Risks of ever asthma among adolescents from the schools of Louvain-la-Neuve and Bastogne-Lessines (both Belgium) without parental asthma and having attended an indoor pool for <500 h according to their lifetime outdoor pool attendance and their total serum IgE level
| Outdoor pool attendance h | Total serum IgE | |||||||||
| <25 kIU·L−1 | >25 kIU·L−1 | >50 kIU·L−1 | >100 kIU·L−1 | |||||||
| Range | Median# | OR (95% CI) | p-value | OR (95% CI) | p-value | OR (95% CI) | p-value | OR (95% CI) | p-value | |
| Louvain-la-Neuve¶ | 0 | 0 | 1.0 (1.0–1.0) | 1.0 (1.0–1.0) | 1.0 (1.0–1.0) | 1.0 (1.0–1.0) | ||||
| >0–100 | 35 | 1.77 (0.14–22.5) | 0.86 | 0.69 (0.03–14.3) | 0.81 | 0.74 (0.04–14.8) | 0.85 | 0.85 (0.05–15.5) | 0.91 | |
| >100–500 | 280 | 0.80 (0.06–10.5) | 0.84 | 11.7 (1.11–124) | 0.04 | 10.9 (1.07–110) | 0.54 | 10.9 (1.13–106) | 0.04 | |
| >500 | 860 | 0.81 (0.11–6.0) | 0.20 | 17.7 (1.51–207) | 0.02 | 16.1 (1.41–184) | 0.03 | 17.7 (1.60–196) | 0.02 | |
| Bastogne | 0 | 0 | 1.0 (1.0–1.0) | 1.0 (1.0–1.0) | 1.0 (1.0–1.0) | 1.0 (1.0–1.0) | ||||
| and | >0–100 | 45 | 0.0 (0–ND) | 1.0 | 1.77 (0.38–8.20) | 0.46 | 2.51 (0.48–13.2) | 0.28 | 3.00 (0.50–18.4) | 0.22 |
| Lessines+ | >100–500 | 200 | 0.0 (0–ND) | 1.0 | 2.10 (0.56–7.9) | 0.27 | 2.58 (0.61–10.9) | 0.04 | 3.67 (0.76–17.9) | 0.11 |
| >500 | 725 | 0.0 (0–ND) | 1.0 | 3.9 (0.82–18.6) | 0.09 | 4.76 (0.87–26.0) | 0.07 | 12.8 (1.69–97.8) | 0.01 | |
Ig: immunoglobulin; OR: odds ratio; CI: confidence interval;. #: These values correspond to the adolescents without parental asthma and with a cumulated indoor chlorinated pool attendance <500 h. ¶: n = 285; +: n = 262. The numbers of subjects among referents (OR 1.00) and the three pool attendance categories were as follows. Louvain-la-Neuve: total population: 78, 72, 90 and 45; serum IgE <25 kIU·L−1: 25, 15 , 33 and 11; serum IgE >25 kIU·L−1: 53, 57, 57 and 34; serum IgE >50 kIU·L−1: 40, 42, 46 and 27; serum IgE >100 kIU·L−1: 27, 29, 29 and 16. Bastogne-Lessines: total population: 133, 46, 57 and 26; serum IgE <25 kIU·L−1: 48, 19, 14 and 10; serum IgE >25 kIU·L−1: 85, 27, 43 and 16; serum IgE >50 kIU·L−1: 61, 18, 34 and 13; serum IgE >100 kIU·L−1: 39, 15, 23 and 6. ORs were adjusted for the presence of mould on bedroom walls, the only predictor entering in the model at p<0.20 (no adjustment was made for serum IgE, as that was the stratification criterion).