Table 2

Distribution of selected host characteristics by case–control status in Chinese
Variables Case (n = 384) Control (n = 384) P*
Age, y (mean ± SD) 62.4 ± 10.8 61.5 ± 12.1 0.277
Gender, no. (%)
Male 222 (57.8) 217 (56.5) 0.715
Female 162 (42.2) 167 (43.5)
Smoking status, no. (%)
Never 228 (59.4) 218 (56.8) 0.738
Former 70 (18.2) 72 (18.7)
Current 86 (22.4) 94 (24.5)
Pack-years (mean ± SD) 32.7 ± 25.1 30.3 ± 27.7 0.209
Tumor grade, no. (%)
I 41 (10.7) 0
II 176 (45.8) 0
III 86 (22.4) 0
IV 81 (21.1) 0

*P values were derived from the χ2 test for categorical variables (gender and smoking status) and t test for continuous variables (age and pack-years).

Zhao et al.

Zhao et al. BMC Cancer 2012 12:617   doi:10.1186/1471-2407-12-617

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