TABLE 1.
Socio‐demographic, clinical and study characteristics of participants enrolled between May 2020 and June 2021 who completed at least one symptom survey in the RECoVERED cohort in Amsterdam, the Netherlands.
| Initial COVID‐19 severity a | p‐Value | ||||
|---|---|---|---|---|---|
| Total | Mild | Moderate | Severe/critical | ||
| N = 292 | N = 86 | N = 127 | N = 79 | ||
| Baseline socio‐demographic and medical characteristics | |||||
| Sex | 0.25 | ||||
| Male | 170 (58%) | 44 (51%) | 76 (60%) | 50 (63%) | |
| Female | 122 (42%) | 42 (49%) | 51 (40%) | 29 (37%) | |
| Age, years | 51.0 (36.0–62.0) | 41.0 (29.0–54.0) | 50.0 (34.0–62.0) | 60.0 (51.0–66.0) | <0.001 |
| BMI, kg/m2 | 26.1 (23.5–29.4) | 24.5 (22.8–27.7) | 26.2 (23.5–29.4) | 27.4 (25.5–33.3) | <0.001 |
| BMI category | <0.001 | ||||
| Normal weight | 121 (41%) | 50 (58%) | 52 (41%) | 19 (24%) | |
| Overweight | 101 (35%) | 23 (27%) | 45 (35%) | 33 (42%) | |
| Obese | 68 (23%) | 13 (15%) | 30 (24%) | 25 (32%) | |
| Missing | 2 (1%) | 0 (0%) | 0 (0%) | 2 (3%) | |
| Migration background | 0.003 | ||||
| Dutch | 183 (63%) | 62 (72%) | 77 (61%) | 44 (56%) | |
| Non‐Dutch, OECD high‐income | 31 (11%) | 11 (13%) | 16 (13%) | 4 (5%) | |
| Non‐Dutch, OECD low/middle income | 71 (24%) | 10 (12%) | 32 (25%) | 29 (37%) | |
| Missing | 7 (2%) | 3 (3%) | 2 (2%) | 2 (3%) | |
| Smoking | 0.13 | ||||
| Non‐smoker | 182 (62%) | 52 (60%) | 74 (58%) | 56 (71%) | |
| Smoker | 19 (7%) | 8 (9%) | 10 (8%) | 1 (1%) | |
| Ex‐smoker | 88 (30%) | 24 (28%) | 43 (34%) | 21 (27%) | |
| Missing | 3 (1%) | 2 (2%) | 0 (0%) | 1 (1%) | |
| Highest level of education | <0.001 | ||||
| None, primary or secondary education | 41 (14%) | 7 (8%) | 22 (17%) | 12 (15%) | |
| Vocational training | 70 (24%) | 9 (10%) | 32 (25%) | 29 (37%) | |
| University education | 173 (59%) | 67 (78%) | 71 (56%) | 35 (44%) | |
| Missing | 8 (3%) | 3 (3%) | 2 (2%) | 3 (4%) | |
| Number of COVID‐19 high‐risk comorbidities b | <0.001 | ||||
| 0 | 160 (55%) | 61 (71%) | 75 (59%) | 24 (30%) | |
| 1 | 72 (25%) | 18 (21%) | 28 (22%) | 26 (33%) | |
| 2 | 36 (12%) | 5 (6%) | 16 (13%) | 15 (19%) | |
| 3 or more | 24 (8%) | 2 (2%) | 8 (6%) | 14 (18%) | |
| COVID‐19‐related clinical characteristics | |||||
| Symptom status at baseline | 0.45 | ||||
| Symptomatic | 287 (98%) | 85 (99%) | 127 (100%) | 75 (95%) | |
| Asymptomatic | 2 (1%) | 1 (1%) | 0 (0%) | 1 (1%) | |
| Missing | 3 (1%) | 0 (0%) | 0 (0%) | 3 (4%) | |
| Hospital admission | 141 (48%) | 4 (5%) | 60 (47%) | 77 (97%) | <0.001 |
| ICU admission | 40 (14%) | 0 (0%) | 0 (0%) | 40 (51%) | <0.001 |
| Days from illness onset to COVID‐19 diagnosis | 4 (2–10) | 3 (1–8) | 4 (2–11) | 7 (2–11) | 0.13 |
| Days from illness onset to hospitalisation | 9 (7–14) | 43 (9–85) | 10 (8–16) | 9 (7–12) | 0.10 |
| Days from illness onset to ICU admission | 10 (7–12) | NA | NA | 10 (7–12) | |
| Received oxygen therapy before or during follow‐up | 135 (46%) | 0 (0%) | 59 (46%) | 76 (96%) | <0.001 |
| Received steroid treatment | <0.001 | ||||
| No steroid | 211 (72%) | 86 (100%) | 88 (69%) | 37 (47%) | |
| Dexamethasone | 55 (19%) | 0 (0%) | 27 (21%) | 28 (35%) | |
| Other steroid | 26 (9%) | 0 (0%) | 12 (9%) | 14 (18%) | |
| Maximal HR, beats/min c | 82 (72–94) | 75 (67–81) | 84 (76–94) | 94 (79–107) | <0.001 |
| Maximal RR, breaths/min c | 20 (16–24) | 16 (16–16) | 20 (20–24) | 24 (20–32) | <0.001 |
| Lowest SpO2, % c | 96 (91–98) | 98 (97–99) | 96 (93–98) | 88 (80–90) | <0.001 |
| Received COVID‐19 primary vaccination series | NA | ||||
| Not vaccinated | 24 (8%) | 2 (2%) | 13 (10%) | 9 (11%) | |
| Vaccinated | 232 (79%) | 72 (84%) | 102 (80%) | 58 (73%) | |
| LTFU before vaccination | 36 (12%) | 12 (14%) | 12 (9%) | 12 (15%) | |
| Time from illness onset to first vaccination, days | 244 (139–360) | 203 (130–310) | 241 (162–318) | 372 (131–393) | NA |
| Died during follow‐up | 1 (0%) | 0 (0%) | 1 (1%) | 0 (0%) | NA |
| Number of reinfections | NA | ||||
| 0 | 222 (76%) | 57 (66%) | 92 (72%) | 73 (92%) | |
| 1 | 65 (22%) | 27 (31%) | 33 (26%) | 5 (6%) | |
| 2 or more | 5 (1%) | 2 (2%) | 2 (2%) | 1 (1%) | |
| Long COVID status at 12 weeks after illness onset | <0.001 | ||||
| No (recovered within 12 weeks) | 115 (39%) | 54 (63%) | 43 (34%) | 18 (23%) | |
| Yes (did not recover within 12 weeks) | 177 (61%) | 32 (37%) | 84 (66%) | 61 (77%) | |
| Study characteristics | |||||
| Place of recruitment | <0.001 | ||||
| Non‐hospital | 143 (49%) | 75 (87%) | 65 (51%) | 3 (4%) | |
| Hospital | 149 (51%) | 11 (13%) | 62 (49%) | 76 (96%) | |
| Type of inclusion | <0.001 | ||||
| Prospective | 209 (72%) | 73 (85%) | 99 (78%) | 37 (47%) | |
| Retrospective | 83 (28%) | 13 (15%) | 28 (22%) | 42 (53%) | |
| Days from illness onset to inclusion in study | 12 (6–51) | 7 (4–12) | 12 (6–32) | 42 (14–89) | <0.001 |
| Lost to follow‐up | 109 | 26 | 40 | 43 | NA |
Note: Continuous variables presented as median (IQR) and compared using the Kruskal–Wallis test; categorical and binary variables presented as n (%) and compared using the Pearson χ 2 test (or Fisher exact test if n < 5). Time‐dependent outcomes not compared between groups due to bias resulting from differing follow‐up lengths.
Abbreviations: BMI, body mass index; COVID‐19, coronavirus disease 2019; HR, heart rate; ICU, intensive care unit; LTFU, lost to follow‐up; NA, not applicable; OECD, Organisation for Economic Co‐operation and Development; RR, respiratory rate; SpO2, oxygen saturation on room air.
Clinical severity groups defined as: mild as having an RR < 20/min and SpO2 on room air >94% at both D0 and D7; moderate disease as having a RR 20–30/min, SpO2 90%–94% and/or receiving oxygen therapy at D0 or D7; severe disease as having a RR > 30/min or SpO2 < 90% at D0 or D7; critical disease as requiring ICU admission.
COVID‐related comorbidities are based on WHO Clinical Management Guidelines and include: cardiovascular disease (including hypertension), chronic pulmonary disease (excluding asthma), renal disease, liver disease, cancer, immunosuppression (excluding HIV, including previous organ transplantation), previous psychiatric illness and dementia.
Physical measurements at D0 and D7 study visits. Oxygen saturation measured on room air if possible or retrieved from ambulance records for hospitalised participants admitted on oxygen on day of enrollment.