Table 2. The characteristics of the study population.

	Cases	Controls
	No. (%)	No. (%)	χ2	P
Total	695	709
Gender			0.570	0.449
Male	406 (58.42)	400 (56.42)
Female	289 (41.58)	309 (43.58)
Age (mean±SD)	60.16±12.26	59.80±13.18		0.598 a
Agegroup			3.625	0.305
≦50	150 (21.58)	154 (21.72)
51–60	207 (29,78)	181 (25.53)
61–70	184 (26.47)	209 (29.48)
≧71	154 (22.16)	165 (23.27)
Smoking Status
Non-Smoker	448(64.65)	499(70.38)	5.257	0.022
Smoker	245(35.35)	210(29.62)

Abbreviations: SD, standard deviation.

^a P value was calculated by the t test.