Table 4.

Remote period dose of aspirin use,^a recent period dose of aspirin use,^b and CRC risk in the pooled NHS and HPFS

Pooled NHS and HPFS	No. of 325-mg aspirin tablets/wk (cumulative mean)				P trend c	Per 2.5-standard tablets/wk increment HR (95% CI)	P trend d
	<0.5	0.5 to <1.5	1.5 to <5	≥5
Remote period dose of aspirin usea
Median values	0	1.00	2.90	7.54	—	—	—
No. of CRC cases (1764 in total)	875	88	531	270	—	—	—
Age-adjusted model, HR (95% CI)e	1 (Reference)	0.77 (0.61 to 0.96)	0.76 (0.68 to 0.85)	0.67 (0.58 to 0.77)	<.001	0.92 (0.89 to 0.95)	<.001
MV-adjusted model, HR (95% CI)f	1 (Reference)	0.77 (0.62 to 0.96)	0.77 (0.69 to 0.87)	0.68 (0.59 to 0.78)	<.001	0.93 (0.90 to 0.96)	<.001
MVf + recent period aspirin useb adjusted model, HR (95% CI)	1 (Reference)	0.78 (0.63 to 0.98)	0.81 (0.72 to 0.91)	0.74 (0.64 to 0.86)	<.001	0.95 (0.92 to 0.98)	.001
Recent period dose of aspirin useb
Median values	0	1.05	2.63	6.25	—	—	—
No. of CRC cases (1764 in total)	820	247	524	173	—	—	—
Age-adjusted model, HR (95% CI)e	1 (Reference)	0.83 (0.72 to 0.96)	0.79 (0.71 to 0.88)	0.69 (0.58 to 0.81)	<.001	0.88 (0.84 to 0.93)	<.001
MV-adjusted model, HR (95% CI)f	1 (Reference)	0.86 (0.74 to 1.00)	0.80 (0.71 to 0.90)	0.68 (0.58 to 0.80)	<.001	0.88 (0.83 to 0.92)	<.001
MVf + remote period aspirin usea adjusted model, HR (95% CI)	1 (Reference)	0.91 (0.79 to 1.06)	0.87 (0.77 to 0.98)	0.76 (0.64 to 0.91)	.001	0.91 (0.87 to 0.97)	.001

^aRemote period dose of aspirin use: cumulative average dose of aspirin use during every specific remote period (>10 years before every follow-up period, ie, began from 1980 [NHS] and 1992 [HPFS] and then was extended by every 2-year subsequent interval at a time until 2002). AHEI = Alternate Healthy Eating Index score; BMI = body mass index; CI = confidence interval; CRC = colorectal cancer; HPFS = Health Professionals Follow-up Study; HR = hazard ratio; MV = multivariable; NHS = Nurses’ Health Study; NSAIDs = nonsteroidal antiinflammatory drugs.

^bRecent period dose of aspirin use: cumulative average dose of aspirin use during every specific subsequent 10-year period after the remote periods.

^cAdjusted for age and follow-up cycle in the follow-up period.

^dAdjusted for age, follow-up cycle, sex, race, pack-years of smoking, physical activity, BMI, alcohol consumption, AHEI, regular use of nonaspirin NSAIDs, family history of CRC, history of diabetes mellitus, screening colonoscopy or sigmoidoscopy in the past 2 years, multivitamin use, total calorie intake, red or processed meat intake, fiber intake, folate intake, calcium intake, and vitamin D intake in the follow-up period.

^e P _trend was calculated using the mid-point of each category of aspirin use in tablets per week.

^f P _trend was the P value for variables modeled as continuous.