1. General characteristics
Our sample had 70 cases of ALL and 60 controls and aged (0–4) years. The case group had 42 males and 28 females and the control group had 36 males and 24 females (Table 1). Control groups were hospital inpatients that were randomly selected. This results were patients from departments of gastroenterology (12 patients), urology (9 patients), metabolic and neonatology (4 patients), ENT for tonsillectomy and middle-ear tube insertion (7 patients), minor surgeries such as foreign body ingestion (6 patients), neurology (4 patients), infection (8 patients), asthma (9 patients), and endocrinology (1 patient).
There was no statistical significant difference in feeding habits when comparing patients who had infections and other presentations and when comparing all presentations P = 0.663 and P = 0.605 respectively. Sixty-nine cases and 60 controls were validated for complications of delivery with 68 cases and 57 controls born with no complications. Sixty-seven cases and 59 controls were validated for place of living. Twenty-three cases and 26 controls were from major cities and their suburbs in Syria (Damascus, Rif-Dimashq, and Aleppo), 17 cases and nine controls from Homs and Hama, 13 cases and 15 controls from Al-Jazira region in Syria (Deir ez-Zur, Ar Raqqah and Al Hasakah), eight cases and six controls from southern Syria (Daraa, As Suwayda and Quneitra), three cases and one control from the Syrian coast (Latakia and Tartus), and three cases and two controls were from Idlib (Table 1).
Sixty cases were exclusively breastfed until 6 months of age (Group A), 8 needed additional infant formula (Group B) and 2 relied only on infant formula (Group C). In comparison, 41 controls were exclusively breastfed (Group A), 6 required additional formula feeding (Group B) and 13 relied only on infant formula (Group C).
2. Breastfeeding exposure
A. Case-control groups:
There was a statistically significant difference between Group A and Group B + C when comparing cases and controls (OR, 2.78; 95% CI, 1.174–6.588). It was also statistically significant between Group A + B and Group C when comparing cases and controls (OR, 1.10; 95% CI, 0.35–3.40). However, the authors did not find a statistically significant difference when comparing Group A and Group B in cases and controls (P > 0.05).
In contrast, there was a statistically significant difference when we compared children of Group B and Group C among cases and controls (OR, 8.67; 95% CI, 1.40-53.85). Overall, ALL incidence was increased in children who were breastfed in comparison with infant formula (Table 2). When excluding patients with any parent of low educational level, we had 24 cases and 22 controls.
We found no statistical significant difference when comparing cases and controls with all any of BF groups P > 0.05. No significant difference found when comparing case and control groups with educational levels P > 0.05.
Comparison of Characteristics between Breastfed children and relying on Infant formula is demonstrated in (Table 3).In case-control population, a statistically significant difference was found between having a father with low and medium educational level with Group A and Group B + C, with Group A being associated with a lower educational level of the father (OR, 2.83; 95% CI, 1.11–7.17). This was also the case for the mother when compared with the same groups, but the result was insignificant (P = 0.0569). Statistically significant differences were found between having a father or a mother with low educational level and medium educational level with Group A and Group B, with Group A having a higher incidence for a father with low educational level (OR, 5,65; 95% CI, 1.41–22.71), and for a mother with low educational level (OR, 6.44; 95% CI, 1.34–31.05).
Moreover, when comparing Group A with B, we found no statistically significant difference when compared with mothers with medium educational level and high educational level P = 0.1, and when comparing Group B and C, there was not a statistically significant difference (P = 0.0737), with Group C having higher incidence for low educational level mothers.
Moreover, we found a higher incidence of positive family history in subjects with low educational level mothers when compared to medium educational level mothers (P = 0.0290). However, we found no statistically significant difference when comparing having a positive family history with being breastfed overall.
In summary, in the case group we found that gender, having consanguineous parents, being born with complications, having positive CD10, ALL type, FAB classification, prognostic risk, or having a family history for malignancies do not have a statistically significant difference when compared with Group A, Group B, or Group C (P > 0.05). However, having a mother with a low educational level was significantly correlated with a higher incidence of EBF in comparison to a higher educational level when comparing Group A with Group B (OR = 8.8; 1.01–76.71).
3. Sub-analysis:
The mean number of siblings for all patients was 3.77 (SD ± 2.222), with 3.81 (SD ± 0.278) for cases and 3.72 (SD ± 0.286) for controls. There was no statistical significant difference between case and control groups in the method of delivery when comparing C-section and normal delivery P = 0.410. There was also no was no statistical significant difference between Group A and Group B + C or Group A + B and Group C when compared with normal delivery and C-section P = 0.471 and P = 0.118 respectively. No statistical difference was found when comparing cases and controls by gender, complications of delivery, educational level of parents, city of origin, and number of siblings (P > 0.05).