TABLE 1.
Characteristics of the included participants from the UK Biobank.
| Covariate | Total (N = 435,040) | Asthma (N = 58,635) | No asthma (N = 376,405) | P |
| Age at baseline (years), Mean (SD) | 56.50 (8.11) | 56.13 (8.27) | 56.56 (8.09) | < 0.001 |
| Age category (years), N (%) | < 0.001 | |||
| <50 | 102,949 (23.7) | 15,105 (25.8) | 87,844 (23.3) | |
| 50–59 | 144,179 (33.1) | 19,133 (32.6) | 125,046 (33.2) | |
| > 60 | 187,912 (43.2) | 24,397 (41.6) | 163,515 (43.5) | |
| Sex, N (%) | < 0.001 | |||
| Female | 233,393 (53.6) | 33,371 (56.9) | 200,022 (53.1) | |
| Male | 201,647 (46.4) | 25,264 (43.1) | 176,383 (46.9) | |
| Ethnicity, N (%) | < 0.001 | |||
| White | 395,084 (90.8) | 53,376 (91.0) | 341,708 (90.8) | |
| Mixed | 15,895 (3.7) | 2,150 (3.7) | 13,745 (3.7) | |
| Asian or Asian British | 15,163 (3.5) | 1,917 (3.3) | 13,246 (3.5) | |
| Black or Black British | 2,348 (0.5) | 357 (0.6) | 1,991 (0.5) | |
| Chinese | 1,364 (0.3) | 134 (0.2) | 1,230 (0.3) | |
| Other ethnic groups | 3,726 (0.9) | 493 (0.8) | 3,233 (0.9) | |
| Unknown | 1,460 (0.3) | 208 (0.4) | 1,252 (0.3) | |
| Average total household income before tax (€), N (%) | < 0.001 | |||
| Less than 18,000 | 83,214 (19.1) | 12,644 (21.6) | 70,570 (18.7) | |
| 18,000–30,999 | 94,586 (21.7) | 12,277 (20.9) | 82,309 (21.9) | |
| 31,000–51,999 | 97,873 (22.5) | 12,544 (21.4) | 85,329 (22.7) | |
| 52,000–100,000 | 77,067 (17.7) | 9,992 (17.0) | 67,075 (17.8) | |
| Greater than 100,000 | 20,583 (4.7) | 2,662 (4.5) | 17,921 (4.8) | |
| Unknown | 61,717 (14.2) | 8,516 (14.5) | 53,201 (14.1) | |
| Education, N (%) | < 0.001 | |||
| College or university degree | 142,036 (32.6) | 19,049 (32.5) | 122,987 (32.7) | |
| Professional qualifications | 51,300 (11.8) | 6,881 (11.7) | 44,419 (11.8) | |
| A Levels/AS Levels or equivalent | 48,534 (11.2) | 6,523 (11.1) | 42,011 (11.2) | |
| O Levels/GCSEs or equivalent | 115,671 (26.6) | 14,990 (25.6) | 100,681 (26.7) | |
| None of the above | 77,499 (17.8) | 11,192 (19.1) | 66,307 (17.6) | |
| Smoking status, N (%) | < 0.001 | |||
| Never | 238,470 (54.8) | 31,480 (53.7) | 206,990 (55.0) | |
| Previous | 151,644 (34.9) | 21,250 (36.2) | 130,394 (34.6) | |
| Current | 44,926 (10.3) | 5,905 (10.1) | 39,021 (10.4) | |
| BMI (kg/m2), Mean (SD) | 27.41 (4.78) | 28.26 (5.37) | 27.28 (4.67) | < 0.001 |
| BMI category, N (%) | < 0.001 | |||
| Normal (<25) | 144,476 (33.2) | 16,885 (28.8) | 127,591 (33.9) | |
| Overweight (25∼30) | 184,782 (42.5) | 23,863 (40.7) | 160,919 (42.8) | |
| Obesity (30∼) | 105,782 (24.3) | 17,887 (30.5) | 87,895 (23.4) | |
| Vitamin D concentrations (nmol/L), Mean (SD) | 48.32 (19.66) | 47.03 (19.52) | 48.52 (19.67) | < 0.001 |
| Vitamin D concentrations (nmol/L)a, N (%) | < 0.001 | |||
| 12.8–32.6 | 108,839 (25.0) | 15,966 (27.2) | 92,873 (24.7) | |
| 32.7–46.8 | 109,258 (25.1) | 14,993 (25.6) | 94,265 (25.0) | |
| 46.9–62.0 | 108,744 (25.0) | 14,279 (24.4) | 94,465 (25.1) | |
| 62.1–104.0 | 108199 (24.9) | 13397 (22.8) | 94802 (25.2) | |
| Vitamin D category (nmol/L), N (%) | < 0.001 | |||
| Deficient (<25) | 55,438 (12.7) | 8,378 (14.3) | 47,060 (12.5) | |
| Insufficient (25∼50) | 186,302 (42.8) | 25,697 (43.8) | 160,605 (42.7) | |
| Optimal (>50) | 193,300 (44.4) | 24,560 (41.9) | 168,740 (44.8) | |
| Vitamin D supplements, N (%) | 7,899 (1.8) | 1,124 (1.9) | 6,775 (1.8) | 0.048 |
| FEV1 (mL), Mean (SD) | 2,829 (800) | 2,596 (804) | 3,562 (1,107) | < 0.001 |
| FVC (mL), Mean (SD) | 3,735 (1,063) | 2,862 (793) | 3,760 (1,054) | < 0.001 |
| FEV1/FVC (%), Mean (SD) | 75.9 (7.3) | 73.0 (8.6) | 76.3 (7.0) | < 0.001 |
| Current wheeze, N (%) | 36,204 (61.7) | |||
| At least one asthma hospitalizationb, N (%) | 29,496 (50.3) |
aThese data were divided by quartiles.
bHospitalization for asthma was defined as ever having had a hospitalization with a main diagnosis compatible with asthma, excluding hospitalizations with a main diagnosis consistent with COPD.