.9 | 1.5 |
Declaration of Competing Interest
None.
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