Fig 1.
Proportions of patients with ME/CFS related to long COVID who were infected during the three variant periods.
The percentages of ME/CFS patients and non-ME/CFS patients (ME/CFS: n = 62; non-ME/CFS: n = 677) are shown by the period in which they were infected. The χ2 test was performed for the proportions of ME/CFS patients between the variant phases, and *p<0.05 and ***p<0.001 were considered statistically significant.
Table 1.
Numbers and proportions of long COVID patients who met the ME/CFS criteria.
Table 2.
Numbers and proportions of long COVID patients who met the ME/CFS criteria in each period.
Table 3.
Backgrounds of patients with ME/CFS related to long COVID and non-ME/CFS patients.
Table 4.
Physical and mental parameters for characterization of patients with ME/CFS related to long COVID and non-ME/CFS patients.
Fig 2.
Comparison of the clinical characteristics of long COVID patients in the ME/CFS group and the non-ME/CFS group in the three variant periods.
The percentages of patients with long COVID symptoms in the ME/CFS group (Total: n = 62; Preceding period: n = 27; Delta-dominant period: n = 19; Omicron-dominant period: n = 16) and non-ME/CFS group (Total: n = 677; Preceding period: n = 86; Delta-dominant period: n = 120; Omicron-dominant period: n = 471) are shown. The χ2 test was performed for each symptom between the two groups, and *p<0.05, **p<0.01, and ***p<0.001 were considered statistically significant.
Fig 3.
Serum ferritin levels in long COVID patients in the ME/CFS group and non-ME/CFS group.
Serum ferritin levels are presented by sex (A: Male: n = 300; B: Female: n = 356) and separated by the onset periods of COVID-19 (Preceding period: n = 110; Delta-dominant period: n = 129; Omicron-dominant period: n = 417). The Mann-Whitney U test was performed to compare the levels between the two groups, and *p< 0.05 was considered statistically significant.
Fig 4.
Prevalence of brain fog symptoms in long COVID patients in the ME/CFS group and non-ME/CFS group.
Percentages of patients who had brain fog symptoms are shown on the basis of the onset periods of COVID-19 (Total: n = 739; Preceding period: n = 113; Delta-dominant period: n = 139; Omicron-dominant period: n = 487). The χ2 test was performed for the proportions of patients with brain fog between the two groups in each variant phase, and **p<0.01 and ***p<0.001 were considered statistically significant.
Fig 5.
Vaccination rates in the ME/CFS group and non-ME/CFS group.
Percentages of vaccinated patients are shown on the basis of the onset periods of COVID-19 (Total: n = 729; Preceding period: n = 112; Delta-dominant period: n = 135; Omicron-dominant period: n = 482). The χ2 test was performed for the proportions of vaccinated patients between the two groups in each variant phase.