Duration and intensity of being breastfed and educational attainment, income and labour force participation: a prospective cohort and sibling study from Denmark

Abstract

Objective

Breastfeeding improves cognitive ability in childhood, but the long-term impact on socioeconomic outcomes remains unknown. We examined associations between durations of predominant and any breastfeeding and educational attainment, income, and labor force participation in adulthood, and whether these varied by maternal education.

Study design

Prospective cohort study.

Methods

We followed 84,255 individuals born 1959–1967 with prospectively collected information on breastfeeding duration and intensity from the Copenhagen Infant Health Nurse Records. Socioeconomic outcome information came from national registers (1980–2020). Linear and Poisson regression were used, and models were adjusted for prenatal and postnatal variables across three levels of maternal education.

Results

Durations of being breastfed exhibited associations with all outcomes, with most being more pronounced among mothers with low education. Compared with infants breastfed <1 month, those breastfed ≥5 months had 0.68 (95% confidence interval: 0.60–0.76), 0.55 (0.45–0.65), and 0.65 (0.46–0.84) additional years of education for infants born to mothers with low, medium, or high education, respectively. Moreover, infants breastfed ≥5 months had 4047, 3713, and 1902 US$ higher annual incomes and were 23% less likely to be outside the labor force at age 50 years. These associations were stronger with longer breastfeeding durations and for predominant than any breastfeeding.

Conclusions

Prolonged and higher breastfeeding intensity consistently exhibited dose-dependent associations with improved socioeconomic indicators in adulthood. Notably, these relationships were more pronounced among individuals whose mothers had lower educational attainment. Consequently, our findings suggest that breastfeeding may have a lasting positive influence on socioeconomic outcomes, particularly for the most disadvantaged infants.