IRR of pregnancy loss times (counts) from childhood secondhand smoke exposure in female never smokers by negative binominal regression (after PSM)
| IRR (95% CI) | ||||
|---|---|---|---|---|
| N | Crude model | Model 1 | Model 2 | |
| Number of smokers | ||||
| None (reference) | 7782 | 1 | 1 | 1 |
| 1 smoker | 5938 | 1.02 (0.93 to 1.12) | 1.03 (0.94 to 1.14) | 1.03 (0.94 to 1.13) |
| ≥2 smokers | 1844 | 1.18 (1.03 to 1.35)* | 1.21 (1.06 to 1.38)* | 1.20 (1.05 to 1.37)* |
| P for trend | 0.03 | 0.01 | 0.02 | |
| Frequency of exposure | ||||
| None (reference) | 7782 | 1 | 1 | 1 |
| <5 times/week | 1925 | 0.82 (0.71 to 0.95) | 0.84 (0.72 to 0.97) | 0.84 (0.73 to 0.97) |
| ≥5 times/week | 5857 | 1.14 (1.04 to 1.25)* | 1.15 (1.05 to 1.26)* | 1.14 (1.04 to 1.25)* |
| P for trend | 0.007 | 0.004 | 0.006 | |
*p<0.05.
Model 1: Adjusted for age.
Model 2: Adjusted for age, education, past occupational dust exposure, past home fuel exposure, oral contraceptive, adulthood passive smoke exposure, age at first pregnancy and age at first menarche.
IRR, incidence rate ratio; PSM, propensity score matching.