Characteristics of the study population
| Characteristics | Cohort | Non-asthmatic | Asthmatic | Mean difference (95% CI) | OR (95% CI) | p-value |
| Subjects n | 245 | 149 | 96 | |||
| Demographics | ||||||
| Age years | 35.8±4.8 | 35.8±4.8 | 35.7±4.9 | −0.06 (−1.30–1.18) | 0.925 | |
| BMI kg·m−2 | 23.8±4.4 | 24.0±4.5 | 23.5±4.1 | −0.45 (−1.57–0.67) | 0.427 | |
| FEV1 L | 3.12±0.4 | 3.21±0.4 | 2.98±0.4 | −0.24 (−0.35–−0.13) | <0.001 | |
| FEV1# % pred | 97.1±0.05 | 100.2±0.05 | 92.5±0.06 | −0.04 (−0.05–0.02) | <0.001 | |
| FEV1/FVC# % | 80.9±0.07 | 82.0±0.03 | 79.2±0.11 | −0.02 (−0.03–0.003) | 0.109 | |
| Former smoker % | 112 (45.9) | 63 (42.3) | 49 (51.0) | 1.42 (0.85–2.38) | 0.191 | |
| Single/lesbian in population¶ % | 38 (15.5) | 26 (17.4) | 12 (12.5) | 0.68 (0.32–1.41) | 0.367 | |
| Asthma markers | ||||||
| Log FeNO+ ppb | 1.05±0.3 | 1.03±0.2 | 1.09±0.3 | 0.06 (−0.01–0.12) | 0.093 | |
| Allergy | 99 (40.4) | 39 (26.2) | 60 (62.5) | 4.70 (2.71–8.16) | <0.001 | |
| Log RDR methacholine | 0.25±0.7 | −0.08±0.5 | 0.73±0.7 | 0.82 (0.67–0.97) | <0.001 | |
| % AHR to methacholine | 35.9 | 10.1ƒ | 76.0 | |||
| Log RDR mannitol§ | −1.64±0.8 | −1.56±0.8 | −2.21±0.5 | 0.65 (0.11–1.15) | 0.012 | |
| % AHR to mannitol§ | 34.6 | 0 | 41.4 | |||
| ACQ score | 0.21±0.4 | 0.07±0.1 | 0.43±0.5 | 0.36 (0.28–0.45) | <0.001 | |
| Serum IL levels | ||||||
| IL-6, pg·mL−1 | 1.22±1.4 | 1.19±1.5 | 1.26±1.3 | 0.07 (−0.28–0.43) | 0.694 | |
| hsCRP mg·L−1 | 1.90±4.9 | 1.603±3.0 | 2.33±7.0 | 0.70 (−0.57–1.98) | 0.276 | |
| TNF pg·mL−1 | 0.82±0.6 | 0.79±0.6 | 0.85±0.7 | 0.05 (−0.10–0.21) | 0.502 | |
| IL-8 pg·mL−1 | 4.29±3.0 | 4.18±2.0 | 4.47±4.0 | 0.29 (−0.47–1.06) | 0.447 | |
| IL-10 pg·mL−1 | 0.19±0.4 | 0.18±0.4 | 0.20±0.4 | 0.05 (−0.09–0.12) | 0.720 | |
| Log ECP μg·L−1 | 0.94±0.4 | 0.90±0.4 | 1.0±0.3 | 0.09 (0.00–0.18) | 0.049 | |
| Log IgE kU·L−1 | 1.35±0.6 | 1.20±0.5 | 1.60±0.6 | 0.40 (0.26–0.54) | <0.001 | |
| Fertility treatment mean % | ||||||
| Stimulated cycles | 0.47 (1.5) | 0.34 (1.2) | 0.68 (1.7) | 0.33 (−0.04–0.71) | 0.081 | |
| IUI | 4.7 (3.9) | 4.7 (3.8) | 4.8 (4.0) | 0.16 (−0.85–1.16) | 0.762 | |
| IVF | 2.87 (3.4) | 2.73 (3.1) | 3.10 (3.8) | 0.36 (−0.51–1.24) | 0.415 | |
| ICSI | 0.34 (1.4) | 0.32 (1.3) | 0.37 (1.5) | 0.04 (−0.31–0.40) | 0.813 | |
| Donor oocyte | 0.05 (0.28) | 0.06 (0.3) | 0.02 (0.1) | −0.04 (−0.11–0.03) | 0.273 |
Data are presented as mean±sd or n (%) unless otherwise stated. Data in bold is statistically significant. BMI: body mass index; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; FeNO: exhaled nitric oxide fraction; RDR: response dose ratio; AHR: airway hyperresponsiveness; ACQ: asthma control questionnaire; IL: interleukin; hsCPR: high sensitivity C-reactive protein; TNF: tumour necrosis factor; ECP: eosinophil cationic protein; IUI: intrauterine insemination; IVF: in vitro fertilisation; ICSI: intra cytoplasmic sperm injection. #: p-values and mean differences were calculated in log values; ¶: relationship was defined as single/lesbian or heterosexual; +: geometric mean; §: mannitol test was performed only on patients with AHR to methacholine; ƒ: all non-asthmatics with a post metacholine test had negative mannitol tests.