Table 4.

Multivariable-adjusted relative risks (RR) and 95% confidence intervals of breast cancer, according to MT1R subtype, across tertiles of creatinine-standardized urinary melatonin level (n=403 [245 controls, 91 MT1R negative cases, 67 MT1R positive cases])

	Tertiles of urinary melatonin levels (in ng/mg creatinine)
	Tertile 1	Tertile 2	Tertile 3	p-trend	p-heterogeneity
Invasive + in situ cases combined
No. of cases / no. of controls	61 / 77	59 / 74	38 / 94
MT1R negative + positive a	1.00 (ref)	1.01 (0.70–1.47)	0.67 (0.44–1.02)	0.05
No. of cases / no. of controls	32 / 42	35 / 34	24 / 61
MT1R negative b	1.00 (ref)	1.08 (0.64–1.81)	0.60 (0.35–1.06)	0.07	0.88
No. of cases / no. of controls	29 / 35	24 / 40	14 / 33
MT1R positive b	1.00 (ref)	0.95 (0.53–1.70)	0.76 (0.39–1.51)	0.39
Invasive cases only
No. of cases / no. of controls	49 / 64	44 / 57	32 / 73
MT1R negative + positive a	1.00 (ref)	0.98 (0.64–1.50)	0.72 (0.45–1.14)	0.14
No. of cases / no. of controls	29 / 38	29 / 32	23 / 54
MT1R negative b	1.00 (ref)	1.00 (0.57–1.75)	0.65 (0.37–1.17)	0.14	0.57
No. of cases / no. of controls	20 / 26	15 / 25	9 / 19
MT1R positive b	1.00 (ref)	0.88 (0.40–1.95)	0.97 (0.39–2.42)	0.79

^aMultivariable conditional logistic regression model adjusted for the following: age at menarche (<12, 12, 13, ≥14 years), age at menopause (≤45, 46–50, 51–53, ≥54 years), parity (nulliparous, 1–2, 3–4, or ≥5 children), family history of breast cancer (mother or sister: yes, no), BMI (continuous in kg/m²), alcohol intake (0, 1–14.9, ≥15 g/day), smoking status (current: yes, no), history of benign breast disease (yes, no), antidepressant use (current: yes, no), PMH use (current: yes, no), type and duration of PMH use (estrogen only: 0, <5, ≥5 years; estrogen + progesterone: 0, <5, ≥5 years),and first morning urine (yes, no).

^bMultivariable conditional polytomous logistic regression model with same covariates as listed above for conditional logistic regression.