Table 3.
Association between risk of breast cancer by quartile of total 12-hour overnight 6-sulfatoxymelatonin output*
| Group and parameter | Q1 | Q2 | Q3 | Q4 | Ptrend† |
| Urinary aMT6s output per 12 h, μg | <6.5 | 6.5–10.8 | 10.8–16.5 | ≥16.5 | |
| Case subjects with invasive and in situ breast cancer | |||||
| No. of case subjects/No. of control subjects | 56/177 | 37/177 | 45/178 | 40/178 | |
| Simple OR (95% CI)‡ | 1.00 (ref.) | 0.65 (0.41 to 1.04) | 0.79 (0.51 to 1.23) | 0.68 (0.42 to 1.11) | .09 |
| Multivariable OR (95% CI)§ | 1.00 (ref.) | 0.68 (0.42 to 1.11) | 0.84 (0.53 to 1.35) | 0.65 (0.39 to 1.09) | .08 |
| Case subjects with invasive breast cancer | |||||
| No. of case subjects/No. of control subjects | 55/171 | 37/170 | 42/169 | 37/173 | |
| Simple OR (95% CI)‡ | 1.00 (ref.) | 0.67 (0.42 to 1.07) | 0.76 (0.48 to 1.20) | 0.63 (0.39 to 1.04) | .05 |
| Multivariable OR (95% CI)§ | 1.00 (ref.) | 0.70 (0.43 to 1.14) | 0.82 (0.50 to 1.34) | 0.59 (0.35 to 1.00) | .04 |
| Multivariable OR (95% CI)§, adjusted for testosterone | 1.00 (ref.) | 0.69 (0.41 to 1.14) | 0.84 (0.51 to 1.38) | 0.56 (0.33 to 0.97) | .02 |
| Excluding current smokers | |||||
| No. of case subjects/No. of control subjects | 51/158 | 31/133 | 36/138 | 25/148 | |
| Simple OR (95% CI)‡ | 1.00 (ref.) | 0.69 (0.41 to 1.15) | 0.72 (0.44 to 1.20) | 0.44 (0.25 to 0.80) | .004 |
| Multivariable OR (95% CI)§ | 1.00 (ref.) | 0.72 (0.41 to 1.26) | 0.74 (0.42 to 1.29) | 0.40 (0.21 to 0.76) | .002 |
| Multivariable OR (95% CI)§, adjusted for testosterone | 1.00 (ref.) | 0.69 (0.39 to 1.22) | 0.71 (0.40 to 1.26) | 0.38 (0.20 to 0.74) | .001 |
Total 12-hour overnight 6-sulfatoxymelatonin output was the concentration of 6-sulfatoxymelatonin (ng/mL) multiplied by the 12-hour volume (mL). Quartiles are based on the distribution in control subjects. Q = quartile; aMT6s = 6-sulfatoxymelatonin; OR = odds ratio; CI = confidence interval; ref. = referent.
We tested for trends by modeling 6-sulfatoxymelatonin output continuously and calculating the Wald statistic. All statistical tests were two-sided.
Simple conditional logistic regression model adjusting for the matching variables (year of birth, month and year of urine collection, and laboratory batch) was used.
Multivariable conditional logistic regression models were used. Relative risks (expressed as odds ratios) were adjusted for the following breast cancer risk factors: body mass index in six categories (≤21, 21.1–23, 23.1–25, 25.1–27, 27.1–30, or >30 kg/m2), history of benign breast disease (yes or no), family history (mother or sister) of breast cancer (yes or no), smoking history (never, past, or current), age at menarche in three categories (≤13, 14, or ≥15 years), age at menopause in four categories (≤45, 46–49, 50–52, or ≥53 years), alcohol consumption (none or ≤12 or >12 g/day), duration of oral contraceptive use (never or ≤1 or >1 year), duration of hormone replacement therapy use (never or ≤1 or >1 year), parity (nulliparous or 1–2 or ≥3 children), age at first child's birth (<25, 25–27, or ≥28 years), and participant's educational level (≤5, >5 to 8, or >8 years).