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Table 1 Characteristics of age, gender and smoking status of cases and controls

From: Polymorphisms of XRCC1 genes and risk of nasopharyngeal carcinoma in the Cantonese population

Variable Cases(n= 462) Controls (n= 511)
Gender   
Male 339 (73.4)a 252 (49.1)
Female 123 (26.6)a 259 (50.9)
Age range (yr)   
   <60 395 (85.5)b 422 (82.6)
   ≥60 67 (14.5)b 89 (17.4)
Mean age in years (S. D.) 45.9 (12.2) 45.7 (15.6)
Smoking status a   
   No 164 (35.5)c 353 (69.1)
   Yes 298 (64.5)c 158 (30.9)
Pack-years smoked   
   <20 103 (34.6)d 70 (44.3)
   ≥20 195 (65.4)d 88 (55.7)
Mean pack-years smoked (S.D.) 16.1 (17.2) 22.8 (17.3)
Median pack-years smoked (S.D.) 20 (15.6) 20 (17.3)
  1. a P = 0.0000, χ2 = 58.85; b P = 0.22, χ2 = 1.53; c P = 0.0000, χ2 = 109.77; d P = 0.04, χ2 = 4.15