History of Breastfeeding in Relation to Circulating Inflammatory and Metabolic Biomarkers.

Background: Breastfeeding history has been associated with reduced risk of chronic diseases, although the underlying biological link is unclear.

Methods: The study included 16,165 parous women in the Nurses' Health Studies who reported lactation history and biomarkers measured using plasma samples collected at midlife. We calculated multivariable-adjusted geometric means of 10 inflammatory biomarkers [high-sensitivity C-reactive protein, IL6, IL8, IL10, insulin-like growth factor 1 (IGF1), soluble TNFα receptor 2, B cell-activating factor, C-X-C motif chemokine ligand 13, soluble IL2 receptor α, and soluble IL6 receptor-α] and eight metabolic biomarkers (triglyceride, total cholesterol, high- and low-density lipoprotein, leptin, soluble leptin receptor, adiponectin, and retinol-binding protein 4) by the self-reported history of breastfeeding prior to blood collection. The FDR was used for multiple testing corrections.

Results: The average age at blood collection was 52.6 years. Ever breastfeeding was associated with higher IGF1 (149.22 vs. 143.76 ng/mL; P value = 0.0002/FDR = 0.004) compared with never breastfeeding. Longer breastfeeding duration was associated with lower IL10 (P-trend = 0.001/FDR = 0.01) and higher IGF1 (P-trend = 0.0005/FDR = 0.01). No significant associations were observed for other biomarkers. Longer breastfeeding duration was associated with higher IGF1 among premenopausal women but not among postmenopausal women (P-interaction = 0.02). Longer breastfeeding duration was associated with lower soluble leptin receptor levels among those with body mass index ≥25 kg/m2 (P-trend = 0.01/FDR = 0.09) but not among those with body mass index <25 kg/m2 (P-interaction = 0.0002).

Conclusions: Ever breastfeeding and longer breastfeeding duration were associated with higher IGF1 levels measured in midlife.

Impact: Our results support the potential long-term systemic impact of breastfeeding on circulating IGF1 levels, which may influence future chronic disease risk.