Lactation and maternal risk of diabetes: Evidence from the Mexican Teachers' Cohort

Abstract

One postpartum behaviour that may be protective against diabetes is lactation due to its potential role in resetting maternal metabolism after pregnancy. However, the role of lactation in maternal risk of diabetes has not been investigated in Latin American populations, where rates of breastfeeding are suboptimal and diabetes incidence is increasing. Therefore, our aim was to estimate the association between mean duration of lactation per child and maternal incidence of diabetes. We followed 66,573 women from the Mexican Teachers' Cohort free of diabetes at baseline. Incident diabetes was ascertained through triennial questionnaires and lactation history was asked in baseline questionnaire. We used Cox proportional hazards regression models to estimate the hazard ratio (HR) for diabetes by mean duration of lactation per child. We examined the dose–response association between lactation per child and diabetes with restricted cubic splines. We found that 3,168 incident cases of diabetes were diagnosed during 157,510 person years of follow‐up. In comparison with women who did not breastfed, women with a mean lactation per child of 3 to <6 months and 6 to <12 months had HRs of 0.81 (95% CI [0.65, 0.99]) and 0.73 (95% CI [0.59, 0.91]), respectively (p for quadratic term 0.004). There was no further decline in risk of diabetes after ≥12 months of lactation per child. The dose–response association between lactation and diabetes was linear up to 9 months of lactation. Our findings suggest that lactation is associated with reduced incidence of diabetes, indicating considerable potential for diabetes prevention on a population level.

Association of lactation with maternal risk of type 2 diabetes: A systematic review and meta‐analysis of observational studies

“…Ten studies were restricted to patients with a diagnosis of GD, whilst the remaining 12 included a mix of patients with and without GD, of which six stated the proportion of women with GD. Duration of lactation was classified differently across studies as (a) total lifetime duration of lactation, 13,24,26,32,34 (b) average duration of lactation per child, 24,26,28,33 (c) total duration for a single pregnancy in studies that followed up women after a specific pregnancy, 10,12,21,22,25,27,[29][30][31]35 and (d) lactation at hospital discharge. 14,23 Follow-up varied from 4 to 12 weeks for studies that evaluated the short-term association between lactation and type 2 diabetes after birth, and up to 25 years.…”

“…[10][11][12]22 Studies with a longer follow-up showed a protective association between lactation and the RR of type 2 diabetes, with a stronger association in women with GD than in those without GD. 13,[31][32][33] The extent of the benefit seemed to increase in parallel with duration of lactation and to be independent of well-established risk factors for type 2 diabetes, such as obesity, ethnicity, diet, exercise, weight gain and antecedent metabolic risk profiles. 24,28,34 Meta-analysis of studies that compared ever with never lactation 14,[21][22][23][24][25][26][27][28][29][30][31] suggested that lactation was associated with a 27% lower risk of type 2 diabetes (RR 0.73, 95% CI [0.65, 0.83]) (Figure 1).…”

“…All studies that reported adjusted risk estimates were included in the first meta-analysis, 14,[21][22][23][24][25][26][27][28][29][30][31] and those that reported effect sizes for intervals of duration of lactation were included in the second metaanalysis. 13,26,29,[31][32][33][34] Three studies contributed to both analyses. 26,29,31 Reported hazard ratios for type 2 diabetes with 95% confidence intervals (CIs), with adjustment for confounders, were extracted for cohort studies, when available.…”

“…The association between lactation and maternal risk of type 2 diabetes was explored in two complementary analyses: (a) ever versus never lactation and (b) according to duration of lactation. All studies that reported adjusted risk estimates were included in the first meta‐analysis, 14,21–31 and those that reported effect sizes for intervals of duration of lactation were included in the second meta‐analysis 13,26,29,31–34 . Three studies contributed to both analyses 26,29,31 …”

Breastfeeding practices in Mexico: Results from the National Demographic Dynamic Survey 2006–2018

“…Conversely, feeding infants with infant formula has a deleterious effect on their health (Anttila‐Hughes, Fernald, Gertler, Krause, & Wydick, 2018; Mameli et al, 2016). Breastfeeding has important health benefits for the mother who breastfeeds (Chowdhury et al, 2015; Mazariegos et al, 2019; Unar‐Munguia, Torres‐Mejia, Colchero, & Gonzalez de Cosio, 2017), and only a small percentage of women are unable to breastfeed (~5%) due to serious disease or adoption (Lawrence & Lawrence, 2005).…”