Aim: Prolonged breastfeeding was shown to reduce the risk of childhood acute leukemia. The aim of the study was to investigate the protective effect of longer breastfeeding on the risk of lymphoid malignancies in children and its dependent socio-economic factors.
Methods: The study group comprised of 169 patients with acute lymphocytic leukemia (ALL), Hodgkin's (HL) and non-Hodgkin's lymphoma (NHL), age =or<15 years, and 169 healthy controls, matched to patients by age and sex. Mothers of all study subjects provided information via telephone about the history of breastfeeding and parameters seen as proxies for viral infection.
Results: The mean age+/-SD of cases was 5.44+/- 3.29 years and of control subjects 5.51+/-3.62 years. The male/female ratio was 1.73. Overall, the mean number of months of breastfeeding in the male patients and controls was 9.1 (95% confidence interval [CI] 7.9-10.4) and 12.1 (95% CI 11.0-13.4), respectively (P<0.001), and in the female patients and controls 8.4 (95% CI 6.9-10.1) and 11.5 (95% CI 10.0-13.0), respectively (P<0.01). In 103 ALL patients, a shorter period of breastfeeding (0-6 months duration), was associated with increased odds ratio (OR) for males (OR=3.1, 95% CI 1.4-6.8) and females (OR=2.2, 95% CI 0.8-6.32) as compared to breastfeeding longer than 6 months. In 103 ALL patients, 32 HL and 34 NHL patients, there were no statistically significant differences in the duration of breastfeeding between the male and female patients and their respective controls. In multivariate analysis, statistically significant risk factors for the development of childhood lymphoid malignancy were: a shorter duration of breastfeeding, lower age and level of education of mother and higher income, larger size of accommodation and birth order in the family.
Conclusion: The current study confirmed that a longer duration of breastfeeding has protective effect against ALL and HL. Additional factors found to be associated with an elevated risk of lymphoid malignancy were low age and low education of mother. All these factors can be related to an increased risk of early childhood infections.