Longer duration of breastfeeding was associated with a lower risk of diabetes among mothers later in life, according to a 30-year observational study.
Among more than 1,200 young white and black women (mean age 24.2), increasing lactation duration was associated with a graded 25% to 47% relative reduction in the incidence of diabetes, even after accounting for factors such as prepregnancy biochemical measures, clinical and demographic risk factors, gestational diabetes (GD), and lifestyle behaviors, reported Erica P. Gunderson, PhD, MPH, of Kaiser Permanente in Northern California in Oakland, and colleagues, in JAMA Internal Medicine.
Gunderson’s group found a strong inverse association between diabetes incidence and lactation duration compared with 0 days:
- >0 to 6 months: relative hazards 0.75 (95% CI0.51-1.09, P=01)
- >6 months to <12 months: RH 0.52 (95% CI 0.31-0.87, P=01)
- ≥12 months: RH 0.53 (95% CI 0.29-0.98, P=01)
“Our findings in young black and white women are consistent with studies in high-risk women with GD that re-screened women systematically for diabetes after pregnancy,” the authors stated. “This strong graded, protective association is strikingly similar in magnitude to our 30-year follow-up risk reduction in healthy CARDIA women.”
They explained that lactation is a natural biological process, which had the potential to provide long-term benefits to maternal health, “but has been underappreciated as a potential key strategy for early primary prevention of metabolic diseases in women across the childbearing years and beyond.”
Gunderson’s group collected data on 1,238 women from the Coronary Artery Risk Development in Young Adults (CARDIA) study of young black (n=615) and white women, ages 18-30 year,s without diabetes at baseline (1985-1986). The community-based sampling occurred in four geographic areas in the country: Birmingham, Alabama; Chicago; Minneapolis; and Oakland.
All women had one or more live births after baseline, reported lactation duration, and were screened for diabetes up to seven times during 30 years after baseline (1986-2016).
Gunderson’s group reported 182 incident diabetes cases during 27,598 person-years for an overall incidence rate of 6.6 cases per 1,000 person-years (95% CI 5.6-7.6). Of this group, there were 132 cases (73.0%) in 13,369 person-years for black women and 50 cases in 14,229 person-years for white women.
Diabetes incidence per 1,000 person-years was higher in black women (9.9. 95% CI 8.2-11.6, P<0.001) than white women (3.5, 95% CI 2.5-4.5, P<0.001) and the rate was 18.0 (95% CI 13.3-22.8, P<0.001) for women with gestational diabetes and 5.1 (95% CI 4.2-6.0, P<0.001) for women without.
There was no evidence of effect modification by race, gestational diabetes, or parity, the researchers added.
They explained that there are several mechanisms that might explain the link between lactation duration and lower risk of diabetes, including that lactating women have lower circulating glucose in both fasting and post-absorptive states, as well as lower insulin secretion, despite increased glucose production rates.
The researchers concluded that their findings may have implications for social policies. For example, the findings support extending paid maternity leave to achieve a longer duration of breastfeeding, as well as an increased allocation of healthcare resources to increase breastfeeding rates in order to help prevent chronic disease in women, and prevent obesity-related diseases.
Study imitations included self-report of pregnancy complications and the inability to explain the reasons behind the association.
The study was supported by the National Institute of Diabetes, Digestive, and Kidney Disease. CARDIA is supported by multiple institutions including the National Heart, Lung, and Blood Institute.
Gunderson disclosed funding from Janssen Pharmaceuticals. One co-author disclosed relevant relationships with Takeda, Merck, Sanofi-Aventis, Lilly, Genentech, Valeant, and Pfizer.