Table 4.

Incidence of colorectal cancer after randomization to study aspirin or self-selected initiation of any regular nonsteroidal anti-inflammatory drug use (including study and non-study aspirin) in the Physician’s Health Study

				Age-adjusted		Fully-adjusted*
Duration of regular aspirin or NSAID use after randomization or self-selected initiation	Person-years	Events	IR per 100,000 p-y	RR	95% CI	RR	95% CI
Never	88,616	108	122	1.0	reference	1.0	reference
1 – 5 years	97,286	124	127	1.0	0.7 – 1.3	0.9	0.7 – 1.2
6 – 10 years	103,008	157	152	1.0	0.7 – 1.3	0.9	0.7 – 1.3
More than 10 years	76,915	106	138	0.9	0.6 – 1.2	0.8	0.6 – 1.2

^*Rate ratios and their 95% confidence intervals from time-varying Cox proportional hazards model controlling for all variables presented in table 2: age (continuous, linear and squared), body mass index (continuous), vigorous exercise (5 categories), smoking (never, former, current), alcohol consumption (6 categories), multivitamin use, consumption of fruits and vegetables (servings per day, continuous), as well as history of hypertension, diabetes, coronary artery disease (myocardial infarction, coronary artery bypass grafting, or percutaneous transluminal coronary angioplasty), angina, headache, migraine, peptic ulcer, gastrointestinal bleeding, and gastritis; variables are updated during follow-up whenever possible