A population-based cohort study of the risk of colorectal and other cancers among users of low-dose aspirin.
Using data from the population-based Prescription Database of North Jutland County and the Danish Cancer Registry, we compared cancer incidence among 29 470 individuals prescribed low-dose aspirin at maximum doses of 150 mg with expected incidence based on county-specific cancer rates, during a 9-year study period. We observed 2381 cancer cases compared with 2187 expected, yielding a standardised incidence ratio (SIR) of 1.09 (95% confidence interval (CI), 1.05-1.13). No apparent risk reductions were found for cancers of the colon (SIR, 0.9; 95% CI, 0.7-1.1) or rectum (SIR, 1.0; 95% CI, 0.8-1.2), or for other site-specific cancers. Increased SIRs were observed for kidney cancer (SIR, 1.4; 95% CI, 1.1-1.7) and brain cancer (SIR, 1.7; 95% CI, 1.3-2.2), although the excess in the latter was confined to the first year of follow-up. Stratification by number of prescriptions and duration of follow-up revealed no apparent trends. The SIR for colorectal cancer was close to unity (SIR, 0.9; 95% CI, 0.6-1.2) among persons with 10 or more prescriptions who were followed for at least 5 years. Our results do not support a major protective effect of low-dose aspirin on the development of colorectal or other cancers. The observed excesses of kidney and brain cancers are not likely to be causally related to the use of low-dose aspirin.
Friis
S
S
Institute of Cancer Epidemiology, Danish Cancer Society, Copenhagen, Denmark. friis@cancer.dk
Sørensen
H T
HT
McLaughlin
J K
JK
Johnsen
S P
SP
Blot
W J
WJ
Olsen
J H
JH
D000368:Aged; D001241:Aspirin / Q000008:administration & dosage*; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000517:prevention & control; D003718:Denmark / Q000453:epidemiology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance; D012307:Risk Factors
D001241:Aspirin