Asthma incidence rate ratios (IRRs) with 95% CIs in a cohort of active female hairdressers and in a cohort from the general female population (referents), respectively, obtained from multivariate models
| Hairdressers* | Referents† | |||||||
|---|---|---|---|---|---|---|---|---|
| Variable | Cases | Person-year | Incidence (/1000) | IRR‡ (95% CI) | Cases | Person-year | Incidence (/1000) | IRR‡ (95% CI) |
| *Followed up during active years after certification; †followed up since 18 years of age; ‡IRR from a model with all variables included. | ||||||||
| Calendar year: | ||||||||
| 1970–80 | 6 | 3 477 | 1.7 | 1.0 (—) | 12 | 11 932 | 1.0 | 1.0 (—) |
| 1981–90 | 36 | 11 548 | 3.1 | 1.8 (0.8 to 4.3) | 78 | 27 978 | 2.8 | 2.8 (1.5 to 5.1) |
| 1991–96 | 62 | 11 704 | 5.3 | 3.1 (1.3 to 7.3) | 112 | 24 643 | 4.5 | 4.7 (2.6 to 8.6) |
| Total | 104 | 26 729 | 3.9 | 202 | 64 553 | 3.1 | ||
| Hay fever: | ||||||||
| No | 41 | 20 791 | 2.0 | 1.0 (—) | 65 | 51 104 | 1.3 | 1.0 (—) |
| Yes | 63 | 5 939 | 10.6 | 5.5 (3.7 to 8.1) | 137 | 13 449 | 10.2 | 8.0 (6.0 to 10.8) |
| Smoking: | ||||||||
| Never | 54 | 12 173 | 4.4 | 1.0 (—) | 80 | 31 780 | 2.5 | 1.0 (—) |
| Ever | 50 | 14 556 | 3.4 | 0.9 (0.6 to 1.3) | 122 | 32 773 | 3.7 | 1.6 (1.2 to 2.2) |
| Region: | ||||||||
| South | 48 | 13 983 | 3.4 | 1.0 (—) | 78 | 30 035 | 2.6 | 1.0 (—) |
| Middle-north | 56 | 12 747 | 4.4 | 1.2 (0.8 to 1.8) | 124 | 34 518 | 3.6 | 1.3 (1.0 to 1.8) |