Table 3.
Smoking in relation to percent mammographic density, stratified by parity
| Women without a full-term birth (n = 147) | Women with ≥1 or more full-term births (n = 651) | |||||||
|---|---|---|---|---|---|---|---|---|
| n (%) | Adjusted models Beta estimate (SE)a | p-value | Adjusted mean percent density (95% CI)b | n (%) | Adjusted models Beta estimate (SE)a | p-value | Adjusted mean percent density (95% CI)b | |
| Ever smokers | ||||||||
| Started to smoke within 5 years of menarche | 0.7 | – | 0.2 | |||||
| No | 32 (58) | 0.0 | 43.2 (36.2, 50.3) | 91 (48) | 0.0 | 39.3 (35.8, 42.8) | ||
| Yes | 23 (42) | 2.51 (6.30) | 49.3 (40.7, 57.9) | 100 (52) | −3.40 (2.67) | 36.6 (33.3, 40.0) | ||
| Started to smoke at or before age at first full-term birth (FFTB) | – | 0.2 | ||||||
| Yes | – | – | – | 177 (92) | 0.0 | 38.3 (35.9, 40.7) | ||
| No | – | – | – | 15 (8) | −5.77 (4.93) | 33.4 (24.3, 42.5) | ||
| Age started to smoke, years | 0.9 | – | 0.03 | |||||
| ≥18 | 37 (67) | 0.0 | 46.1 (39.8, 52.5) | 111 (58) | 0.0 | 40.5 (37.5, 43.5) | ||
| <18 | 18 (33) | −1.17 (6.26) | 45.0 (35.6, 54.3) | 81 (42) | −5.69 (2.56) | 34.2 (30.5, 37.9) | ||
| Average cigarettes smoked per day | <0.001 | – | 0.9 | |||||
| ≤9 | 17 (30) | 0.0 | 59.0 (50.9, 67.1) | 60 (31) | 0.0 | 37.7 (33.4, 42.0) | ||
| 10–19 | 15 (27) | −15.48 (6.21) | 45.5 (36.3, 54.8) | 57 (29) | −1.30 (3.20) | 37.7 (33.4, 42.1) | ||
| ≥20 | 18 (32) | −23.83 (5.88) | 37.7 (29.4, 46.0) | 56 (29) | −1.40 (3.31) | 37.4 (32.9, 41.9) | ||
| Years smoked | 0.5 | – | 0.07 | |||||
| ≤17 | 29 (53) | 0.0 | 47.4 (40.0, 54.8) | 95 (50) | 0.0 | 40.1 (36.9, 43.4) | ||
| >17 | 26 (47) | −3.70 (6.06) | 44.0 (36.1, 51.9) | 96 (50) | −4.42 (2.43) | 35.4 (32.1, 38.7) | ||
aParameter estimates for each factor modeled individually, in separate models, and adjusted for age, body mass index, race/ethnicity-study site, age at menarche, alcohol consumption, and oral contraceptive use. SE standard error
bMean values are adjusted for age, body mass index, race/ethnicity-study site, age at menarche, alcohol consumption, and oral contraceptive use. Confidence interval, CI