Table 4.
Risk of invasive breast cancer associated with outdoor estimates of Light-at-Night among 106,731 study participants: adjusted hazard ratios (HRs) and 95% confidence intervals (95% CI) estimated from Cox proportional hazard models, stratified by menopausal status and relative body weight. a
| Outdoor Light-at-Night Estimates (nanowatts/cm2/sr) | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Lowest Quintilec | Quintile 2 | Quintile 3 | Quintile 4 | Highest Quintile | |||||||
| 0 – 14.2 | 14.3 – 26.4 | 26.5 – 37.4 | 37.5 – 53.3 | 53.4 – 175.2 | |||||||
|
| |||||||||||
| No. casesb | HR (95% CI) | No. cases | HR (95% CI) | No. cases | HR (95% CI) | No. cases | HR (95% CI) | No. cases | HR (95% CI) | Test for (trend) | |
| PREMENOPAUSAL | |||||||||||
| Relative Body Weight | |||||||||||
| BMI < 25 | 142 | 1.0 | 175 | 1.33 (1.03 – 1.73) | 167 | 1.37 (1.05 – 1.80) | 151 | 1.30 (0.98 – 1.72) | 167 | 1.56 (1.16 – 2.08) | 0.02 |
| BMI ≥ 25 | 87 | 1.0 | 86 | 0.94 (0.67 – 1.33) | 83 | 0.92 (0.64 – 1.32) | 80 | 0.91 (0.62 – 1.32) | 98 | 1.06 (0.72 – 1.56) | 0.59 |
| POSTMENOPAUSAL | |||||||||||
| Relative Body Weight | |||||||||||
| BMI < 25 | 341 | 1.0 | 322 | 0.94 (0.79 – 1.12) | 324 | 0.95 (0.80 – 1.14) | 352 | 1.03 (0.86 – 1.24) | 326 | 0.98 (0.80 – 1.18) | 0.82 |
| BMI ≥ 25 | 271 | 1.0 | 273 | 1.06 (0.87 – 1.28) | 277 | 1.07 (0.87 – 1.31) | 272 | 1.02 (0.82 – 1.25) | 295 | 1.11 (0.89 – 1.39) | 0.44 |
adjusted for: age strata (1-year), race/birthplace, family history of breast cancer, age at menarche, pregnancy history, breast feeding history, physical activity, BMI, alcohol consumption, menopausal status and hormone therapy use combination, smoking status, and smoking pack years, neighborhood SES and urbanization.
number of pre-menopausal and post-menopausal cases do not sum to total number of cases because peri-menopausal women were included in total.
reference category