Table 2.
Estimated differencesa (95% confidence interval) in square-root-transformed percent mammographic density for a 10-μg/m3 PM increase
| Across the United States | Northeast | Midwest | West | South | p for region interaction term | |
|---|---|---|---|---|---|---|
| Premenopausal | ||||||
| 1 year prior | n = 1624 | n = 577 | n = 554 | n = 261 | n = 232 | |
| PM2.5 | 0.04 (–0.17, 0.26) | 0.06 (–0.40, 0.52) | –0.08 (–0.58, 0.43) | 0 (–0.35, 0.34) | 0.21 (–0.32, 0.74) | 0.59 |
| PM2.5–10 | –0.01 (–0.16, 0.15) | –0.01 (–0.57, 0.54) | –0.07 (–0.42, 0.28) | 0.08 (–0.19, 0.34) | –0.34 (–0.95, 0.27) | 0.45 |
| PM10 | 0.01 (–0.10, 0.12) | 0.02 (–0.26, 0.30) | –0.06 (–0.33, 0.20) | 0.03 (–0.14, 0.20) | –0.05 (–0.57, 0.47) | 0.58 |
| 3-year average | n = 1624 | n = 582 | n = 554 | n = 260 | n = 228 | |
| PM2.5 | 0.05 (–0.16, 0.27) | 0.05 (–0.40, 0.51) | –0.05 (–0.55, 0.45) | –0.01 (–0.36, 0.35) | 0.27 (–0.27, 0.81) | 0.53 |
| PM2.5–10 | 0 (–0.15, 0.16) | 0.02 (–0.53, 0.57) | –0.04 (–0.40, 0.33) | 0.10 (–0.18, 0.38) | –0.58 (–1.19, 0.03) | 0.22 |
| PM10 | 0.02 (–0.10, 0.13) | 0.02 (–0.25, 0.30) | –0.03 (–0.30, 0.23) | 0.04 (–0.13, 0.20) | –0.17 (–0.70, 0.36) | 0.67 |
| Postmenopausal | ||||||
| 1 year prior | n = 1634 | n = 738 | n = 360 | n = 274 | n = 262 | |
| PM2.5 | –0.04 (–0.26, 0.19) | 0.37 (–0.03, 0.77) | –0.24 (–0.91, 0.42) | –0.21 (–0.56, 0.13) | –0.05 (–0.70, 0.60) | 0.09 |
| PM2.5–10 | –0.01 (–0.16, 0.14) | 0.22 (–0.24, 0.69) | 0.11 (–0.38, 0.60) | –0.22 (–0.47, 0.03) | 0.32 (–0.32, 0.96) | 0.29 |
| PM10 | –0.01 (–0.12, 0.10) | 0.19 (–0.05, 0.42) | –0.01 (–0.34, 0.32) | –0.14 (–0.29, 0.02) | 0.19 (–0.35, 0.74) | 0.15 |
| 3-year average | n = 1634 | n = 745 | n = 364 | n = 272 | n = 253 | |
| PM2.5 | –0.05 (–0.27, 0.17) | 0.39 (–0.02, 0.79) | –0.25 (–0.91, 0.42) | –0.27 (–0.62, 0.07) | 0.06 (–0.61, 0.73) | 0.06 |
| PM2.5–10 | –0.01 (–0.16, 0.14) | 0.19 (–0.27, 0.65) | 0.16 (–0.32, 0.64) | –0.23 (–0.47, 0.02) | 0.39 (–0.30, 1.07) | 0.24 |
| PM10 | –0.02 (–0.13, 0.09) | 0.18 (–0.06, 0.41) | 0.02 (–0.31, 0.34) | –0.15 (–0.31, 0.01) | 0.31 (–0.26, 0.89) | 0.10 |
PM particulate matter, PM 2.5 particulate matter less than 2.5 μm in diameter, PM 2.5–10 particulate matter between 2.5 and 10 μm in diameter, PM 10 particulate matter less than 10 μm in diameter
aAdjusted for cohort, age, body mass index, parity and age at first birth categories, hormonal therapy use, history of biopsy-confirmed benign breast disease, and date of mammogram