Table 1. Distribution of 965 cases of cancers of the upper aerodigestive tract and 1779 controls, and the corresponding ORs with 95% CI, according to various measures of aspirin use. Italy, 1992–2000.

	Cases	Controls	OR (95% CI)a
Nonusers	928	1692	1b
Regular users	37	87	0.89 (0.56–1.43)
Duration of usec (years)
<5	29	45	1.46 (0.82–2.57)
⩾5	7	40	0.33 (0.13–0.82)
Time since first use (years)
<5	23	32	1.68 (0.87–3.27)
⩾5	14	55	0.51 (0.26–0.99)

^aEstimates from unconditional logistic regression adjusted for sex, age, centre, education, tobacco smoking and alcohol drinking.

^bReference category.

^cThe sum does not add up to the total because of some missing values.