TABLE 4.
Crude associations between methyl donors and other micronutrients involved in one-carbon metabolism and spina bifida stratified by infant sex,1 National Birth Defects Prevention Study (1999–2011)
| Females n = 3851 |
Males n = 3948 |
||||||
|---|---|---|---|---|---|---|---|
| Cases n = 331 | Cont N = 3520 | cOR (95% CI) | Cases n = 380 | Cont N = 3568 | cOR (95% CI) | ||
| Individual nutrients2 | |||||||
| Vitamin B6 | <1.45 mg | 7 | 72 | 1.0 | 13 | 76 | 1.0 |
| ≥1.45 mg | 324 | 3448 | 0.91 (0.42, 2.0) | 367 | 3492 | 0.60 (0.33, 1.1) | |
| Vitamin B12 | <3.5 μg | 19 | 165 | 1.0 | 27 | 169 | 1.0 |
| ≥3.5 μg | 312 | 3355 | 0.79 (0.49, 1.3) | 353 | 3399 | 0.64 (0.42, 0.97) | |
| Betaine | <88 mg | 181 | 1724 | 1.0 | 202 | 1828 | 1.0 |
| ≥88 mg | 150 | 1796 | 0.80 (0.64, 1.0) | 178 | 1740 | 0.93 (0.75, 1.1) | |
| Choline | <200 mg | 24 | 184 | 1.0 | 16 | 190 | 1.0 |
| ≥200 mg | 307 | 3336 | 0.69 (0.45, 1.1) | 364 | 3378 | 1.2 (0.74, 2.1) | |
| Methionine | <2.5 g | 324 | 3461 | 1.0 | 378 | 3506 | 1.0 |
| ≥2.5 g | 7 | 59 | 1.3 (0.62, 2.9) | 2 | 62 | NC | |
| Riboflavin | <2.4 mg | 232 | 2326 | 1.0 | 262 | 2344 | 1.0 |
| ≥2.4 mg | 99 | 1194 | 0.83 (0.65, 1.1) | 118 | 1224 | 0.86 (0.69, 1.1) | |
| Thiamine | <2.34 mg | 325 | 3387 | 1.0 | 363 | 3442 | 1.0 |
| ≥2.34 mg | 6 | 133 | 0.51 (0.23, 1.1) | 17 | 126 | 1.3 (0.78, 2.2) | |
| Zinc | ≤15 mg | 280 | 2985 | 1.0 | 328 | 2983 | 1.0 |
| >15 mg | 51 | 535 | 1.0 (0.75, 1.4) | 52 | 585 | 0.81 (0.60, 1.1) | |
| Number of micronutrients with higher intake2 | |||||||
| 0–1 | 8 | 34 | 1.0 | 8 | 39 | 1.0 | |
| 2–3 | 127 | 1222 | 0.42 (0.19, 0.93) | 153 | 1243 | 0.57 (0.27, 1.2) | |
| ≥4 | 196 | 2264 | 0.35 (0.16, 0.76) | 219 | 2286 | 0.45 (0.21, 0.96) | |
Cont, controls; cOR, crude OR; NC, not calculated.
Excludes n = 66 participants where sex was unknown or ambiguous.
To categorize each micronutrient intake (higher or lower intake), we used a combination of information from diet and supplements. Excluding supplementers, we regressed case-control status on the energy-adjusted dietary estimate of a given methyl donor, using restricted cubic splines with ≤5 knots controlling for estimated dietary folate equivalents as a model covariate, and identified a cut point where the OR comparing higher compared with lower intake was maximized. Subsequently, we grouped the supplementers into the respective higher intake category if the typical content of the supplement was expected to be greater than the identified dietary cutoff (refer to Table 1).