First large study of CVD in mothers
Emerging individual studies suggest that mothers who breastfeed may have a lower risk for CVD in later life, but studies have been inconsistent, and it is not clear if longer breastfeeding would strengthen this benefit, the authors note.
To examine this, they pooled data from the following eight studies (with study acronym, country, and baseline enrolment dates in brackets): 45&Up (Australia, 2006-2009), China Kadoorie Biobank (CKB, China, 2004-2008), European Prospective Investigation into Cancer and Nutrition (EPIC, multinational, 1992-2000), Gallagher et al. (China, 1989-1991), Nord-Trøndelag Health Survey 2 (HUNT2, Norway, 1995-1997), Japan Public Health Center-based Prospective Study (JPHC, Japan, 1990-1994), Nurses’ Health Study (NHS, U.S., 1986), and the Woman’s Health Initiative (WHI, U.S., 1993-1998).
On average, the women were 51.3 years old (range, 40-65 years) when they enrolled in the study, and they were followed for a median of 10.3 years (range, 7.9-20.9 years, in the individual studies).
On average, they had their first child at age 25 and had two to three children (mean, 2.3); 82% had breastfed at some point (ranging from 58% of women in the two U.S. studies to 97% in CKB and HUNT2).
The women had breastfed for a mean of 7.4 to 18.9 months during their lifetimes (except women in the CKB study, who had breastfed for a median of 24 months).
Among the 1,192,700 women, there were 54,226 incident CVD events, 26,913 incident CHD events, 30,843 incident strokes, and 10,766 deaths from CVD during follow-up.
The researchers acknowledge that study limitations include the fact that there could have been publication bias, since fewer than 10 studies were available for pooling. There was significant between-study heterogeneity for CVD, CHD, and stroke outcomes.
Participant-level data were also lacking, and breastfeeding was self-reported. There may have been unaccounted residual confounding, and the benefits of lifetime breastfeeding that is longer than 2 years are not clear, because few women in this population breastfed that long.
The research was funded by the Austrian Science Fund. The researchers and Dr. Mehran and Dr. O’Donoghue have no relevant financial disclosures.
A version of this article first appeared on Medscape.com.