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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