Table 3. Relative risks of lung cancer in women using 1 to 2 or 15 or more aspirin tablets per week by duration of use and by latency period between aspirin assessment and lung cancer diagnosis.

	1–2 aspirin tablets per week			⩾15 aspirin tablets per week
Duration of use a	P-Yb	Cases	RRc (95% CId)	P-Yb	Cases	RRc (95% CId)
<2 years	202.5	119	0.86 (0.68–1.07)	27.0	33	1.68 (1.15–2.45)
2–5.9 years	153.8	81	0.87 (0.67–1.14)	21.1	20	1.44 (0.90–2.30)
⩾6 years	69.5	29	0.75 (0.50–1.19)	15.1	11	1.49 (0.81–2.76)
P for trende			0.66			0.31
Latency period f	P-Yg	Cases	RRc (95% CId)	P-Yg	Cases	RRc (95% CId)
0 to <2 yearsh	445.1	234	0.84 (0.70–1.02)	65.6	65	1.55 (1.17–2.06)
2 to <4 years	397.7	238	0.88 (0.73–1.05)	57.8	53	1.24 (0.92–1.68)
4 to <6 years	359.5	240	0.91 (0.76–1.09)	50.3	51	1.19 (0.88–1.62)
6 to <8 years	323.2	256	1.02 (0.86–1.22)	43.2	45	1.15 (0.84–1.59)

Abbreviations: P-Y=person–years; RRs=relative risks; CI=confidence intervals.

^aDuration was calculated as continuous years of aspirin use among current users.

^bP-Y of follow-up, in thousands, from 1980 to 2004.

^cRRs adjusted for age, smoking status, age at start of smoking (past and current smokers), years since quit smoking (past smokers), and cigarettes per day (current smokers).

^d95% CI.

^eP-value for linear trend over median values within categories of years of aspirin use.

^fDuring the latency periods for users of 1–2 aspirin tablets per week, women were censored if they reported ⩾15 tablets per week; during the latency periods for users of ⩾15 aspirin tablets per week, women were censored if they reported 1–2 tablets per week.

^gP-Y of follow-up, in thousands, through 2004 and beginning in 1980 for a latency of 0 to <2 years; in 1982 for a latency of 2 to <4 years; in 1984 for a latency of 4 to <6 years; and in 1986 for a latency of 6 to <8 years.

^hA latency of <2 years is the same as current users in Table 2 because aspirin use was assessed every 2 years.