Table 5.

Colorectal adenomas by age at first OC among 73,058 NHS participants.

Age at first OC use (yrs)	Never	13-19	20-24	25-29	30-34	35+
	N cases OR (95% CI)a						test for trend p
Colorectal adenoma	2,981	190	836	877	588	618
	ref.	0.99 (0.85, 1.15)	1.02 (0.93, 1.12)	1.06 (0.98, 1.16)	1.05 (0.95, 1.15)	1.08 (0.99, 1.18)	0.04
Subsites
Proximal colon	1,309	80	396	404	262	281
	ref.	0.95 (0.75, 1.19)	1.07 (0.93, 1.23)	1.09 (0.96, 1.23)	1.05 (0.91, 1.20)	1.15 (1.00, 1.31)	0.04
Distal colon	1,536	94	384	441	297	315
	ref.	0.97 (0.78, 1.20)	0.96 (0.84, 1.10)	1.07 (0.96, 1.21)	1.04 (0.92, 1.18)	1.05 (0.93, 1.19)	0.29
Rectum	556	35	133	145	108	107
	ref.	0.98 (0.69, 1.39)	0.89 (0.70, 1.12)	0.96 (0.78, 1.18)	1.05 (0.85, 1.29)	1.00 (0.81, 1.23)	0.90
Stage
Non-advanced	1,210	88	415	420	277	245
	ref.	1.07 (0.85, 1.33)	1.06 (0.92, 1.22)	1.13 (1.00, 1.27)	1.16 (1.01, 1.32)	1.10 (0.96, 1.27)	0.01
Advanced	1,228	69	266	302	218	263
	ref.	0.93 (0.73, 1.19)	0.93 (0.79, 1.10)	1.01 (0.88, 1.16)	1.01 (0.87, 1.17)	1.10 (0.96, 1.26)	0.41
Multiplicity
1	1,945	123	623	620	399	380
	ref.	0.93 (0.77, 1.12)	1.02 (0.91, 1.14)	1.06 (0.96, 1.17)	1.05 (0.94, 1.18)	1.06 (0.94, 1.18)	0.17
2+	788	52	189	216	150	163
	ref.	1.09 (0.82, 1.45)	1.01 (0.83, 1.23)	1.07 (0.91, 1.27)	1.03 (0.86, 1.24)	1.07 (0.90, 1.27)	0.34

^aAdjusted for age, BMI, height, physical activity, smoking, processed and red meat, folate intake, calcium, total energy intake, aspirin use, HT duration, family history, reason for endoscopy, time period of endoscopy, number of endoscopies, and years since most recent endoscopy.