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Table 1 Distribution of 815 cases of NPC and 1502 controls by demographics, putative risk factors of NPC, and factors related to dietary fiber intake in Hong Kong, China, 2014–2017

From: Dietary fiber intake from fresh and preserved food and risk of nasopharyngeal carcinoma: observational evidence from a Chinese population

Variable NPC cases (N = 815) Controls (N = 1502) P-value‡
n % n %  
Mean socioeconomic status score (SD)ǂ 3 2.8 3.7 3.0 < 0.001
Family history of cancer      < 0.001
 None 288 35.3 753 50.1  
 Yes, but not NPC 269 33.0 561 37.4  
 Yes, NPC 134 16.4 77 5.1  
 Don’t know 124 15.2 111 7.4  
Exposure to any occupational hazards      < 0.001
 Never 285 35.0 758 50.5  
 Ever 399 49.0 597 39.8  
 Don’t know 131 16.1 147 9.8  
Smoking      < 0.001
 Never 417 51.2 945 62.9  
 Ever 392 48.1 552 36.8  
 Refuse to answer 6 0.7 5 0.3  
Alcohol drinking      0.19
 Never 512 62.8 977 65.1  
  ≤ 210 g/week 203 24.9 377 25.1  
  > 210 g/week 100 12.3 148 9.9  
EBV VCA-IgA†      < 0.001
 Seronegative 56 10.8 902 88.1  
 Seropositive 463 89.2 122 11.9  
Sources of dietary fiber intake, g/week
Fresh
  Green leafy vegetables      0.001
    < 9.2 327 40.1 502 33.4  
   9.2- < 17.2 384 47.1 731 48.7  
   17.2- < 52 93 11.4 250 16.6  
   Don’t know/missing 11 1.4 19 1.3  
  Other vegetables      0.013
    < 2.2 475 58.3 831 55.3  
   2.2- < 5.5 175 21.5 340 22.6  
   5.5- < 24 119 14.6 377 18.4  
   Don’t know/missing 46 5.6 54 3.6  
  Carrot      < 0.001
    < 0.6 318 39.0 521 34.7  
   0.6- < 2.4 199 24.4 402 26.8  
   2.4- < 34 132 16.2 361 24.0  
   Don’t know/missing 166 20.4 218 14.5  
  Tomato      < 0.001
    < 1.9 366 44.9 618 41.2  
   1.9- < 4.7 331 40.6 629 41.9  
   4.7- < 40 43 5.3 156 10.4  
   Don’t know/missing 75 9.2 99 6.6  
  Citrus      0.006
    < 0.6 218 26.8 344 22.9  
   0.6- < 6.7 339 41.6 583 38.8  
   6.7- < 29 73 9.0 189 12.6  
   Don’t know/missing 185 22.7 386 25.7  
  Fruits other than citrus      < 0.001
    < 2.2 379 46.5 574 38.2  
   2.2- < 3.0 216 26.5 439 29.2  
   3.0- < 32 159 19.5 394 26.2  
   Don’t know/missing 61 7.5 95 6.3  
Soybean products
Tofu      0.015
   < 1.2 362 44.4 603 40.2  
  1.2- < 4.0 330 40.5 639 42.5  
  4.0- < 51 70 8.6 182 12.1  
  Don’t know/missing 53 6.5 78 5.2  
Soymilk      0.18
   < 0.2 180 22.1 366 24.4  
  0.2- < 0.4 229 28.1 437 29.1  
  0.4- < 11 211 25.9 396 26.4  
  Don’t know/missing 195 23.9 303 20.2  
Bean curd, servings/week      0.53
   < 0.1 313 38.4 563 37.5  
  0.1- < 0.2 181 22.2 359 23.9  
  0.2- < 10 190 23.3 366 24.4  
  Don’t know/missing 131 16.1 214 14.3  
Preserved vegetables, servings/week      0.28
   < 0.5 275 33.7 512 34.1  
  0.5- < 2.7 211 25.9 437 29.1  
  2.7- < 44 225 27.6 385 25.6  
  Don’t know/missing 104 12.8 168 11.2  
Preserved fruits, servings/week      0.15
   < 0.3 348 42.7 666 44.3  
  0.3- < 0.7 88 10.8 196 13.1  
  0.7- < 33 157 19.3 285 19.0  
  Don’t know/missing 222 27.2 355 23.6  
Condiments, servings/week      0.022
   < 0.5 260 31.9 552 36.8  
  0.5- < 2.2 283 34.7 456 30.4  
  2.2- < 24 211 25.9 408 27.2  
  Don’t know/missing 61 7.5 86 5.7  
  1. Abbreviation: NPC Nasopharyngeal carcinoma; SD Standard deviation; g Gram; EBV VCA-IgA, IgA against Epstein-Barr virus viral capsid antigen VCA
  2. ‡ t-test and Chi-square test were used to compare the mean of continuous factors, and proportions of categorical factors between cases and controls, respectively
  3. ǂ Socioeconomic status score ranged from −1 (lowest socioeconomic status) to 13 (highest socioeconomic status), and was calculated by the subject’s, and his/her father’s and mother’s education, personal income, household income and housing type at age 10
  4. † Epstein-Barr virus viral capsid antibody (EBV VCA-IgA) levels: optical density value < 1.2 (seronegative) or ≥ 1.2 (seropositive)