Table 3.

Case-control analyses stratified by oophorectomy indication (all ages).

	Benign Indication						No Ovarian Indication
Characteristic^a	Bilateral Oophorectomy (n=675)		Control Women (n=675)		Adjusted Odds Ratio (95% Cl)^b	p Value	Bilateral Oophorectomy (n=978)		Control Women (n=978)		Adjusted Odds Ratio (95% Cl)^b	p Value
	N	%	N	%			N	%	N	%
Age at menarche^c
<12	54	8.8	47	8.6	1.00 (reference)	--	93	10.5	88	11.0	1.00 (reference)	--
12	227	37.2	178	32.4	1.02(0.61, 1.69)	0.95	321	36.4	280	35.1	1.21 (0.83, 1.75)	0.33
13	251	41.1	199	36.2	0.91 (0.55, 1.52)	0.72	321	36.4	289	36.3	1.10(0.76, 1.59)	0.61
>13	79	12.9	125	22.8	0.47(0.27, 0.81)	0.007	147	16.7	140	17.6	1.04(0.69, 1.57)	0.84
Oral Contraceptive use (ever vs. never)^d	317	47.0	404	59.9	0.58 (0.46, 0.73)	<0.001	524	53.6	596	60.9	0.71 (0.59, 0.85)	<0.001
Years of oral contraceptive use^c,e
0 or <0.5	358	54.7	271	42.9	1.00 (reference)	--	454	48.9	382	41.5	1.00 (reference)	--
0.5–4.9	158	24.1	130	20.6	0.94(0.70, 1.28)	0.71	244	26.3	219	23.8	0.90(0.71, 1.15)	0.41
≥5.0	139	21.2	231	36.6	0.42(0.31, 0.56)	<0.001	230	24.8	319	34.7	0.56(0.45,0.71)	<0.001
Gravidity^c
0^d	137	20.3	88	13.0	1.00 (reference)	--	116	11.9	139	14.2	1.00 (reference)	--
1	87	12.9	68	10.1	0.81 (0.52, 1.24)	0.32	77	7.9	111	11.3	0.87(0.59, 1.27)	0.47
2	205	30.4	205	30.4	0.59 (0.42, 0.85)	0.004	291	29.8	276	28.2	1.26(0.93, 1.71)	0.13
≥3	246	36.4	314	46.5	0.47 (0.34, 0.66)	<0.001	494	50.5	452	46.2	1.35(1.01, 1.80)	0.04
Twin or multiple qestation^d	16	2.4	14	2.1	1.09(0.52, 2.27)	0.83	26	2.7	19	1.9	1.32(0.73,2.39)	0.37
Pregnancy loss^d	201	29.8	200	29.6	1.03(0.80, 1.31)	0.83	349	35.7	331	33.8	1.11 (0.92, 1.35)	0.28
Induced abortion^{d, f}	35	5.2	50	7.4	0.67(0.42, 1.07)	0.09	57	5.8	68	7.0	0.84(0.58, 1.21)	0.35
Spontaneous abortion or still birthd	174	25.8	171	25.3	1.05(0.81, 1.36)	0.70	314	32.1	283	28.9	1.18(0.97, 1.44)	0.09
Parity^c
0^d	167	24.7	108	16.0	1.00 (reference)	--	146	14.9	171	17.5	1.00 (reference)	--
1	104	15.4	74	11.0	0.91 (0.60, 1.37)	0.65	90	9.2	142	14.5	0.77(0.54, 1.09)	0.15
2	235	34.8	259	38.4	0.54(0.39, 0.75)	<0.001	384	39.3	336	34.4	1.35(1.03, 1.78)	0.03
≥3	169	25.0	234	34.7	0.41 (0.29, 0.58)	<0.001	358	36.6	329	33.6	1.31 (0.99, 1.73)	0.06
Breast feeding	165	34.1	278	52.1	0.40 (0.29, 0.55)	<0.001	328	45.2	377	50.5	0.89(0.70, 1.13)	0.35
Infertility^d	166	24.6	55	8.1	3.77 (2.66, 5.33)	<0.001	126	12.9	109	11.1	1.17(0.89, 1.53)	0.27
Fibrocystic breast disease^d	352	52.1	420	62.2	0.59 (0.46, 0.75)	<0.001	731	74.7	708	72.4	1.14(0.91, 1.42)	0.26
Smoking status^c
Never^d	376	55.7	386	57.2	1.00 (reference)	--	521	53.3	571	58.4	1.00 (reference)	--
Former	143	21.2	140	20.7	0.99(0.75, 1.32)	0.96	250	25.6	237	24.2	1.11 (0.90, 1.38)	0.34
Current	156	23.1	149	22.1	0.94(0.70, 1.26)	0.67	207	21.2	170	17.4	1.34(1.05, 1.72)	0.02
Pack-years^{c, e}
0	376	56.0	386	58.1	1.00 (reference)	--	521	53.5	571	59.8	1.00 (reference)	--
0.1–5.9	78	11.6	65	9.8	1.22(0.84, 1.77)	0.30	102	10.5	102	10.7	1.06(0.78, 1.43)	0.73
≥6.0	217	32.3	213	32.1	0.90(0.70, 1.17)	0.44	350	36.0	282	29.5	1.36(1.11, 1.66)	0.003
Height (cm)^{c, e}
<161.0	189	28.0	207	30.8	1.00 (reference)	--	320	32.7	322	33.0	1.00 (reference)	--
161.0–166.9	255	37.8	259	38.6	1.07(0.81, 1.41)	0.65	347	35.5	320	32.8	1.04(0.83, 1.30)	0.72
≥167.0	231	34.2	205	30.6	1.20(0.90, 1.59)	0.21	311	31.8	333	34.2	0.90(0.71, 1.14)	0.38
Weight (kg)^{c, e}
<64.0	199	29.5	249	37.3	1.00 (reference)	--	256	26.2	324	33.4	1.00 (reference)	--
64.0–78.9	218	32.3	221	33.1	1.22(0.93, 1.61)	0.15	338	34.6	343	35.4	1.25(0.99, 1.57)	0.06
≥79.0	258	38.2	197	29.5	1.56(1.18, 2.07)	0.002	384	39.3	302	31.2	1.62(1.28,2.05)	<0.001
Body mass index (kg/m²)^c
<25.0	275	40.7	294	44.3	1.00 (reference)	--	321	32.8	406	42.0	1.00 (reference)	--
25.0–29.9	177	26.2	197	29.7	0.97(0.74, 1.28)	0.84	304	31.1	291	30.1	1.34(1.08, 1.68)	0.009
≥30.0	223	33.0	173	26.1	1.31 (1.00, 1.71)	0.051	353	36.1	269	27.8	1.70(1.36,2.13)	<0.001

Women with missing or unknown data were not included in the respective analysis for the following characteristics: 467 for age at menarche (64 cases with benign indication and 126 controls; 96 cases with no ovarian indication and 181 controls),171 for years of birth control use (20 cases with benign indication and 43 controls; 50 cases with no ovarian indication and 58 controls); 817 for breast feeding status (191 cases with benign indication and 141 controls; 253 cases with no ovarian indication and 232 controls); 43 for smoking pack-years (4 cases with benign indication and 11 controls; 5 cases with no ovarian indication and 23 controls); and 23 women for height, weight and/or body mass index (0 cases with benign indication and 11 controls; 0 cases with no ovarian indication and 12 controls).

The odds ratios and confidence intervals for each characteristic were calculated using conditional logistic regression models (matched pairs) adjusted for years of education (≤12; 13–16; >16), race (white; non-white) and quartiles of household income (<$42,000; $42,000–56,999; $57,000–71,999; ≥$72,000). Women with unknown education (3 cases with benign indication and 15 controls; 0 cases with no ovarian indication and 20 controls) were assigned to the ≤12 years group, and women with unknown income (3 cases with benign indication and 2 controls; 3 cases with no ovarian indication and 0 controls) were assigned to the $42,000–56,999 group (second quartile).

Ordinal characteristics were also tested for dose-effect (i.e., linear) trends adjusted for years of education, race, and household income: age at menarche (benign indication stratum p<0.001, no ovarian indication stratum p=0.72), years of oral contraceptive use (benign indication stratum p<0.001, no ovarian indication stratum p<0.001), gravidity (benign indication stratum p<0.001, no ovarian indication stratum p=0.006), parity (benign indication stratum p<0.001, no ovarian indication stratum p=0.004), smoking status (benign indication stratum p=0.69, no ovarian indication stratum p=0.02), pack-years (benign indication stratum p=0.51, no ovarian indication stratum p=0.004), height (benign indication stratum p=0.20, no ovarian indication stratum p=0.37), weight (benign indication stratum p=0.002, no ovarian indication stratum p<0.001), and body mass index (benign indication stratum p=0.06, no ovarian indication stratum p<0.001).

For these characteristics, women with missing or unknown data were included in the no exposure category.

Years of oral contraceptive use, smoking pack-years, height, and weight were stratified using tertiles calculated from the overall sample (case-control groups pooled).

We may have underestimated induced abortions performed outside of the medical care facilities included in the REP.