Table 1.
Patient demographics and clinical characteristics on admission
| Age category |
Wave category |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Number of cases | Subcategories | Total | Under 18 (0–17 years) | Young (18–39 years) | Middle age (40–64 years) | Older (≥65 years) | Wave 1 | Wave 2 | Wave 3 | |
| Demographics | ||||||||||
| Male sex | 33,551 | 18,985 (56·6) | 608 (55·1) | 4030 (55·2) | 7424 (64·9) | 6917 (50·5) | 3139 (58·5) | 6784 (58) | 9062 (55) | |
| Female sex | 14,566 (43.4) | 496 (44.9) | 3277 (44.8) | 4020 (35.1) | 6770 (49.5) | 2233 (41.5) | 4908 (42) | 7428 (45) | ||
| Age (median) [IQR], years | 33,542 | 58 [39, 74] | 9 [3, 14] | 28 [23, 34] | 53 [47, 58] | 77 [71, 85] | 56 [40, 71] | 50 [30, 69] | 64 [47, 78] | |
| Wave | 33,554 | First | 5372 (16) | 109 (9·9) | 1175 (16·1) | 2138 (18·7) | 1949 (14·2) | |||
| Second | 11,692 (34·8) | 459 (41·6) | 3772 (51·6) | 3924 (34·3) | 3532 (25·8) | |||||
| Third | 16,490 (49·1) | 536 (48·6) | 2360 (32·3) | 5382 (47) | 8206 (60) | |||||
| Japanese ethnicity | 33,190 | 31,680 (95·5) | 955 (87·5) | 6561 (90·7) | 10,747 (95) | 13,407 (99) | 5125 (95·7) | 10,950 (94·1) | 15,605 (96·3) | |
| Former or current smoker | 33,460 | 11,721 (35) | 12 (1.1) | 2399 (32.9) | 4977 (43·6) | 4332 (31·7) | 1882 (35·2) | 4420 (38) | 5419 (32·9) | |
| Alcohol consumption a | 32,866 | Daily | 2297 (7) | 2 (0·2) | 589 (8·2) | 1130 (10·1) | 576 (4·3) | 347 (7·3) | 1049 (9) | 901 (5·5) |
| Occasional | 10,525 (32) | 7 (0·6) | 2941 (41·2) | 4553 (40·9) | 3021 (22·4) | 1436 (30·1) | 4157 (35·7) | 4932 (30) | ||
| BMI (median) [IQR], kg/m2 | 27,180 | 23·3 [20·7, 26·3] | 18·2 [16, 20·7] | 22·4 [20·1, 25·7] | 24·7 [22·1, 27·8] | 22·8 [20·3, 25·3] | 23·1 [20·5, 26] | 23·1 [20·5, 26·3] | 23·4 [20·8, 26·4] | |
| Immunosuppressionb | 32,840 | 708 (2·2) | 8 (0·7) | 57 (0·8) | 212 (1·9) | 431 (3·2) | 145 (2·8) | 199 (1·7) | 364 (2·3) | |
| Exposure within 14 days | ||||||||||
| Travel to COVID-19 epidemic countries | 33,329 | 564 (1·7) | 36 (3·3) | 189 (2·6) | 196 (1·7) | 143 (1·1) | 345 (6·4) | 132 (1·1) | 87 (0·5) | |
| Close contact with COVID-19 casesc | 33,358 | 18,269 (54·8) | 914 (83) | 3671 (50·5) | 5475 (48·2) | 8203 (60·3) | 3035 (56·5) | 6039 (51·8) | 9195 (56·3) | |
| Unknown | 3915 (11·7) | 40 (3·6) | 793 (10·9) | 1468 (12·9) | 1614 (11·9) | 654 (12·2) | 1212 (10·4) | 2049 (12·6) | ||
| Contact details | 33,554 | Family | 6968 (20·8) | 713 (64·6) | 948 (13) | 2178 (19) | 3128 (22·9) | 912 (17) | 2273 (19·4) | 3783 (22·9) |
| Workplace | 3354 (10) | 2 (0·2) | 1288 (17·6) | 1656 (14·5) | 407 (3) | 601 (11·2) | 1265 (10·8) | 1488 (9) | ||
| Healthcare facility | 4785 (14·3) | 2 (0·2) | 346 (4·7) | 675 (5·9) | 3760 (27·5) | 913 (17) | 1049 (9) | 2823 (17·1) | ||
| Educational facility | 253 (0·8) | 143 (13) | 75 (1) | 24 (0·2) | 10 (0·1) | 15 (0·3) | 108 (0·9) | 130 (0·8) | ||
| Meals with more than 3 persons (excl. family members) | 32,783 | 4643 (14·2) | 95 (8·7) | 1605 (22·5) | 1595 (14·4) | 1346 (10) | 539 (11·2) | 2030 (17·4) | 2074 (12·7) | |
| Unknown | 9554 (29·1) | 204 (18·7) | 2050 (28·7) | 3537 (31·9) | 3763 (28) | 1951 (40·4) | 3218 (27·6) | 4385 (26·9) | ||
| Stay in a closed and crowded spaced | 32,761 | 4533 (13·8) | 74 (6·8) | 1645 (23·1) | 1561 (14·1) | 1250 (9·3) | 658 (13·6) | 2177 (18·7) | 1698 (10·4) | |
| Unknown | 8745 (26·7) | 181 (16·6) | 1960 (27·5) | 3389 (30·6) | 3215 (23·9) | 1683 (34·9) | 2875 (24·7) | 4187 (25·7) | ||
| Occupation | ||||||||||
| Healthcare worker | 32,811 | 1753 (5·3) | 3 (0·3) | 667 (9·3) | 894 (8) | 188 (1·4) | 455 (9·4) | 507 (4·3) | 791 (4·9) | |
| Restaurant worker | 32,753 | 1128 (3·4) | 1 (0·1) | 423 (5·9) | 427 (3·8) | 277 (2·1) | 164 (3·4) | 555 (4·8) | 409 (2·5) | |
| Specific service workere | 32,744 | 775 (2·4) | 2 (0·2) | 503 (7·1) | 200 (1·8) | 70 (0·5) | 126 (2·6) | 446 (3·8) | 203 (1·2) | |
| Conditions at admissionf | ||||||||||
| Days from symptom onset to hospitalisation (Median) [IQR] | 30,244 | 5 [2, 7] | 3 [1, 5] | 4 [2, 7] | 5 [3, 8] | 4 [2, 7] | 7 [4, 10] | 4 [2, 7] | 4 [2, 7] | |
| Severe condition at admission | 33,554 | 9587 (28·6) | 214 (19·4) | 567 (7·8) | 2906 (25·4) | 5898 (43·1) | 1767 (32·9) | 2544 (21·8) | 5276 (32) | |
| O2 administration method | 33,287 | Room air | 28,537 (85·7) | 1045 (99·4) | 7115 (98·1) | 10,031 (88·2) | 10,335 (76) | 4417 (82·7) | 10,451 (90·1) | 13,669 (83·6) |
| O2 administration | 4312 (13) | 6 (0·6) | 129 (1·8) | 1174 (10·3) | 3002 (22·1) | 779 (14·6) | 1025 (8·8) | 2508 (15·3) | ||
| BiPAP/CPAP, IMV, ECMO | 438 (1·3) | 0 (0) | 7 (0·1) | 173 (1·5) | 258 (1·9) | 143 (2·7) | 121 (1) | 174 (1·1) | ||
| O2 administered through | 4306 | Cannula | 2941 (68·3) | 4 (66·7) | 102 (79·1) | 836 (71·4) | 1998 (66·6) | 490 (63) | 734 (71·8) | 1717 (68·5) |
| Mask | 812 (18·9) | 2 (33·3) | 22 (17·1) | 201 (17·2) | 587 (19·6) | 152 (19·5) | 167 (16·3) | 493 (19·7) | ||
| Reservoir mask | 484 (11·2) | 0 (0) | 5 (3·9) | 117 (10) | 362 (12·1) | 126 (16·2) | 106 (10·4) | 252 (10·1) | ||
| High-flow therapy | 69 (1·6) | 0 (0) | 0 (0) | 17 (1·5) | 52 (1·7) | 10 (1·3) | 15 (1·5) | 44 (1·8) | ||
| Signs and symptoms on admissiong | ||||||||||
| Asymptomatic on admission | 33,084 | 3029 (9·2) | 320 (29·2) | 582 (8·1) | 621 (5·5) | 1505 (11·1) | 321 (6·5) | 1183 (10·1) | 1525 (9·3) | |
| Fever (≥37·5°C) | 33,536 | 16,208 (48·3) | 319 (28·9) | 2911 (39·9) | 6222 (54·4) | 6751 (49·4) | 2807 (52·3) | 5198 (44·5) | 8203 (49·8) | |
| Cough | 33,536 | 16,295 (48·6) | 306 (27·7) | 3464 (47·4) | 6493 (56·8) | 6025 (44) | 2816 (52·5) | 5228 (44·7) | 8251 (50·1) | |
| Bloody sputum | 16,252 | 242 (1·5) | 2 (0·7) | 41 (1·2) | 95 (1·5) | 103 (1·7) | 43 (1·5) | 69 (1·3) | 130 (1·6) | |
| Sore throat | 33,539 | 5415 (16·1) | 133 (12·1) | 1763 (24·1) | 2247 (19·6) | 1270 (9·3) | 722 (13·4) | 2050 (17·5) | 2643 (16) | |
| Rhinorrhoea | 33,539 | 3084 (9·2) | 246 (22·3) | 1060 (14·5) | 1090 (9·5) | 687 (5) | 441 (8·2) | 898 (7·7) | 1745 (10·6) | |
| Dyspnoea | 33,542 | 6941 (20·7) | 18 (1·6) | 988 (13·5) | 2857 (25) | 3078 (22·5) | 1350 (25·1) | 2005 (17·2) | 3586 (21·8) | |
| Chest pain | 33,541 | 932 (2·8) | 4 (0·4) | 240 (3·3) | 448 (3·9) | 240 (1·8) | 182 (3·4) | 332 (2·8) | 418 (2·5) | |
| Myalgia | 33,542 | 2876 (8·6) | 21 (1·9) | 777 (10·6) | 1426 (12·5) | 651 (4·8) | 372 (6·9) | 1005 (8·6) | 1499 (9·1) | |
| Headache | 33,535 | 5119 (15·3) | 115 (10·4) | 1721 (23·6) | 2429 (21·2) | 852 (6·2) | 717 (13·4) | 1994 (17·1) | 2408 (14·6) | |
| Fatigue | 33,535 | 11,700 (34·9) | 101 (9·1) | 2472 (33·8) | 4795 (41·9) | 4328 (31·6) | 2076 (38·7) | 3948 (33·8) | 5676 (34·4) | |
| Abdominal pain | 33,528 | 608 (1·8) | 21 (1·9) | 176 (2·4) | 227 (2) | 184 (1·3) | 124 (2·3) | 216 (1·8) | 268 (1·6) | |
| Vomit | 33,528 | 1230 (3·7) | 25 (2·3) | 302 (4·1) | 452 (4) | 451 (3·3) | 207 (3·9) | 444 (3·8) | 579 (3·5) | |
| Diarrhoea | 33,530 | 3156 (9·4) | 69 (6·3) | 818 (11·2) | 1393 (12·2) | 875 (6·4) | 604 (11·3) | 1232 (10·5) | 1320 (8) | |
| Dysgeusia | 33,535 | 5415 (16·1) | 101 (9·1) | 2238 (30·6) | 2145 (18·8) | 929 (6·8) | 894 (16·6) | 2397 (20·5) | 2124 (12·9) | |
| Olfactory abnormality | 33,532 | 4878 (14·5) | 87 (7·9) | 2219 (30·4) | 1881 (16·4) | 689 (5) | 734 (13·7) | 2239 (19·2) | 1905 (11·6) | |
| Rash | 32,897 | 224 (0·7) | 6 (0·5) | 58 (0·8) | 101 (0·9) | 59 (0·4) | 38 (0·8) | 93 (0·8) | 93 (0·6) | |
Data are presented as n (%) unless otherwise indicated.
As the number of missing values differed for each parameter, the number of cases in each parameter's age/wave category was used as the denominator for calculating the percentage.
Abbreviations: BiPAP/CPAP, bilevel positive airway pressure/continuous positive airway pressure; BMI, body mass index; IMV, invasive mechanical ventilation; ECMO, extracorporeal membrane oxygenation; IQR, interquartile range.
Daily, ≥3 cans of beer per day; occasional includes daily alcohol intake of <3 cans beer per day.
Immunosuppression includes neutropenia (<500 neutrophils/μL); glucocorticoid/steroid use within 1 month (doses greater or equal to an equivalent of 20 mg of prednisone per day for at least 1 month); chemotherapy, radiation therapy, or immunosuppressant use (such as antitumor necrosis factor α therapy, anti-IL-6 receptor/anti-CD20 monoclonal antibodies, selective T-cell co-stimulation blocker, methotrexate, tacrolimus) in the past 3 months; and/or post-transplantation, asplenia, or primary immunodeficiency syndrome. Multiple immunosuppressants were used in some cases.
“Close contact” was defined as in the International Severe Acute Respiratory and Emerging Infection Consortium case record form.9
Close contact in closed and crowded spaces, include sports gyms, live music clubs, karaokes, game centers, buffets, indoor parties, conferences, or nightclubs/bars.
Included nightlife business workers at bars and pubs, host and hostess clubs, nightclubs, and other similar businesses.28
First available data at presentation/admission within 24 hours.
Signs and symptoms observed/reported at admission and associated with the presented episode of acute illness.