Table 2. Characteristics of populations.

	Population 1			Population 2
	case (n = 808)	control (n = 829)	P value	case (n = 463)	control (n = 458)	P value
age (year)	60.36±10.22	61.12±12.01	0.166	54.06±8.76	53.27±9.06	0.175
male	634 (78.5%)	647 (78.0%)	0.837	335 (72.4%)	332 (72.5%)	0.963
BMI (kg/m2)	25.70±3.28	24.97±3.08	<0.001	25.56±3.26	24.20±2.89	<0.001
smoking	367 (45.4%)	111 (13.4%)	<0.001	269 (58.1%)	232 (50.7%)	<0.001
Hypertension	528 (65.3%)	311 (37.5%)	<0.001	294 (63.5%)	118 (25.8%)	<0.001
diabetes mellitus	225 (27.8%)	104 (12.5%)	<0.001	125 (27.0%)	30 (6.6%)	<0.001
hyperlipidemia	439 (54.3%)	521 (62.8%)	<0.001	314 (67.8%)	181 (39.5%)	<0.001
Metabolic syndrome	272 (33.7%)	163 (19.7%)	<0.001	142 (30.7%)	50 (10.9%)	<0.001

The data were presented as mean±SEM (standard error of the mean) for age and BMI as well as No.(percentage) for other factors. P values for age and BMI were calculated from t-test comparing case and control groups within population. P values for gender, smoking, hypertension, diabetes mellitus, hyperlipidemia, metabolic syndrome were calculated from Chi-square test within population. BMI: body mass index.