Table 3.
Association Between Acute Lymphoblastic Leukemia and Breastfeeding, Birth Order, and Day Care, Pooled Analyses of 11 Studies (1980–2010), Restricted to Children Aged ≥2 Years, Childhood Leukemia International Consortium
| No. of Studies | ALL |
Controls |
ORa | 95% CI | |||
|---|---|---|---|---|---|---|---|
| No. | % | No. | % | ||||
| Breastfeeding | 11 | 7,399 | 11,181 | ||||
| No | 2,696 | 36.4 | 3,798 | 34.0 | 1.00 | Referent | |
| Yes | 4,639 | 62.7 | 7,264 | 65.0 | 0.95 | 0.89, 1.02 | |
| Missing | 64 | 0.9 | 119 | 1.0 | |||
| <6 months | 2,899 | 39.2 | 4,324 | 38.7 | 1.01 | 0.94, 1.08 | |
| ≥6 months | 1,717 | 23.2 | 2,892 | 25.9 | 0.86 | 0.79, 0.94 | |
| Missing | 87 | 1.2 | 167 | 1.5 | |||
| Breastfeeding duration | |||||||
| 1 month or less | 1,318 | 17.8 | 1,896 | 17.0 | 1.06 | 0.97, 1.16 | |
| 2–4 months | 1,284 | 17.4 | 1,894 | 16.9 | 0.99 | 0.90, 1.08 | |
| 5–7 months | 793 | 10.7 | 1,303 | 11.7 | 0.90 | 0.81, 1.01 | |
| 8–10 months | 439 | 5.9 | 831 | 7.4 | 0.78 | 0.69, 0.89 | |
| 11–13 months | 393 | 5.3 | 690 | 6.2 | 0.83 | 0.72, 0.96 | |
| 14 months or more | 389 | 5.3 | 602 | 5.4 | 0.92 | 0.79, 1.06 | |
| Missing | 87 | 1.2 | 167 | 1.5 | |||
| Birth order | 11 | 7,399 | 11,181 | ||||
| 1 | 3,393 | 45.9 | 4,982 | 44.6 | 1.00 | Referent | |
| ≥2 | 3,944 | 53.3 | 6,119 | 54.7 | 0.94 | 0.88, 1.00 | |
| 2 | 2,500 | 33.8 | 3,872 | 34.6 | 0.95 | 0.88, 1.01 | |
| 3 | 992 | 13.4 | 1,518 | 13.6 | 0.95 | 0.87, 1.05 | |
| 4 | 293 | 4.0 | 485 | 4.3 | 0.86 | 0.73, 1.00 | |
| 5 | 92 | 1.2 | 144 | 1.3 | 0.92 | 0.70, 1.21 | |
| ≥6 | 67 | 0.9 | 100 | 0.9 | 0.93 | 0.68, 1.29 | |
| Missing | 62 | 0.8 | 80 | 0.7 | |||
| P for trend | 0.07 | ||||||
| Day-care center attendance at <1 year of age | 11 | 7,399 | 11,181 | ||||
| No | 6,116 | 82.7 | 8,713 | 77.9 | 1.00 | Referent | |
| Yes | 1,021 | 13.8 | 2,169 | 19.4 | 0.77 | 0.71, 0.84 | |
| Missing | 262 | 3.5 | 299 | 2.7 | |||
| Frequency | 10b | 6,605 | 10,309 | ||||
| Part-time | 553 | 8.4 | 1,416 | 13.7 | 0.75 | 0.67, 0.84 | |
| Full-time | 453 | 6.9 | 737 | 7.1 | 0.79 | 0.70, 0.90 | |
| Missing | 262 | 4.0 | 299 | 2.9 | |||
| Age at start of day-care center attendance | 10c | 7,044 | 10,385 | ||||
| ≥24 months or never | 5,273 | 74.9 | 7,287 | 70.2 | 1.00 | Referent | |
| 14–23 months | 400 | 5.7 | 583 | 5.6 | 1.03 | 0.89, 1.18 | |
| 11–13 months | 200 | 2.8 | 353 | 3.4 | 0.92 | 0.77, 1.10 | |
| 8–10 months | 175 | 2.5 | 342 | 3.3 | 0.82 | 0.68, 0.99 | |
| 5–7 months | 232 | 3.3 | 477 | 4.6 | 0.79 | 0.67, 0.93 | |
| 0–4 months | 506 | 7.2 | 1,086 | 10.5 | 0.75 | 0.66, 0.84 | |
| Missing | 262 | 3.7 | 300 | 2.5 | |||
| P for trend | <0.0001 | ||||||
| Any day care at <1 year of age | 5d | 2,572 | 5,153 | ||||
| No day care | 1,597 | 62.1 | 3,038 | 59.0 | 1.00 | Referent | |
| Child minder and no day-care center | 399 | 15.5 | 686 | 13.3 | 1.02 | 0.88, 1.18 | |
| Day-care center | 487 | 18.9 | 1,340 | 26.0 | 0.71 | 0.63, 0.81 | |
| Missing | 89 | 3.5 | 89 | 1.7 | |||
Abbreviations: ALL, acute lymphoblastic leukemia; AUS_ALL, Australian Study of Causes of Acute Lymphoblastic Leukemia in Children; CA_QCLS, Quebec Childhood Leukemia Study (Canada); CI, confidence interval; FR_ADELE, Adele Study (France); FR_ELECTRE, Electre Study (France); FR_ESCALE, Epidemiologic Study on Childhood Cancer and Leukemia (France); GR_NARECHEM, Nationwide Registration for Childhood Hematological Malignancies (Greece); IT_SETIL, Study on the Etiology of Childhood Lymphohematopoietic Malignancies (Italy); NZ_NZCCS, New Zealand Childhood Cancer Study; OR, odd ratio; UK_UKCCS, United Kingdom Childhood Cancer Study; US_COG15, Children's Oncology Group Study (United States); US_NCCLS, Northern California Childhood Leukemia Study (United States).
a Pooled odds ratio and 95% confidence interval were estimated by unconditional logistic models adjusted for age, sex, study center, maternal education, and maternal age at child's birth.
b AUS_ALL, CA_QCLS, FR_ADELE, FR_ELECTRE, FR_ESCALE, IT_SETIL, NZ_NZCCS, UK_UKCCS, US_COG15, and US_NCCLS.
c CA_QCLS, FR_ADELE, FR_ELECTRE, FR_ESCALE, GR_NARECHEM, IT_SETIL, NZ_NZCCS, UK_UKCCS, US_COG15, and US_NCCLS.
d FR_ADELE, FR_ELECTRE, FR_ESCALE, NZ_NZCCS, and UK_UKCCS.