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Table 1 Maternal characteristics associated with dietary nitrate intake, National Birth Defects Prevention Study Controls, 1997-2004

From: Maternal characteristics associated with the dietary intake of nitrates, nitrites, and nitrosamines in women of child-bearing age: a cross-sectional study

  Dietary nitrate intake (mg/day)   Odds ratios and 95% confidence intervalsb
  Quartile 1a Quartile 2 Quartile 3 Quartile 4    
  <27.06 27.07-40.48 40.49-60.60 61.89-809.64 p-value 4th quartile compared to the 1st quartile
  n % n % n % n %   Crude Adjustedc
Race/Ethnicity            
   White non-Hispanic 991 28.4 964 27.6 890 25.5 647 18.5 <0.0001 1.0 1.0
   Black non-Hispanic 130 19.7 119 18.1 167 25.3 243 36.9   2.9 (2.3,3.6) 2.4 (1.7,3.3)
   Hispanic 267 20.6 292 22.6 318 24.6 417 32.2   2.4 (2.0,2.9) 1.4 (1.0,1.9)
   Asian/Pacific Islander 25 14.9 19 11.3 36 21.4 88 52.4   5.4 (3.4,8.5) 4.8 (2.7,8.5)
   Other 34 19.4 51 29.2 39 22.3 51 29.1   2.3 (1.5,3.6) 1.6 (0.89,2.9)
   Missing 6 28.6 7 33.3 2 9.5 6 28.6   --- ---
State/Area of residence            
   Texas 168 24.5 192 27.9 165 24.0 162 23.6 <0.0001 1.0 1.0
   Arkansas 194 27.5 182 25.9 168 23.8 161 22.8   0.86 (0.64,1.2) 0.79 (0.52,1.2)
   California 191 24.5 165 21.2 197 25.3 226 29.0   1.2 (0.92,1.6) 0.98 (0.68,1.4)
   Georgia 129 21.1 127 20.8 165 27.1 189 31.0   1.5 (1.1,2.1) 2.2 (1.4,3.4)
   Iowa 245 37.9 187 28.9 147 22.8 67 10.4   0.30 (0.20,0.40) 0.37 (0.23,1.4)
   Massachusetts 150 20.2 192 25.9 216 29.1 184 24.8   1.3 (0.94,1.7) 2.9 (1.9,4.5)
   New Jersey 103 18.2 122 21.5 152 26.9 189 33.4   1.9 (1.4,2.6) 2.7 (1.7,4.1)
   New York 127 24.2 126 24.0 135 25.8 136 26.0   1.1 (0.80,1.5) 1.8 (1.1,2.8)
   North Carolina 72 24.7 81 27.7 54 18.5 85 29.1   1.2 (0.84,1.8) 1.7 (1.1,2.9)
   Utah 74 28.7 78 30.3 53 20.5 53 20.5   0.74 (0.49,1.1) 0.99 (0.59,1.7)
Dietary folate equivalent (μg/day)            
   <319 725 50.4 422 29.3 202 14.1 89 6.2 <0.0001 1.0 1.0
   319-464.9 351 24.0 463 31.6 416 28.5 233 15.9   5.4 (4.1,7.1) 3.4 (2.5,4.7)
   465-685.5 232 15.9 350 23.9 451 30.9 429 29.3   15.1 (11.5,19.8) 5.5 (4.0,7.6)
   > 685.5 145 10.0 217 15.0 383 26.5 701 48.5   39.4 (29.7,52.3) 7.3 (5.1,10.3)
Maternal household income (dollars annually)            
   ≥50 K 442 24.1 469 25.6 496 27.0 428 23.3 <0.0001 1.0 1.0
   40-49,999 120 28.4 114 27.0 100 23.6 89 21.0   0.77 (0.56,1.0) 0.67 (0.47,0.97)
   30-39,999 138 25.5 153 28.3 134 24.8 116 21.4   0.87 (0.66,1.1) 0.71 (0.50,1.0)
   20-29,999 180 24.2 203 27.2 182 24.4 180 24.2   1.0 (0.81,1.3) 0.71 (0.52,0.97)
   10-19.999 165 22.9 167 23.1 189 26.2 201 27.8   1.3 (0.98,1.6) 0.49 (0.36,0.68)
   < 10,000 233 25.2 205 22.1 198 21.4 290 31.3   1.3 (1.0,1.6) 0.43 (0.32,0.59)
   Missing 175 28.4 141 22.9 153 24.8 148 24.0   --- ---
Maternal education (years at school)            
   16+ 436 23.8 465 25.5 483 26.4 445 24.3 0.0010 1.0 ---
   13-15 399 25.9 393 25.5 377 24.5 371 24.1   0.91 (0.75,1.1) ---
   12 394 27.4 361 25.1 338 23.5 345 24.0   0.86 (0.71,1.0) ---
   9-11 171 15.7 166 15.2 361 33.1 393 36.0   1.1 (0.82,1.3) ---
   0-8 46 16.7 60 21.7 71 25.7 99 35.9   2.1 (1.5,3.1) ---
   Missing 7 24.1 7 24.1 7 24.1 8 27.7   --- ---
Dietary Fat (% of daily calories)            
   ≤ 30% 768 23.8 762 23.5 828 25.7 870 27.0 <0.0001 1.0 ---
   >30% 685 26.6 690 26.7 624 24.2 582 22.5   0.75 (0.65,0.87) ---
Pre-pregnancy BMI            
   Normal weight (18.5 < 25.0) 67 21.3 81 25.8 82 26.1 84 26.8 0.6610 1.0 ---
   Under weight (<18.5) 813 25.9 775 24.7 783 25.0 765 24.4   1.3 (0.55,1.9) ---
   Over weight (25.0 < 30.0) 315 25.3 305 24.5 325 26.1 299 24.0   1.0 (0.84,1.2) ---
   Obese (≥30.0) 215 24.2 241 27.2 212 23.9 219 24.7   1.1 (0.88,1.3) ---
   Missing 43 18.9 50 21.9 50 21.9 85 37.3   --- ---
Folic acid containing supplements            
   No 687 26.4 617 23.7 617 23.7 678 26.2 0.0070 1.0 ---
   Yes 758 23.9 828 26.0 827 26.0 765 24.1   1.0 (0.88,1.2) ---
   Missing 8 25.0 7 21.9 8 25.0 9 28.1   --- ---
Multivitamin use            
   No 876 24.6 905 25.4 898 25.2 885 24.8 0.7780 1.0 ---
   Yes 568 25.6 546 24.6 548 24.7 558 25.1   0.97 (0.84,1.3) ---
   Missing 9 36.0 1 4.0 6 24.0 9 36.0   --- ---
Maternal age at conception (years)            
   20-24 409 30.5 328 24.5 306 22.9 296 22.1 <0.0001 1.0 ---
   <20 241 29.3 213 25.8 189 23.0 180 21.9   1.0 (0.80,1.3) ---
   25-29 371 23.8 410 26.3 382 24.5 397 25.4   1.5 (1.2,1.8) ---
   30-34 304 21.3 364 25.6 390 27.3 368 25.8   1.7 (1.4,2.1) ---
   35+ 128 19.4 137 20.7 185 28.0 211 31.9   2.3 (1.8,2.9) ---
  1. a Referent category is nitrate intake at the lowest quartile of intake (27.06 mg.day)
  2. b Only presented for variables included in the final multinomial logistic regression model
  3. c Adjusted for tertiles of daily caloric intake, race/ethnicity, state of residence, maternal household income, and dietary folate as dietary folate equivalents.
  4. Note: p-value excludes missing values
  5. Note: missing categories contain refuse, don't know, and missing