Table 2.

Length of Use of Oral Contraceptives and Cancer in the Shanghai Cohort

Cancer Site	Number of Months of Use	Number of Cases	Number of Person-Years	RR a	95% CI
All Cancers Combined	None	6,669	2,048,373	1.00
	1–11	296	133,981	0.88	0.78, 0.99
	12–59	384	133,176	0.95	0.85, 1.05
	60–119	143	42,602	1.04	0.88, 1.23
	120+	156	42,447	0.99	0.84, 1.16
					p = 0.70
Breast	None	1,496	2,032,357	1.00
	1–11	73	133,492	0.71	0.56, 0.90
	12–59	112	132,404	1.04	0.86, 1.27
	60–119	34	42,318	0.97	0.69, 1.36
	120+	34	42,033	0.94	0.66, 1.32
					p = 0.53
Colon	None	563	2,045,338	1.00
	1–11	25	134,048	0.97	0.64, 1.47
	12–59	32	133,308	0.96	0.67, 1.38
	60–119	13	42,625	1.13	0.65, 1.97
	120+	22	42,378	1.56	1.01, 2.40
					p = 0.16
Liver	None	420	2,047,302	1.00b
	1–11	14	134,154	0.86	0.50, 1.48
	12–59	16	133,451	0.68	0.41, 1.14
	60–119	11	42,639	1.34	0.73, 2.45
	120+	7	42,406	0.67	0.32, 1.44
					p = 0.30
Lung	None	746	2,048,263	1.00
	1–11	25	134,223	0.96	0.64, 1.45
	12–59	29	133,484	0.77	0.53, 1.12
	60–119	14	42,667	1.05	0.62, 1.79
	120+	14	42,417	0.83	0.49, 1.41
					p = 0.29
Ovary	None	254	2,008,845	1.00
	1–11	22	132,754	1.36	0.87, 2.13
	12–59	14	131,891	0.82	0.47, 1.41
	60+	17	84,400	1.44	0.87, 2.39
					p = 0.36
Pancreas	None	208	2,046,309	1.00
	1–11	7	134,161	0.94	0.44, 2.04
	12–59	16	133,439	1.46	0.87, 2.46
	60+	7	85,013	0.81	0.37, 1.74
					p=0.74
Rectal	None	306	2,045,266	1.00
	1–11	11	134,064	0.71	0.37, 1.34
	12–59	29	133,351	1.54	1.04, 2.29
	60–119	12	42,594	1.93	1.08, 3.46
	120+	10	42,373	1.34	0.71, 2.52
					p = 0.017
Stomach	None	721	2,046,890	1.00
	1–11	30	134,167	0.94	0.65, 1.37
	12–59	38	133,390	0.96	0.69, 1.33
	60–119	14	42,610	1.04	0.61, 1.77
	120+	21	42,390	1.32	0.85, 2.05
					p = 0.49
Thyroid	None	141	2,044,687	1.00
	1–11	5	134,094	0.52	0.21, 1.27
	12+	15	218,289	0.99	0.57, 1.72
					p = 0.65
Uterine Corpus	None	236	1,982,639	1.00c
	1–11	14	131,423	1.15	0.65, 2.01
	12+	13	213,962	0.48	0.27, 0.85
					p = 0.015

^aAdjusted for parity and age using linear splines unless otherwise noted

^bAdjusted additionally forever having had a tubal ligation

^cAdjusted additionally for number of induced abortions