Cumulative breastfeeding duration and incidence of diabetes in the multiethnic cohort study

Objectives To examine the association between breastfeeding duration and incidence of type 2 diabetes (T2D) across five racial and ethnic groups. Background Breastfeeding is a potent protective factor for many adverse perinatal outcomes and subsequent chronic disease conditions. Compared to non-breastfeeding parous women, multinational meta-analysis revealed that women who breastfed, especially for a duration extending beyond 12 months, experienced a significant T2D risk reduction later in life. This study will examine the relationship between breastfeeding and T2D in women from five racial and ethnic groups with a range of risks. Methods All multiethnic cohort (MEC) women who completed the 2003-2008 follow-up questionnaire when breastfeeding was assessed. Incident T2D was assessed using self-reported data and administrative data sources. Cox proportional hazards regression of incident T2D with age as the time metric stratified by race and ethnicity estimated its association with breastfeeding adjusted for relevant covariates. Results After exclusion of prevalent T2D cases, 5122 incident cases were detected. Of these, 53% of women without incident T2D ever breastfed in comparison to 51.8% of those with incident T2D. In women with any number of children, cumulative breastfeeding duration of ≥24 months resulted in an adjusted hazard ratio (HR) of 0.87 [0.78, 0.96], P-value <.01. In models examining any breastfeeding stratified by race and ethnic group, a lower risk was observed only in White women (adjusted HR of 0.87 [0.77,0.98], P-value < .02) while for cumulative duration of ≥24 months a lower risk was observed only in Native Hawaiian women (adjusted HR of 0.65 [0.45,0.93], P-value < .02). Conclusions Risk of T2D was reduced with cumulative duration of breastfeeding ≥24 months, especially in Native Hawaiian women. Extended breastfeeding should be encouraged as a preventative strategy for T2D prevention, especially in Native Hawaiian women who have a high risk for T2D.