Number of incident asthma cases and adjusted relative risk(RR) for incident asthma by body mass index (BMI) group and for three-unit increase in BMI, stratified by smoking#
| <20 | 20–24.9 | 25–29.9 | 30–34.9 | ≥35 | Increase in BMI | |||||||
| n (%) | RR (95% CI) | n (%) | RR (95% CI) | n (%) | RR (95% CI) | n (%) | RR (95% CI) | n (%) | RR (95% CI) | n (%) | RR (95% CI) | |
| Never-smokers¶ | 28 (2.0) | 0.9 (0.6–1.4) | 390 (1.9) | Ref | 456 (2.6) | 1.5 (1.3–1.7) | 153 (4.0) | 2.2 (1.8–2.7) | 61 (7.0) | 3.5 (2.6–4.5) | 1088 (2.5) | 1.27 (1.22–1.32) |
| Ex-smokers¶ | 11 (2.1) | 0.7 (0.4–1.3) | 313 (2.6) | Ref | 346 (2.9) | 1.2 (1.0–1.4) | 127 (4.6) | 1.9 (1.6–2.4) | 39 (6.7) | 2.6 (1.9–3.7) | 836 (3.0) | 1.22 (1.16–1.28) |
| Current smokers¶ | 102 (5.0) | 1.1 (0.9–1.3) | 840 (4.0) | Ref | 710 (4.7) | 1.3 (1.2–1.4) | 196 (6.1) | 1.6 (1.4–1.9) | 47 (7.5) | 1.7 (1.3–2.3) | 1895 (4.5) | 1.14 (1.10–1.18) |
| All+ | 141 (3.6) | 1.0 (0.9–1.2) | 1543 (2.9) | Ref | 1512 (3.4) | 1.3 (1.2–1.4) | 476 (4.9) | 1.8 (1.6–2.0) | 147 (7.1) | 2.4 (2.0–2.9) | 3819 (3.4) | 1.19 (1.17–1.22) |
BMI group ranges are shown in kilogrammes per metre squared. CI: confidence interval; Ref: reference group. #: 5,491 individuals were excluded because of missing data for one or more of the variables adjusted for; ¶: adjusted for sex, age (year of birth), education, physical activity, disability pension and rural/urban status; +: additionally adjusted for smoking category.