Table 1.
Baseline characteristics (at urine collection in 2000) of breast cancer cases (n=555), including by MT1R subtype (n=158), and matched controls (n=799)
| Characteristic | Controls (n=799) | All breast cancer cases (n=555) | MT1R negative cases (n=91) | MT1R positive cases (n=67) |
|---|---|---|---|---|
| Mean melatonin level, in ng/mg creatinine (SD) | 29.8 (30.7) | 26.6 (25.9) | 29.1 (28.7) | 24.2 (34.0) |
| Mean age, in years (SD) a | 66.9 (6.8) | 66.6 (6.8) | 67.4 (7.1) | 66.9 (6.5) |
| Mean age at menarche, in years (SD) | 12.6 (1.4) | 12.5 (1.4) | 12.6 (1.3) | 12.4 (1.4) |
| Mean age at menopause, in years (SD) | 49.6 (4.7) | 50.3 (5.0) | 50.4 (4.3) | 50.5 (4.7) |
| Mean number of births (SD) | 3.2 (1.6) | 3.1 (1.4) | 3.2 (1.5) | 3.1 (1.3) |
| Family history of breast cancer, % | 16 | 23 | 23 | 21 |
| Mean BMI, in kg/m2 (SD) | 26.4 (5.2) | 26.8 (5.0) | 26.8 (4.7) | 27.3 (4.8) |
| Mean alcohol intake, in g/day (SD) | 5.3 (8.5) | 6.3 (9.8) | 5.8 (9.1) | 6.8 (11.8) |
| Current smoker, % | 4 | 6 | 9 | 3 |
| History of benign breast disease, % | 59 | 65 | 63 | 60 |
| Recent PMH use, % a | 56 | 66 | 73 | 66 |
| Duration of PMH use (estrogen only), % | ||||
| None | 58 | 63 | 54 | 72 |
| <5 years | 13 | 10 | 11 | 15 |
| ≥5 years | 29 | 27 | 35 | 13 |
| Duration of PMH use (estrogen + progesterone), % | ||||
| None | 62 | 54 | 56 | 52 |
| <5 years | 15 | 14 | 6 | 15 |
| ≥5 years | 23 | 32 | 38 | 33 |
| First morning urine, % | 95 | 93 | 97 | 97 |
| ER+/PR+ tumor, % | n/a | 74 | 78 | 75 |
a
These are matching factors.
SD=standard deviation