Exclusive breastfeeding for longer than three months has been linked to a smaller risk of childhood leukaemia, a recent population-based cohort study showing a reduced risk of B-cell precursor acute lymphoblastic leukaemia (BCP-ALL), according to the Danish researchers.
Compared with an exclusive breastfeeding duration of less than three months, exclusive breastfeeding for three months or longer was associated with a decreased risk of haematologic cancers (adjusted HR 0.66, 95% CI 0.46-0.95), which was largely attributable to a decreased risk of BCP-ALL (aHR 0.62, 95% CI 0.39-0.99), reported Signe Holst Søegaard, PhD, of the Danish Cancer Institute and Danish Cancer Society in Copenhagen, and colleagues.
There was no association between exclusive breastfeeding duration and risk of central nervous system tumours (aHR 0.96, 95% CI 0.51-1.88) or solid tumours (aHR 0.87, 95% CI 0.55-1.41), they noted in JAMA Network Open.
“Our analyses thereby corroborate previous observations from case-control studies suggesting that breastfeeding is associated with risk of childhood ALL,” they wrote.
“Notably, our results for BCP-ALL align with the approximately 30% reduced ALL risk in children breastfed exclusively for at least four months versus never breastfed in recent pooled analyses of international case-control studies, including more than 10 000 children with ALL.”
The authors also suggested that the finding of a reduced risk of BCP-ALL "is consistent with emerging investigations implicating early gut microbiome maturation in childhood BCP-ALL pathogenesis”, reports Medpage Today.
In a commentary accompanying the study, Helen Bailey, PhD, of Curtin University in Perth, Australia, noted that this was the first population-based cohort study to report that prolonged exclusive breastfeeding may be associated with decreased risk of childhood ALL.
However, she also pointed out that while BCP-ALL is one of the most common childhood cancers, it is still rare, and the reduced relative risk of developing BCP-ALL seen in this study translates into a minimum change in the level of absolute risk.
“Thus, it is unlikely that these findings alone would influence a woman’s breastfeeding practice,” Bailey wrote.
Yet prolonged breastfeeding has also been shown to have many short- and long-term benefits for infants in all economic settings, she added, and the findings add to the existing evidence about the critical importance of exclusive breastfeeding.
Methodology
For this study, Søegaard and colleagues used administrative data on exclusive breastfeeding duration from the Danish National Child Health Register and included 309 473 children (51.3% male) born in Denmark from January 2005 to December 2018. These children were followed from one year until childhood cancer diagnosis, loss to follow-up oremigration, death, age 15 years, or 31 December 2020.
During follow-up, 332 children (0.1%) were diagnosed with cancer at ages one to 14 years (mean age at diagnosis 4.24 years, 58.4% male).
Of these kids, 37.3% were diagnosed with haematologic cancers, with 65.3% being ALL – almost all of which (91.4%) were BCP-ALL. Seven children were diagnosed with acute myeloid leukaemia (AML), and fewer than five were diagnosed with Hodgkin lymphoma.
The other children had central nervous system tumours (13.3%), solid tumours (24.1%), and other unspecified malignant neoplasms (25.3%).
In the full study cohort, 33.6% of children were exclusively breastfed for less than three months. Among those diagnosed with any cancer, the proportion of those breastfed for less than three months was 38.3%, and among those diagnosed with ALL, it was 42%.
The numbers of children diagnosed with AML or Hodgkin lymphoma prevented the authors from estimating any association of exclusive breastfeeding with these cancers.
Study details
Exclusive breastfeeding duration and risk of childhood cancers
Signe Holst Søegaard, Mie Mølgaard Andersen, Klaus Rostgaard, et al.
Published in JAMA Network Open on 26 March 2024
Abstract
Importance
Breastfeeding has been suggested to protect against childhood cancers, particularly acute lymphoblastic leukaemia (ALL). However, the evidence stems from case-control studies alone.
Objective
To investigate whether longer duration of exclusive breastfeeding is associated with decreased risk of childhood ALL and other childhood cancers.
Design, Setting, and Participants
This population-based cohort study used administrative data on exclusive breastfeeding duration from the Danish National Child Health Register. All children born in Denmark between January 2005 and December 2018 with available information on duration of exclusive breastfeeding were included. Children were followed up from age 1 year until childhood cancer diagnosis, loss to follow-up or emigration, death, age 15 years, or December 31, 2020. Data were analysed from March to October 2023.
Main Outcomes and Measures
Associations between duration of exclusive breastfeeding and risk of childhood cancer overall and by subtypes were estimated as adjusted hazard ratios (AHRs) with 95% CIs using stratified Cox proportional hazards regression models.
Results
A total of 309 473 children were included (51.3% boys). During 1 679 635 person-years of follow-up, 332 children (0.1%) were diagnosed with cancer at ages 1 to 14 years (mean [SD] age at diagnosis, 4.24 [2.67] years; 194 boys [58.4%]). Of these, 124 (37.3%) were diagnosed with hematologic cancers (81 [65.3%] were ALL, 74 [91.4%] of which were B-cell precursor [BCP] ALL), 44 (13.3%) with central nervous system tumours, 80 (24.1%) with solid tumours, and 84 (25.3%) with other and unspecified malignant neoplasms. Compared with exclusive breastfeeding duration of less than 3 months, exclusive breastfeeding for 3 months or longer was associated with a decreased risk of hematologic cancers (AHR, 0.66; 95% CI, 0.46-0.95), which was largely attributable to decreased risk of BCP-ALL (AHR, 0.62; 95% CI, 0.39-0.99), but not with risk of central nervous system tumours (AHR, 0.96; 95% CI, 0.51-1.88) or solid tumours (AHR, 0.87; 95% CI, 0.55-1.41).
Conclusions and Relevance
In this cohort study, longer duration of exclusive breastfeeding was associated with reduced risk of childhood BCP-ALL, corroborating results of previous case-control investigations in this field. To inform future pre-emptive interventions, continued research should focus on the potential biologic mechanisms underlying the observed association.
Medpage Today article – Breastfeeding Tied to Reduced Childhood Leukaemia Risk (Open access)
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