"We saw 36% to 57% relative reductions in the 2-year [diabetes mellitus] incidence with higher intensity of lactation at 6 to 9 weeks postpartum as well as for longer periods (>2 months through >10 months), independent of obesity, gestational glucose tolerance, and perinatal outcomes that can delay lactogenesis and thereby shorten lactation duration," Erica P. Gunderson, PhD, MPH, RD, an epidemiologist and senior research assistant at Kaiser Permanente, Oakland, California, and colleagues write.
The results of the prospective cohort study were published online November 23 in the Annals of Internal Medicine.
In multivariable regression models, after adjusting for age and covariates (including maternal and perinatal risk factors, newborn outcomes, and lifestyle behaviors), higher lactation intensity was associated with lower rates of incident type 2 diabetes (all P trends < .025). And compared with a short lactation duration of 0 to 2 months, longer lactation duration (>2 to 5 months, >5 to 10 months, and >10 months) was also independently associated with lower rates of incident type 2 diabetes (all P trends < .01).
Although the authors acknowledge the inability to evaluate the associations beyond 2 years of follow-up as one of the major limitations of this study, they emphasize that, by design, SWIFT minimized the reverse causality and residual confounding that reduce the validity of earlier studies. "[T]o date, SWIFT was the largest and most ethnically diverse prospective cohort of women with GDM to conduct glucose tolerance testing annually from the early postpartum period, and is the only study that prospectively quantified lactation intensity and duration and controlled for several perinatal and newborn potential confounders," they write.
On the basis of the results of this study, the researchers emphasize the need to refocus strategies to reduce the risk for incident type 2 diabetes in postpartum women.
"Modification of lactation behaviors to increase intensity and duration should be considered a high priority for pregnant and postpartum women with GDM because of their lasting metabolic benefits. Greater allocation of health care resources to promote and support exclusive and extended breastfeeding may benefit high-risk women by reducing their risk for midlife progression to [diabetes mellitus]," the authors conclude.
This study was funded by the National Institute of Child Health and Human Development. Coauthors also received grants from the Kaiser Permanente Community Benefit Program, the WK Kellogg Foundation, the National Institutes of Health National Center for Research Resources, and the American Diabetes Association and financial support from Takeda, Merck, sanofi-aventis, Lilly, Genentech, Valeant, and Pfizer.
Ann Intern Med. Published online November 23, 2015. Abstract
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