Breastfeeding Is Inversely Associated with Allostatic Load in Postpartum Women: Cross-Sectional Data from Nationally...

The postpartum period is a critical transition period when exposures to protective factors such as breastfeeding can have long-lasting health impact. Studies have suggested downregulating effects of breastfeeding on stress biomarkers such as cortisol but have not explored the way breastfeeding interacts with allostatic load, a multisystem indicator of chronic stress.

We aimed to examine the association between breastfeeding and maternal allostatic load among women within 2 y postpartum using nationally representative data.

A cross-sectional analysis of 10 waves of data from the NHANES (1999-2018) was conducted in a sample of 1302 women aged ≥18 y who provided information on breastfeeding through the reproductive health questionnaire. Clinical and empirical allostatic load scores (range: 0-10; higher numbers associated with increased risk) were derived for each participant based on 10 biomarkers reflecting metabolic, cardiovascular, and immune health. Multiple linear regression tested associations between breastfeeding and allostatic load, adjusting for maternal age, race and ethnicity, education, poverty level, and survey wave.

Breastfeeding had a significant inverse association with allostatic load in unadjusted and adjusted models. Controlling for age, race and ethnicity, education, poverty level, and survey wave, breastfeeding women had a 0.36-point lower clinical allostatic load score than nonbreastfeeding women (β = -0.36, SE = 0.11; 95% CI: -0.59, -0.14; P = 0.002) and a 0.44-point lower empirical allostatic load score (β = -0.44, SE = 0.15; 95% CI: -0.74, -0.14; P = 0.005).

Our study suggests that breastfeeding is protective of maternal stress and provides a more comprehensive picture of breastfeeding's influence on multiple body systems, exemplifying physiological benefits beyond effects on single biomarkers. However, limitations of cross-sectional data and non-classification of breastfeeding duration, mode, and intensity should be considered when interpreting these findings, and further research to address the role of breastfeeding and allostatic load is needed.