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Table 1 Subject characteristics by case and control groups

From: Combined and interaction effect of chlamydia pneumoniae infection and smoking on lung cancer: a case-control study in Southeast China

Variables Cases N (%)
(N = 449)
Controls N (%)
(N = 512)
χ2 P
Age (years) 0.194 0.979
 < 45 39 (8.7) 43 (8.4)   
 45 ~ 197 (43.9) 229 (44.7)   
 60 ~ 192 (42.7) 214 (41.8)   
 ≥ 75 21 (4.7) 26 (5.1)   
Sex 3.290 0.070
 Male 293 (65.3) 305 (59.6)   
 Female 156 (34.7) 207 (40.4)   
Ethnicity 0.274 0.601
 Han 443 (98.7) 507 (99.0)   
 Others 6 (1.3) 5 (1.0)   
Education 90.131 < 0.001
 Primary school or less 231 (51.4) 145 (28.3)   
 High school 174 (38.8) 199 (38.9)   
 College or higher 44 (9.8) 168 (32.8)   
Marital status 0.204 0.651
 Married 429 (95.5) 486 (94.9)   
 Unmarried or others 20 (4.5) 26 (5.1)   
Occupation 75.731 < 0.001
 Agriculture, forestry, animal husbandry and fishery personnel 138 (30.7) 80 (15.6)   
 Production transport workers 109 (24.3) 89 (17.4)   
 Enterprises and institutions personnel 123 (27.4) 260 (50.8)   
 Business service personnel 33 (7.4) 58 (11.3)   
 Unemployed or others 46 (10.2) 25 (4.9)   
BMI (kg/m2) 11.815 0.003
 < 18.5 32 (7.1) 20 (3.9)   
 18.5 ~ 278 (61.9) 286 (55.9)   
 ≥ 24.0 139 (31.0) 206 (40.2)   
Smoking 68.114 < 0.001
 No 188 (41.9) 350 (68.4)   
 Yes 261 (58.1) 162 (31.6)   
Passive smoking 48.699 < 0.001
 No 131 (29.2) 263 (51.4)   
 Yes 318 (70.8) 249 (48.6)   
Alcohol consumption 13.787 < 0.001
 No 308 (68.6) 405 (79.1)   
 Yes 141 (31.4) 107 (20.9)   
Tea drinking 1.255 0.263
 No 239 (53.2) 254 (49.6)   
 Yes 210 (46.8) 258 (50.4)   
History of lung diseases 18.235 < 0.001
 No 381 (84.9) 478 (93.4)   
 Yes 68 (15.1) 34 (6.6)   
History of other diseases 5.326 0.021
 No 264 (58.8) 338 (66.0)   
 Yes 185 (41.2) 174 (34.0)   
Family history of cancer 5.070 0.024
 No 336 (74.8) 414 (80.9)   
 Yes 113 (25.2) 98 (19.1)   
Occupational physical activity 52.066 < 0.001
 Light 144 (32.1) 278 (54.3)   
 Median 169 (37.6) 150 (29.3)   
 Heavy 136 (30.3) 84 (16.4)   
Physical exercise 62.254 < 0.001
 Not often 316 (70.4) 231 (45.1)   
 Usually 133 (29.6) 281 (54.9)   
Cooking oil fumes 31.925 < 0.001
 No 84 (18.7) 167 (32.6)   
 Few 231 (51.4) 241 (47.1)   
 Some 106 (23.6) 93 (18.2)   
 Heavy 28 (6.2) 11 (2.1)   
Decoration within ten years 0.646 0.421
 No 278 (61.9) 304 (59.4)   
 Yes 171 (38.1) 208 (40.6)   
Pollution near the residence 27.114 < 0.001
 No 368 (82.0) 476 (93.0)   
 Yes 81 (18.0) 36 (7.0)   
Ventilation status 4.272 0.118
 Bad 11 (2.4) 8 (1.6)   
 General 48 (10.7) 38 (7.4)   
 Well 390 (86.9) 466 (91.0)   
Pathological types
 Adenocarcinoma 277 (61.7)   
 Squamous cell carcinoma 96 (21.4)   
 Adenosquamous carcinoma 7 (1.6)   
 Large cell carcinoma 2 (0.4)   
 Small cell carcinoma 38 (8.5)   
 Others 29 (6.4)