Table 1:

Patient characteristics in centers with low (group A) and high (group B) numbers of cases/hospital

	Group A (n = 171)		Group B (n = 478)		P Value
	No.	%	No.	%	P Value
Sex ratio
Women	122	71.3%	346	72.4%	.80
Men	49	28.7%	132	27.6%
Age
Mean (yr)	52.1 ± 12.2		50.8 ± 11.0		.21
Range (yr)	22–80		23–83
HTA	51/168^a	30.4%	141/468^a	30.1%	.95
Smokers	62/167^a	37.1%	198/470^a	42.1%	.25

a The information was not available in some cases.