Breastfeeding Duration and the Risk of All-Cause and Breast Cancer Mortality Among Parous Women From the Mexican Teachers’ Cohort

Abstract

Abstract 79 Purpose Women who have breastfed have a lower risk of breast and ovarian cancer and other chronic diseases. Currently, breast cancer has become the leading cause of death from cancer in Mexican women. In Mexico, exclusive breastfeeding rates have declined one third in the last decade, and only 35% of women breastfed at least 1 year, which provides a unique scenario in which to analyze breastfeeding and mortality. The aim of the current study was to estimate the impact of lifetime breastfeeding duration on the risk of all-cause and breast cancer mortality in Mexican women. Methods We analyzed parous women who were enrolled in a Mexican Teachers’ Cohort since 2006 and observed over 10 years. Months of breastfeeding per pregnancy were self-reported at baseline. We categorized participants according to the accumulated duration of any mode of breastfeeding (never, < 6 months, 6 to 11 months, 12 to 23 months, and ≥ 24 months). Deaths were identified using the employer’s database and next of kin reports, and the date and cause of death were obtained from national mortality databases. We used Cox proportional hazards regression models adjusted for baseline age, parity (one, two, three, and four or more children), age at first birth (< 20, 20 to 24, 25 to 29, and ≥ 30 years), BMI at age 18 years (≤ 25 or > 25), socioeconomic level (tertiles), and smoking (current, past, and never) to estimate hazard ratios (HRs). Results Mean age at baseline was 43 ± 7 years. Over 767,600 person-years of follow-up, 952 all-cause deaths and 92 breast cancer deaths occurred among 92,794 parous women. Mean age at death was 57 ± 7 years. The incidence rate per 1,000 person-years of all-cause mortality was 1.8 for women who did not breastfeed, 1.18 (< 6 months), 1.21 (6 to 11 months), 1.01 (12 to 23 months), and 1.26 (≥ 24 months). HRs for all-cause mortality among parous women with lifetime breastfeeding of < 6 months was 0.79 (95% CI, 0.63 to 0.97), 0.85 (95% CI, 0.70 to 1.05) for 6 to 11 months, 0.78 (95% CI, 0.64 to 0.94) for 12-23 months, and 0.88 (95% CI, 0.69 to 1.10) for > 24 months compared with parous women who never breastfed. No dose-response relationship was found when comparing HRs of the different categories of breastfeeding. HR for breast cancer mortality for women who ever breastfed compared with parous women who never breastfed was 0.75 (95% CI, 0.45 to 1.33). Conclusion Breastfeeding among parous Mexican women was associated with lower all-cause mortality. Breastfeeding could potentially reduce premature deaths in women. AUTHORS' DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST No COIs from the authors.