Table 2—

Standardized incidence ratios (SIRs) and 95% confidence intervals (CIs) of lung cancer among asthma patients according to selected characteristics of the cohort

	Males			Females			Total
	Obs	SIR	95% CI	Obs	SIR	95% CI	Obs	SIR	95% CI
Total	492	1.51	1.38–1.65	221	1.78	1.55–2.03	713	1.58	1.47–1.70
Duration of follow-up
1–4 yrs	274	1.99	1.76–2.24	110	2.32	1.91–2.80	384	2.07	1.87–2.29
5–9 yrs	130	1.31	1.10–1.56	61	1.62	1.24–2.08	191	1.40	1.20–1.61
≥10 yrs	88	0.99	0.79–1.22	50	1.27	0.94–1.68	138	1.08	0.90–1.27
Test for linear trend^#		<0.01			<0.01			<0.01
Calendar year at entry
1965–1974	117	1.15	0.95–1.38	41	1.29	0.93–1.75	158	1.18	1.01–1.38
1975–1984	226	1.59	1.39–1.81	83	1.54	1.23–1.91	309	1.57	1.40–1.76
1985–1994	149	1.81	1.53–2.13	97	2.50	2.03–3.05	246	2.03	1.79–2.30
Test for linear trend^#		<0.01			<0.01			<0.01
Age at entry
20–44	13	0.87	0.46–1.49	16	1.27	0.72–2.06	29	1.05	0.71–1.51
45–59	122	1.19	0.99–1.43	67	1.53	1.19–1.94	189	1.30	1.12–1.49
≥60	357	1.71	1.54–1.90	138	2.03	1.70–2.39	495	1.79	1.63–1.95
Test for linear trend^#		<0.01			0.02			<0.01
Other diagnoses at index hospitalization
Asthma as only diagnosis	189	1.24	1.07–1.43	89	1.43	1.15–1.76	278	1.29	1.14–1.45
Asthma as main diagnosis	128	1.62	1.35–1.93	53	1.76	1.32–2.30	181	1.66	1.43–1.92
Asthma as secondary diagnosis	175	1.86	1.59–2.15	79	2.47	1.95–3.08	254	2.01	1.77–2.27
Dept of index hospitalization
Internal/respiratory medicine	392	1.41	1.27–1.56	177	1.67	1.43–1.93	569	1.48	1.36–1.61
Other	100	2.09	1.70–2.55	44	2.42	1.76–3.25	144	2.18	1.84–2.57
Number of hospitalizations during first year of follow-up
1	348	1.66	1.49–1.85	149	1.81	1.53–2.12	497	1.70	1.56–1.86
2–3	110	1.30	1.06–1.56	55	1.70	1.28–2.21	166	1.41	1.21–1.65
≥4	33	1.04	0.72–1.46	17	1.77	1.03–2.83	50	1.21	0.90–1.59
Test for linear trend^#		<0.01			0.78			<0.01
Presence of emphysema
No	486	1.51	1.38–1.65	219	1.78	1.55–2.03	705	1.59	1.47–1.71
Yes	6	1.22	0.45–2.66	2	1.65	0.20–5.95	8	1.31	0.56–2.58
Presence of chronic bronchitis
No	301	1.20	1.07–1.34	150	1.42	1.20–1.67	451	1.27	1.15–1.39
Yes	191	2.54	2.19–2.93	71	3.76	2.93–4.74	262	2.79	2.46–3.15
Histological type of lung cancer
Squamous cell carcinoma	233	1.83	1.61–2.09	81	3.22	2.56–4.00	314	2.06	1.84–2.30
Adenocarcinoma	66	1.11	0.86–1.41	43	0.99	0.71–1.33	109	1.06	0.87–1.27
Small cell carcinoma*	17	1.90	1.11–3.05	15	3.18	1.78–5.25	32	2.34	1.60–3.31

Obs: observed
^#: p-value
*: follow-up 1987–1994