Characteristics of young patients with untreated intermittent adult-onset asthma who were categorised by the cumulative smoking history (pack-years)
| Cumulative smoking history (pack-years) | P value | |||
| Never (n=156) | 0< pack-years ≤4* (n=55) | >4 pack-years (n=51) | ||
| Age (years) | 26.9±4.7 | 26.9±3.9 | 29.0±2.7 | <0.001 |
| Age at onset (years) | 24.9±5.0 | 23.8±4.5 | 26.9±3.9 | 0.001 |
| Men, n (%) | 35 (22.4) | 15 (27.3) | 24 (47.1) | 0.003 |
| Duration of asthma (months) | 10 (2–36) | 12 (2–60) | 12 (2–36) | 0.448 |
| BMI, kg/m2 | 21.6±3.4 | 22.4±4.5 | 21.9±3.3 | 0.337 |
| Total IgE (IU/mL) | 164 (70–537) | 217 (55–721) | 248 (78–807) | 0.243 |
| Peripheral blood eosinophil (count) | 230 (105–405) | 290 (160–490) | 350 (250–700) | 0.016 |
| Atopy, n (%) | 138 (89) | 47 (86) | 50 (98) | 0.075 |
| Prebronchodilator lung function | ||||
| FEV1 (% predicted) | 96.4±12.6 | 89.9±10.3 | 90.6±15.5 | <0.001 |
| FEV1/FVC ratio | 0.85±0.07 | 0.82±0.08 | 0.80±0.08 | <0.001 |
| FVC (L) | 3.50±0.70 | 3.49±0.83 | 3.82±0.92 | 0.053 |
| FVC (%) | 107±12.7 | 103±17.6 | 106±15.0 | 0.187 |
| FEF25–75 (% predicted) | 76.3±22.4 | 65.0±17.8 | 65.8±23.0 | <0.001 |
| Postbronchodilator lung function | ||||
| FEV1 (% predicted) | 101±14.7 | 96.2±12.2 | 92.4±22.4 | 0.025 |
| FEV1/FVC ratio | 0.89±0.07 | 0.87±0.07 | 0.81±0.10 | <0.001 |
| FEF25–75 (% predicted) | 89.2±21.3 | 80.1±19.9 | 75.5±26.6 | 0.001 |
| ΔFEV1 (%)† | 4.89±12.6 | 7.58±7.90 | 7.78±5.24 | 0.151 |
| HisPC20 (mg/mL) | 2.52 (1.05–4.50) | 1.63 (0.40–3.28) | 1.48 (0.64–2.55) | 0.003 |
Data are presented as means±SD, n (%) or medians (IQRs).
Postbronchodilator FVC is missing value, therefore, the data are not shown.
Results highlighted in bold indicate statistically significant findings.
*Current smokers were stratified on the basis of the median value for each smoking parameter.
†(Postbronchodilator FEV1–prebronchodilator FEV1)/prebronchodilator FEV1(L)×100.
BMI, body mass index; FEF25–75, forced expiratory flow between 25% and 75% of the vital capacity; FEV1, forced expiratory volume in one second; FVC, forced vital capacity; HisPC20, provocative concentration of histamine leading to a decrease in the FEV 1 by >20%.