By Traci Pantuso, MD
Adjunct Faculty, Research Investigator, Bastyr University, Seattle
SUMMARY POINTS
- Both the World Health Organization (WHO) and the United Nations Children’s Fund (UNICEF) recommend that all infants initiate breastfeeding within the first hour of life and exclusively breastfeed for six months.
- Numerous long-term benefits of breastfeeding include lower risk of asthma, obesity, and sudden infant death syndrome and higher performance on intelligence tests and cognitive development.
- By the year 2025, the WHO and UNICEF are working to have at least half of all the mothers worldwide exclusively breastfeeding their infants in the first six months of life.
SYNOPSIS: Any breastfeeding, including within the first days of life, is associated with significantly lower systolic blood pressure at 3 years of age in participants in the Canadian Healthy Infant Longitudinal Development Cohort Study.
SOURCE: Miliku K, Moraes TJ, Becker AB, et al. Breastfeeding in the first days of life is associated with lower blood pressure at 3 years of age. J Am Heart Assoc 2021;10:e019067.
Breastfeeding may have beneficial effects on cardiovascular development by providing bioactive factors and critical nutrients.1 There is conflicting evidence on the association of breastfeeding and blood pressure in children demonstrated by two previously published meta-analyses.2,3
The authors of this study speculated that the inconsistency between these two studies may be related to the use of different breastfeeding definitions. To better understand the effects of breastfeeding on blood pressure, the authors investigated different durations and timing of breastfeeding in children enrolled in the Canadian Healthy Infant Longitudinal Development (CHILD) Cohort Study and measured blood pressure in these same children at 3 years of age
The CHILD Cohort Study is a prospective longitudinal birth cohort study recruited from the general population at four sites in Canada. Women with singleton pregnancies from Vancouver, Edmonton, Manitoba, and Toronto were enrolled between 2008 and 2012 and remained eligible if they delivered a healthy infant > 34 weeks gestation (n = 3,455). At 3 years of age, blood pressure was measured during a clinical assessment. In the present study, 2,382 children had information on breastfeeding and blood pressure measurements available. At the ages of 3, 6, 12, 18, and 24 months, data were collected from questionnaires completed by caregivers.
Race/ethnicity, maternal age, education level (completion of postsecondary degree), smoking during pregnancy (any or none), and stress during pregnancy (never/almost never, sometimes, and often) were self-reported at enrollment during the second or third trimester of pregnancy. Delivery mode and preeclampsia diagnosis were extracted from medical records. Maternal body mass index (BMI) was calculated from measured height and self-reported prepregnancy weight, which were validated against health records in a subset. Weight at birth, gestational age, infant sex, and length of hospital stay also were extracted from medical records. The height and weight of the children were measured at 3 years of age, and BMI and Z scores were calculated using the World Health Organization (WHO) reference standard.
Questionnaires also were completed by caregivers assessing child screen time and servings of sugar-sweetened beverages. For the statistical analysis, chi-square tests were used to evaluate categorical variables. Continuous variables were assessed with analysis of variance, and Kruskal-Wallis tests were used for non-normally distributed variables. Multivariable linear regression models were used to assess the association of breastfeeding and child blood pressure. The authors controlled for confounding variables.
The authors categorized breastfeeding into the first days of life or none, early limited breastfeeding (breastfeeding limited to the hospital stay), or sustained (breastfeeding initiated and continued after hospital discharge). The authors further categorized the duration of breastfeeding into less than three months, three to less than six months, six to less than 12 months, and at least 12 months. The authors also defined breastfeeding exclusivity at three months as follows:
- exclusive (breast milk only, without any formula, other milk, solid foods, or fluids since birth);
- partial (breast milk plus any formula, other milk, solid foods, or fluids); and
- none (no breast milk).
In all, 2,382 children attended their three-year follow-up assessment out of the 3,455 enrolled children. To eliminate outliers, 44 children were excluded from the analyses because their blood pressures were four standard deviations away from the mean. The Z scores and percentiles were calculated for individual systolic and diastolic blood pressure values using normative values from “The Fourth Report on the Diagnosis, Evaluation, and Treatment of High Blood Pressure in Children and Adolescents” from the National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents. Of the 2,382 children, 2,333 (98%) had been breastfed, with 98 children receiving only breast milk in the first days of life. Meanwhile, 62% were breastfed exclusively for the first three months, and 78% were breastfed for six months or more.
The mean standard deviation of systolic blood pressure of the children at 3 years of age was 99 mmHg (standard deviation of ±9; Z score = 0.72; 70th percentile), and the mean diastolic blood pressure was 57 mmHg (standard deviation of ±7; Z score = 0.86; 77the percentile). When the authors compared children who were breastfed with children who never were breastfed, the breastfed children had significantly lower systolic blood pressure (-3.65 mmHg [95% confidence interval (CI), -6.23 to -1.07]), and systolic blood pressure Z scores (-0.31 [95% CI, -0.56 to -0.06]).
The association of lower systolic blood pressure and breastfeeding was independent of potential confounding variables. Lower diastolic blood pressure also was associated with children who had been breastfed compared to those who had not been breastfed, but this association was not significant. Interestingly, no dose response of breastfeeding duration or exclusivity at three months was found. The authors found that even early, limited breastfeeding was significantly associated with lower systolic and diastolic blood pressure at age 3 years (fully adjusted BMI model: -4.24 mmHg [95% CI, -7.45 to -1.04] and -2.62 mmHg [95% CI, -4.87 to -0.37], respectively) compared to never breastfeeding.
The mothers who never breastfed were younger, had an increased likelihood of smoking and were less likely to have a postsecondary degree compared with those who breastfed for any length of time. The 2,382 children who attended the 3-year follow-up assessment were more likely to be exclusively breastfed for at least three months than the children who did not attend (n = 883).
COMMENTARY
The strengths of this study are its large prospective trial design with participants from a general population. The incorporation of breastfeeding data from hospital records, which is rare in this area of research, also helped. Blood pressure also was assessed in early childhood before the onset of many traditional cardiovascular disease risk factors, such as smoking.
Limitations of this study include the lack of collection of two repeated blood pressure measurements, as recommended by the 2017 Hypertension Clinical Practice Guidelines.4 Additionally, 26% of participants were missing blood pressure data; children without blood pressure data were less likely to be breastfed exclusively, and their mothers were less educated and more likely to smoke. The overall population of the participants was of a higher socioeconomic status, with high breastfeeding initiation rates, which may limit the generalizability of the results of this study. There was a small number of children who were in the never-breastfed group (n = 49), which limits the statistical power in comparisons with this group.
The results of this study add to the larger body of research supporting the health benefits of breastfeeding for both mom and child.5-7 Elevated blood pressure in childhood and adolescence is correlated with hypertension and an increased risk of cardiovascular disease in adulthood.8,9 The maternal health benefits include decreased risk of breast and ovarian cancers and of type 2 diabetes.7
If the WHO and United Nations Children’s Fund guidelines for breastfeeding had 100% uptake globally, an estimated 98,243 fewer women would die of breast and ovarian cancers and type 2 diabetes yearly, 595,375 fewer children would die from pneumonia and diarrhea each year, and there would be 975,000 fewer yearly cases of childhood obesity.7 Also, inadequate breastfeeding is estimated to cost $340 billion globally in avoidable healthcare costs and lost earnings.7
In spite of the clear benefits of exclusive breastfeeding for the first six months, only an estimated 40% of children worldwide are breastfed.7 In the United States, only 24% of infants are exclusively breastfed for six months.7 There are numerous structural and personal barriers that affect women’s ability to breastfeed, however, and the research literature is growing in this area.10
The bottom line is that recommending and supporting breastfeeding in any capacity (in addition to formula, if needed) should be performed with patients. If patients are having difficulty with breastfeeding, referral to a lactation consultant may be helpful to address issues breastfeeding women and children are having.
REFERENCES
- van Rossem L, Wijga AH, de Jongste JC, et al. Blood pressure in 12-year-old children is associated with fatty acid composition of human milk: The prevention and incidence of asthma and mite allergy birth cohort. Hypertension 2012;60:1055-1060.
- Martin RM, Gunnell D, Smith GD. Breastfeeding in infancy and blood pressure in later life: Systematic review and meta-analysis. Am J Epidemiol 2015;161:15-26.
- Owen CG, Whincup PH, Gilg JA, Cook DG. Effect of breast feeding in infancy on blood pressure in later life: Systematic review and meta-anaysis. BMJ 2003;327:1189-1195.
- National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents. The fourth report on the diagnosis, evaluation, and treatment of high blood pressure in children and adolescents. Pediatrics 2004;114(2 Suppl 4th Report):555-576.
- United Nations Children’s Fund. From the First Hour of Life: Making the Case for Improved Infant and Young Child Feeding Everywhere. New York; 2016.
- Westerfield KL, Koenig K, Oh R. Breastfeeding: Common questions and answers. Am Fam Physician 2018;98:368-373.
- Walters DD, Phan LTH, Mathisen R. The cost of not breastfeeding: Global results from a new tool. Health Policy Plan 2019;34:407-417.
- Chen X, Wang Y. Tracking of blood pressure from childhood to adulthood: A systematic review and meta-regression analysis. Circulation 2008;117:3171-3180.
- McCarron P, Smith GD, Okasha M, McEwen J. Blood pressure in young adulthood and mortality from cardiovascular disease. Lancet 2000;355:1430-1431.
- Sayres S, Visentin L. Breastfeeding: Uncovering barriers and offering solutions. Curr Opin Pediatr 2018;30:591-596.
