Table 7. Risk of Acute Myeloid Leukemia Associated with Maternal Vitamin and Folic Acid Supplementation, Stratified by Study with Low or High Between-Study Variabilitya.
| Supplement, Period |
All Studies | Low Between-study Variabilityb | High Between-study Variabilityc | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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| Data Availability | No. Controls |
No. Cases |
Model 1d | Model 2e | No. Controls |
No. Cases |
Model 1d | Model 2e | No. Controls |
No. Cases |
Model 1d | Model 2e | |||||||||
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| No. Studies |
No. Controls |
No. Cases |
OR | (95% CI) | OR | (95% CI) | OR | (95% CI) | OR | (95% CI) | OR | (95% CI) | OR | (95% CI) | |||||||
| Vitamins | |||||||||||||||||||||
| Any time | 8 | 7534 | 562 | ||||||||||||||||||
| Nof | 4144 | 317 | 1.00 | 1.00 | 2448 | 192 | 1.00 | 1.00 | 1696 | 125 | 1.00 | 1.00 | |||||||||
| Yes | 3390 | 245 | 0.95 | (0.80–1.14) | 0.92 | (0.75–1.14) | 2324 | 163 | 1.01 | (0.80–1.26) | 1.00 | (0.79–1.28) | 1066 | 82 | 1.06 | (0.77–1.46) | 0.75 | (0.47–1.18) | |||
| Preconception | 5 | 3448 | 297 | ||||||||||||||||||
| nof | 2959 | 247 | 1.00 | 1.00 | — | — | — | — | |||||||||||||
| Yes | 489 | 50 | 1.28 | (0.92–1.79) | 0.96 | (0.66–1.39) | |||||||||||||||
| Pregnancy | 6 | 4638 | 367 | ||||||||||||||||||
| nof | 2477 | 198 | 1.00 | 1.00 | 811 | 78 | 1.00 | 1.00 | 1666 | 120 | 1.00 | 1.00 | |||||||||
| Yes | 2161 | 169 | 1.02 | (0.82–1.26) | 0.85 | (0.64–1.14) | 1804 | 151 | 0.84 | (0.63–1.13) | 0.88 | (0.63–1.25) | 357 | 18 | 0.69 | (0.41–1.16) | 0.75 | (0.44–1.25) | |||
| Folic acid | |||||||||||||||||||||
| Any time | 6 | 4078 | 331 | ||||||||||||||||||
| nof | 2964 | 264 | 1.00 | 1.00 | 1460 | 167 | 1.00 | 1.00 | 1504 | 97 | 1.00 | 1.00 | |||||||||
| Yes | 1114 | 67 | 0.73 | (0.55–0.97) | 0.68 | (0.48–0.96) | 439 | 41 | 0.86 | (0.59–1.26) | 0.86 | (0.58–1.27) | 675 | 26 | 0.67 | (0.42–1.07) | 0.35 | (0.18–0.68) | |||
| Preconception | 5 | 3510 | 303 | ||||||||||||||||||
| nof | 3131 | 266 | 1.00 | 1.00 | — | — | — | — | |||||||||||||
| Yes | 379 | 37 | 1.19 | (0.82–1.73) | 0.88 | (0.59–1.32) | |||||||||||||||
| Pregnancy | 5 | 3593 | 260 | ||||||||||||||||||
| nof | 2825 | 226 | 1.00 | 1.00 | 1317 | 129 | 1.00 | 1.00 | 1508 | 97 | 1.00 | 1.00 | |||||||||
| Yes | 768 | 34 | 0.61 | (0.41–0.90) | 0.52 | (0.31–0.89) | 106 | 8 | 0.81 | (0.38–1.71) | 0.85 | (0.40–1.80) | 662 | 26 | 0.67 | (0.42–1.08) | 0.36 | (0.18–0.71) | |||
Studies were separated into low- and high-variability groups, based on proportions of women taking vitamins or folic acid across each of the studies, when between-study variability contributed to more than 30% of the overall variability. Based on this criteria, studies were not stratified for the preconception time period.
Low-variability studies: Vitamins, any time: canada, Costa Rica, US NCCLS (1995–2002), greece, australia, egypt; Vitamins, pregnancy: canada, Costa Rica, Greece, Australia, US NCCLS (2003–2008), egypt; Folic acid, pregnancy: New Zealand, Brazil, US NCCLS (2003–2008)
High-variability studies: Vitamins, any time: Brazil, France, US NCLS (2003–2008); Vitamins, pregnancy: Brazil, France; Folic acid, any time: Costa Rica, France; Folic acid, pregnancy: Costa Rica, France
Pooled OR adjusted for age, sex, ethnicity, and parental education
Pooled OR adjusted for age, sex, ethnicity, parental education, and study
Refererence category