Table 1 Demographic and clinical characteristics of the study population
Characteristic | Baotou (N = 1170) | Beijing (N = 1232) | P-value |
|---|---|---|---|
Age (years), median (IQR) | 33.0 (25.0–47.0) | 32.0 (28.0–37.0) | 0.097 |
Sex (male/female), n (%) | 584 (49.9%)/586 (50.1%) | 614 (49.8%)/618 (50.2%) | 0.970 |
Course of disease, n (%) |  < 0.001 | ||
  < 1 year | 328 (28.0%) | 221 (18.0%) |  |
 1–5 year | 571 (48.8%) | 636 (51.6%) |  |
 6–10 year | 190 (16.2%) | 269 (21.8%) |  |
  > 10 year | 81 (6.9%) | 106 (8.6%) |  |
Persistent/intermittent, n (%) | 302 (25.8%)/868 (74.2%) | 657 (53.3%)/575 (46.7%) |  < 0.001 |
Mild/moderate to severe, n (%) | 96 (8.2%)/1074 (91.8%) | 223 (18.1%)/1009 (81.9%) |  < 0.001 |
Allergen, n (%) | |||
 Positive/negative | 721 (61.6%)/449 (38.4%) | 808 (65.6%)/424 (34.4%) | 0.044 |
 Outdoor allergens/indoor allergens | 648 (89.9%)/301 (41.7%) | 610 (75.5%)/470 (58.2%) |  < 0.001 |
 With asthma, n (%) | 158 (13.5%) | 89 (7.2%) |  < 0.001 |
 TNSS, median (IQR) | 8.0 (4.0–12.0) | 8.0 (6.0–9.0) |  < 0.001 |