Changing population characteristics, effect-measure modification, and cancer risk factor identification

Table 4 Relative risk of colon cancer associated with NSAID/aspirin and HRT use, and their interaction, among post-menopausal women only, 1991–1994

		All post-menopausal women		NSAID/aspirin Use Stratified
		Cases/Controls (N)	Adjusted	Case/Control (N)		Yes	No
			OR (95% CI)	Yes	No	OR¹ (95% CI)	OR¹ (95% CI)
HRT use	Yes	138/198	1.0	52/89	86/109	1.0	1.3 (0.8–2.0)
HRT use	No	344/361	1.4 (1.0–1.8)	90/136	254/225	1.1 (0.7–1.7)	2.0 (1.3–2.9)
RERI² (95% CI);p value							(-0.03, 1.21);0.06

¹Adjusted for age, energy intake, physical activity level, BMI, dietary calcium and fiber and NSAIDs/aspirin.
²Relative excess risk for interaction, a measure of the amount of effect-measure modification on the additive scale. A value of zero would represent no difference in ORs.