HRs (95% CIs) for incident rheumatoid arthritis according to passive smoking in childhood, overall and after stratified by ever-smoking status among women in the E3N cohort (N=79 806)
| Cases, no/person-years, no | Model 1 HR (95% CI) | Model 2 HR (95% CI) | |
| All population (N=79 806) | |||
| Passive smoking in childhood | |||
| No | 584/1 640 298 | Reference | Reference |
| Yes | 114/257 284 | 1.26 (1.03 to 1.54) | 1.24 (1.01 to 1.51) |
| P value | 0.023 | 0.037 | |
| Never smokers (N=43 170) | |||
| Passive smoking in childhood | |||
| No | 293/900 764 | Reference | Reference |
| Yes | 57/124 998 | 1.42 (1.07 to 1.88) | 1.40 (1.06 to 1.86) |
| P value | 0.016 | 0.019 | |
| Ever smokers (N=36 636) | |||
| Passive smoking in childhood | |||
| No | 291/739 535 | Reference | Reference |
| Yes | 57/132 286 | 1.11 (0.83 to 1.47) | 1.10 (0.83 to 1.46) |
| P value | 0.48 | 0.50 | |
| All population (N=79 806) | |||
| Never smoker, no passive smoking in childhood | 293/900 764 | Reference | Reference |
| Never smoker, passive smoking in childhood | 57/124 998 | 1.41 (1.06 to 1.88) | 1.38 (1.04 to 1.83) |
| Ever smoker, no passive smoking in childhood | 291/739 535 | 1.27 (1.08 to 1.50) | 1.26 (1.07 to 1.49) |
| Ever smoker, passive smoking in childhood | 57/132 286 | 1.41 (1.06 to 1.87) | 1.37 (1.03 to 1.82) |
Model 1: adjusted for age (as the timescale).
Model 2: adjusted for age (as the timescale), active smoking status (current smoker, non-smoker, former smoker, except for stratified analyses and combined analysis), passive smoking in adulthood, body mass index (kg/m²) (<18.5 kg/m², 18.5–25 kg/m², 25–30 kg/m², ≥30 kg/m²), and educational level (<high school, up to two-level university, three/four-level university).
P for interaction between smoking status and passive smoking during childhood=0.28.
E3N, Etude Epidémiologique auprès des femmes de la Mutuelle générale de l’Education Nationale.