Characteristics of the study population, with and without a diagnosis of COVID-19
| Number (%) | P value | ||
| Individuals not diagnosed with COVID-19 (n=20 488) | Individuals diagnosed with COVID-19 (n=373) | ||
| Gender | |||
| Male | 6133 (29.9) | 121 (32.4) | 0.15 |
| Female | 14 306 (69.8) | 250 (67.0) | |
| Other | 36 (0.2) | 2 (0.5) | |
| Missing | 13 (0.1) | 0 (0) | |
| Age | |||
| 18–29 years | 1191 (5.8) | 51 (13.7) | <0.001 |
| 30–39 years | 1949 (9.5) | 39 (10.5) | |
| 40–49 years | 3644 (17.8) | 99 (26.5) | |
| 50–59 years | 5309 (25.9) | 99 (26.5) | |
| 60–69 years | 5359 (26.2) | 74 (19.8) | |
| 70 years or older | 3036 (14.8) | 11 (2.9) | |
| Highest educational level | |||
| Compulsory education | 2865 (14.0) | 30 (8.0) | 0.008 |
| Upper secondary, vocational or other education | 6303 (30.8) | 117 (31.4) | |
| Bachelor’s degree or diploma certificate | 6517 (31.8) | 135 (36.2) | |
| Master’s or PhD degree | 4685 (22.9) | 91 (24.4) | |
| Missing | 118 (0.6) | 0 (0) | |
| Average monthly income* | |||
| Low income | 3527 (17.2) | 50 (13.4) | <0.001 |
| Low-medium income | 5642 (27.5) | 88 (23.6) | |
| Medium income | 4993 (24.4) | 82 (22.0) | |
| Medium-high income | 3527 (17.2) | 91 (24.4) | |
| High income | 1825 (8.9) | 47 (12.6) | |
| Missing | 974 (4.8) | 15 (4.0) | |
| Residence | |||
| Capital area | 13 986 (68.3) | 270 (72.4) | 0.18 |
| Elsewhere in Iceland | 6352 (31.0) | 102 (27.3) | |
| Abroad | 140 (0.7) | 1 (0.3) | |
| Missing | 10 (0.0) | 0 (0) | |
| Marital status | |||
| In a relationship | 15 735 (76.8) | 302 (81.0) | 0.09 |
| Single | 4671 (22.8) | 71 (19.0) | |
| Missing | 82 (0.4) | 0 (0) | |
| BMI category (kg/m²) | |||
| <25, normal weight | 5931 (28.9) | 112 (30.0) | 0.70 |
| 25–30, overweight | 7931 (38.7) | 138 (37.0) | |
| >30, obese | 6127 (29.9) | 118 (31.6) | |
| Missing | 499 (2.4) | 5 (1.3) | |
| Smoking status | |||
| No | 17 873 (87.2) | 345 (92.5) | 0.002 |
| Yes | 2521 (12.3) | 26 (7.0) | |
| Missing | 94 (0.5) | 2 (0.5) | |
| Binge drinking | |||
| No | 18 255 (89.1) | 312 (83.6) | 0.02 |
| Yes | 2233 (10.9) | 61 (16.4) | |
| Previous diagnosis of psychiatric disorder | |||
| No | 14 510 (70.8) | 285 (76.4) | 0.02 |
| Yes | 5776 (28.2) | 84 (22.5) | |
| Missing | 202 (1.0) | 4 (1.1) | |
| Physical diseases | |||
| No comorbidities | 11 958 (58.4) | 263 (70.5) | <0.001 |
| One comorbidity | 5964 (29.1) | 86 (23.1) | |
| Two or more comorbidities | 2453 (12.0) | 21 (5.6) | |
| Missing | 113 (0.6) | 3 (0.8) | |
| Questionnaire answer date | |||
| 24–30 April | 7841 (38.3) | 102 (27.3) | <0.001 |
| 1–7 May | 5413 (26.4) | 76 (20.4) | |
| 8–23 May | 4999 (24.4) | 53 (14.2) | |
| 24 May–22 July | 2235 (10.9) | 142 (38.1) | |
| Time since diagnosis | |||
| Less than 2 weeks | – | 8 (2.1) | – |
| 2–4 weeks | – | 60 (16.1) | |
| More than 4 weeks | – | 305 (81.8) | |
*Income categories were defined as: low income, <1653 GBP; low-medium income, 1653–2755 GBP; medium income, 2756–3858 GBP; medium-high income, 3859–5511 GBP; high income, >5511 GBP (conversion rates according to Central Bank of Iceland, 24 April 2020).