Table 1. Characteristic distribution of the study population.

	LHID 2005					LHID 2000
	Case		Control			Case		Control
	N	%	N	%	P 1	N	%	N	%	p 1
Total	2514		10056			2370		9480
Age
<40	325	12.9	1300	12.9	Matched	292	12.3	1,165	12.3	Matched
40–45	342	13.6	1367	13.6		316	13.3	1,271	13.4
45–50	463	18.4	1849	18.4		440	18.6	1,764	18.6
50–55	410	16.3	1643	16.3		386	16.3	1,535	16.2
55–60	289	11.5	1154	11.5		308	13.0	1,232	13.0
> = 60	685	27.2	2743	27.3		628	26.5	2,513	26.5
Index year
2002–2004	634	25.2	2536	25.2	Matched	649	27.4	2,596	27.4	Matched
2005–2007	883	35.1	3532	35.1		780	32.9	3,120	32.9
2008–2010	997	39.7	3988	39.7		941	39.7	3,764	39.7
Occupation
Civil servants, teachers, governmental or private business employees, professionals, and technicians	1,452	57.8	5,593	55.6	<0.01	1,346	56.8	5,407	57.0	<0.01
Farmers or fishermen	277	11.0	1,608	16.0		284	12.0	1,414	14.9
Low income families supported by social welfare or veterans, or supported by another family member	785	31.2	2,855	28.4		740	31.2	2,659	28.0
Number of screen tests
0	9,663	384.4	2,286	22.7	<0.01	9,128	385.1	2,175	22.9	<0.01
1	338	13.4	196	1.9		290	12.2	162	1.7
> = 2	55	2.2	32	0.3		62	2.6	33	0.3
Average ambulatory visit per year
≤6	371	14.8	1,755	17.5	<0.01	359	15.1	1,907	20.1	<0.01
6–12	585	23.3	2,434	24.2		574	24.2	2,267	23.9
12–24	878	34.9	3,450	34.3		835	35.2	3,138	33.1
>24	680	27.0	2,417	24.0		602	25.4	2,168	22.9

¹ Chi-square test or Fisher’s exact test if any number in a cell is less than five.