Longer durations of breastfeeding lowers the risk of childhood cancers

In a recent study published in JAMA Network Open, a Danish team of researchers investigated whether duration of breastfeeding was associated with a lower risk of childhood cancers such as acute lymphoblastic leukemia (ALL).

Study: Exclusive Breastfeeding Duration and Risk of Childhood Cancers. Image Credit: SeventyFour/Shutterstock.com

Background

The incidence of cancer among children below the age of 15 years in Europe is one among every 350, and cancer has the highest rate of disease-related death among children.

Furthermore, although rare mutations in the germline account for 10% of childhood cancers, the causes of these childhood cancers continue to remain unclear.

The most common of these childhood cancers is acute lymphoblastic leukemia. Other common childhood cancers include Hodgkin lymphoma, acute myeloid leukemia, and neuroblastoma.

Recent studies have observed a lower risk of childhood cancers associated with breastfeeding. Pooled studies and meta-analyses have found a 20% lower risk of childhood cancers such as ALL or any other type of leukemia among children who have been breastfed for a minimum of six months.

The role of breastmilk in establishing the infant’s gut microbiome and strengthening the immune system during infancy is well supported.

Furthermore, B-cell precursor ALL has been linked to irregular immune responses, and animal studies have also indicated a connection between the pathogenesis of B-cell precursor ALL and the gut microbiome.

About the study

In the present study, the researchers used data from the health register of the country for a cohort study in which they investigated whether the duration of breastfeeding had an impact on childhood cancer risk.

The study included Danish children born between 2005 and 2018, and the register was used to obtain sociodemographic information on the child and parents.

Additionally, the Medical Birth Register provided data on birth characteristics, while the mother’s education levels were ascertained from the Population Education Register.

The study excluded children with incomplete information on gestational age, birth weight, and mother’s age and education levels.

Additionally, children with Down’s syndrome diagnosed as per the International Statistical Classification of Diseases were also excluded from the study since their distinct biology increases their risk of leukemia.

The register also contained information on breastfeeding, collected during regular home visits by health care nurses throughout the early years of the child’s life. Data on the duration of exclusive breastfeeding, defined as the period during which the infant’s primary source of nutrition consisted of breastmilk, with only water and one milk formula meal a week supplementing the nutrition, was obtained.

The date the child began receiving solid foods or multiple formula meals a week was also obtained to determine the cessation of exclusive breastfeeding.

Children not exclusively breastfed two weeks after birth were classified as ‘never breastfed’ for this analysis. The register also provided information on children with cancer diagnoses between the ages of one and 14 years.

The children were followed up between the ages of one and 15 years or until a cancer diagnosis, death, emigration, follow-up loss, or end of study.

The measured exposure was the duration for which exclusive breastfeeding was the primary source of nutrition for the infant, and the examined outcome was any association between breastfeeding duration and overall childhood cancer risk, as well as childhood cancer risk by subtype.

Results

The results supported previous findings that breastfeeding for longer durations decreased the risk of B-cell precursor ALL.

Children whose primary source of nutrition for the first three months was exclusively breastmilk were at a significantly lower risk of B-cell precursor ALL from age one to 14 years as compared to children who were either never breastfed or were exclusively breastfed for less than three months.

However, the duration of breastfeeding was not found to be associated with the risk of solid or central nervous system tumors in children between the ages of one and 14 years.

B-cell precursor ALL in children is speculated to develop before birth due to an unexplained genetic event that results in preleukemia. Although not all children born with preleukemia develop B-cell precursor ALL, the progression of preleukemia to ALL is believed to be due to aberrant immune responses to infection.

Longer exclusive breastfeeding durations can prevent immune system dysregulation in infants.

The transmission of antibodies and the anti-inflammatory properties of breastmilk can provide the infant with a robust immune system and help establish a healthy gut microbiome in the infant, which helps in the maturation of the immune system.

Conclusions

Overall, the findings supported the importance of breastfeeding and ensuring longer durations of an exclusively breastmilk diet in reducing the risk of childhood cancers such as ALL.

The study reported a significantly lower risk of B-cell precursor ALL in infants fed exclusively on breastmilk for more than three months as compared to infants who were breastfed for less than three months.