Effects of cohort affiliation (active female hairdressers and referents, respectively) and smoking on incidence rate ratio (IRR) (95% CI) of asthma
| Smoking | ||||
|---|---|---|---|---|
| Never | Ever | |||
| Cohort affiliation | Incidence (/1000) | IRR* (95% CI) | Incidence (/1000) | IRR* (95% CI) |
| *IRRs are adjusted for calendar year (1970–80, 1981–90, and 1991–96), hay fever (no/yes), and region (south/middle-north). | ||||
| Referents | 2.5 | 1.0 (–) | 3.7 | 1.6 (1.2 to 2.2) |
| Hairdressers | 4.4 | 1.6 (1.1 to 2.2) | 3.4 | 1.5 (1.0 to 2.1) |