Table 4.

Adjusted^a Relative Risks and 95% Confidence Intervals of Invasive Colon Cancer, by Baseline Status of Menopausal Hormone Therapy Use, for Selected Potential Effect Modifiers, Among Perimenopausal and Postmenopausal Participants in the California Teachers Study, 1995–2006

	No. of Cases	Baseline Status of HT Useb						Ptrend	Phomogeneity
		Baseline- Never HT User		Baseline- Former HT User		Baseline- Recent HT User
		Relative Riska	95% Confidence Interval	Relative Riska	95% Confidence Interval	Relative Riska	95% Confidence Interval
Long-term recreational physical activityc
Low	95	1.00	Referent	1.00	0.60, 1.67	0.47	0.29, 0.77	0.003	0.18
Intermediate/high	346	1.00	Referent	0.86	0.64, 1.16	0.70	0.54, 0.89	0.005
Body mass index, kg/m2
<30	340	1.00	Referent	0.78	0.58, 1.01	0.66	0.52, 0.85	0.001	0.49
≥30	84	1.00	Referent	1.29	0.78, 2.14	0.52	0.30, 0.88	0.016
Regular NSAID used
Low	396	1.00	Referent	0.87	0.66, 1.15	0.67	0.53, 0.85	<0.001	0.13
High	36	1.00	Referent	0.86	0.37, 1.95	0.37	0.17, 0.80	0.009
Calcium intake, mge
≤696.8	204	1.00	Referent	0.84	0.57, 1.22	0.59	0.43, 0.82	0.001	0.60
>696.8	191	1.00	Referent	0.82	0.54, 1.23	0.67	0.48, 0.93	0.018
Calcium, mg, + vitamin D, IU, intakea,f
Low	330	1.00	Referent	0.86	0.63, 1.16	0.64	0.50, 0.83	<0.001	0.70
High	65	1.00	Referent	0.67	0.33, 1.35	0.56	0.32, 0.98	0.046
Family history of colorectal cancerg
No	375	1.00	Referent	0.89	0.66, 1.18	0.71	0.56, 0.90	0.005	0.04
Yes	55	1.00	Referent	0.96	0.51, 1.79	0.34	0.17, 0.66	0.001
Personal history of colorectal polypsh
No	392	1.00	Referent	0.93	0.71, 1.22	0.63	0.50, 0.80	<0.001	0.35
Yes	38	1.00	Referent	0.62	0.22, 1.69	0.87	0.40, 1.87	0.848
Smoking historyi
Never smoker	248	1.00	Referent	0.90	0.64, 1.28	0.67	0.49, 0.90	0.007	0.96
Ever smoker	193	1.00	Referent	1.39	0.54, 3.62	0.68	0.27, 1.71	0.385
Alcohol intake, g/dayj
0	141	1.00	Referent	0.92	0.59, 1.46	0.75	0.51, 1.10	0.864	0.34
>0	271	1.00	Referent	0.80	0.57, 1.13	0.60	0.45, 0.79	0.771

Abbreviations: HT, hormone therapy; NSAID, nonsteroidal antiinflammatory drug.

^aAdjusted for race (as shown), body mass index (continuous measure), and physical activity (low, intermediate, high) and stratified by age at cohort entry (continuous measure in years).

^b“HT use” refers to use of any of the following: estrogen therapy only, estrogen + progestin therapy only, and mixed formulations.

^cLong-term recreational physical activity combines strenuous and moderate activity and is defined as low, intermediate, or high average weekly hours of long-term recreational physical activity.

^dRegular NSAID use combines information on aspirin and ibuprofen use. High NSAID use was defined as use ≥4 times per week for more than 4 years; low/no regular NSAID use included all others.

^eCalcium intake (mg) from diet and supplements was cut at the median value for participants in this analysis, 696.8 mg/day.

^fCalcium intake plus vitamin D intake (from diet and supplements) was dichotomized as highest quartile for both calcium and vitamin D versus all others.

^gA positive family history of colorectal cancer was defined as colon or rectal cancer in at least 1 first-degree relative (mother, father, sister or brother).

^hSelf-reported personal history of colon or rectal polyps (not cancer) was categorized as no, yes, or unknown.

ⁱFor analyses of effect modification, smoking was categorized as never smoker or ever smoker.

^jFor analyses of effect modification, alcohol intake was categorized as 0 g/day or >0 g/day.