Breastfeeding for 6 months or more was associated with a slimmer waist in mothers years later, compared with shorter or no breastfeeding, new data show.
“Waist circumference…as a measure of central adiposity has been shown to be a superior proxy for assessing long-term risk of coronary artery disease mortality, hypertension, diabetes, dyslipidemia, and the metabolic syndrome, independent of BMI,” Gabrielle G. Snyder, MPH, University of Pittsburgh, Pennsylvania, and colleagues note.
Thus, “breastfeeding duration may be important to consider when studying long-term maternal cardiovascular and metabolic health,” they conclude in their article published online December 11 in the Journal of Women’s Health.
“We consistently detected that a threshold effect may exist,” they report, “for breastfeeding greater than 6 months.” The benefit remained after accounting for demographic, lifestyle, and socioeconomic factors.
Snyder and colleagues analyzed data from 676 women in the Pregnancy Outcomes and Community Health (POUCH) cohort who participated in the POUCHmoms study, 7 to 15 years after delivery. They matched moms with a similar likelihood to breastfeed, and then compared the moms who breastfed for > 6 months versus not at all or less than 6 months.
“This study extends conventional observational study methods,” they write, “to incorporate propensity score approaches that make it possible to…account for systematic differences in women who did and did not breastfeed.”
“Metabolically active visceral adipose tissue, a measure of abdominal obesity primarily distributed about the intra-abdominal organs, may increase substantially with a single pregnancy, independent of total body fat,” Snyder and colleagues write.
The World Health Organization recommends exclusive breastfeeding for 6 months for optimal infant health. In addition, breastfeeding consumes nearly 500 calories a day for moms.
Prior studies have reported that women who breastfed their babies had less central obesity years later than women who did not do this, but the studies did not account for different baseline characteristics of the women.
Therefore, Snyder and colleagues compared central obesity after about a decade in women in the POUCHmoms study who were seen in clinics in Michigan communities. Of the women in the cohort, 63% of the mothers were white, 31% were black, and 6% were Asian or Native American.
Prior to pregnancy, about half of the women (49%) had a body mass index (BMI) below 25 kg/m2 (normal weight) and the rest were overweight (21%) or obese (30%).
Overall, 38% of the mothers did not breastfeed their babies, while the others did so for > 0 to 3 months (22%), > 3 to 6 months (13%), or > 6 months (27%). In unadjusted analyses, women who breastfed for > 6 months were older and more likely to be white and have a higher education level, and less likely to be obese before pregnancy.
At a mean follow-up of 11 years, the mothers had a mean waist circumference of 94 cm if they had breastfed their child for up to 6 months, and 86 cm if they had breastfed longer.
Two types of propensity analyses showed that the mothers who reported breastfeeding their infants for more than 6 months had a mean waist circumferencethat was 3.6 cm smaller and 3.1 cm smaller than other mothers.
“We emphasize [waist circumference] as the outcome of interest,” the researchers write, “given that central adiposity is a better predictor of long-term cardiometabolic and cardiovascular disease risk than BMI alone.”
They acknowledge that study limitations include potential pre-pregnancy differences in diet and exercise, for example, that were not accounted for.
Snyder and colleagues call for more research to investigate the effect of breastfeeding in multiple pregnancies on lifetime risk of cardiovascular disease.
“Our results warrant further analyses of cumulative lifetime duration of breastfeeding,” they write, “to understand the magnitude of the relationship with maternal central adiposity over time.”