Breastfeeding Helps Lower the Risk for Maternal Heart Disease

Thanks to JC for sharing this picture

February is American Heart Month, a month to raise awareness about the frequency and impact of heart disease in U.S. society.  My colleagues over at the Association for Size Diversity and Health have a new blog post up about lowering your risk for heart disease, whatever your size.

But I have to add that there's one thing that women in particular can do to help lower their risk for heart disease, and that's ─ surprise! ─ breastfeeding, which brings it within the realm of this blog.

So, in honor of American Heart Month, let's discuss how long-term breastfeeding can help lower the risk for heart disease in the mother.

Research has traditionally focused on how breastfeeding may help lower the risk for various problems in a child as he grows up, but until fairly recently, there hadn't been a lot of data on whether it helped lower the risk for various heart risk factors for the mother.

Now, thanks to the Nurses Health Study, the Women's Health Initiative, CARDIA, and other studies, we know that breastfeeding is protective for the mothers as well, especially extended (or long-term) breastfeeding.

Below you will find the abstracts for a number of studies about how breastfeeding lowers the risk for hypertension, metabolic syndrome, diabetes, high fasting insulin levels, and high lipid levels.

Now, of course, there are some caveats to this research.  The overall effect for some factors is not huge, for example, and obviously many people who do breastfeed long-term go on to develop high blood pressure, diabetes, or heart disease.  There are multiple factors at work here, not just breastfeeding.

So it's important to remember that breastfeeding, even long-term breastfeeding, is not a guarantee against heart disease.  But even with these caveats, the findings are encouraging.  Here's something we can do that will really benefit both our babies and ourselves.

Notes on the Studies

Note that the length of breastfeeding time is an important variable which varies greatly among these studies.  Some studies looked at women who breastfed longer than 2 years, some at longer than 1 year, while others only looked at those who breastfed longer than 3 or 6 months.  There's likely a significant difference in risk between those who breastfed for only 3 months vs. those who breastfed for several years! So if anything, the effect might be even stronger.

Yet the 2010 diabetes study listed below only looked at women who breastfed longer than 1 month, and they still found an effect.  How much more of an effect might there be if they had followed women who had breastfed far more long-term?  THAT'S where this research needs to go in the future.

I'd also point out that this research is a pretty big condemnation of doctors in past generations discouraging women from breastfeeding.  That just goes to show that even with the best training, doctors can still be misguided, and the medical "standard of care" isn't always best for women or babies.  Doctors are human and sometimes they are misguided....and that can still be true today.

Even now, support for extended breastfeeding is still tepid among many physicians (like the one who told me there were no benefits to breastfeeding beyond about 6 weeks). There are far too many hospitals who only pay lip service to the idea of breastfeeding but whose policies actually impede it.  Much progress remains to be made in promoting breastfeeding, and that's even now, when we know how important it is.

Another vital point is that there is research not just on breastfeeding improving intermediate outcomes (risk factors for heart disease, like diabetes or hypertension), but also for it improving long-term outcomes (i.e., actual incidence of coronary heart disease, not just impact on risk factors).  As the press release for the 2009 study noted:

In their analysis of 89,326 parous women in the Nurses’ Health Study, Stuebe et al found that compared with women who had never lactated, women who had breastfed for 2 or more years had a 37 percent lower risk for CHD after adjusting for age, parity, stillbirth history, early-adult adiposity, parental history, and lifestyle factors. 

The authors note that this protective effect is characterized by a threshold effect at 2 years, as women had a hazard ratio (HR) of 0.87 for CHD if they had breastfed for more than 1 year versus no lactation, compared with 0.77 for 2 or more years. 

Considering the dose-response relationship they found, I wonder what the effect is for those of us who have breastfed far more than 2 years total?  Although my breastfeeding days are sadly over now, I spent about 10 years breastfeeding, cumulatively speaking.  Since I have significant risk factors for heart disease (what with the PCOS, insulin resistance, and a family history of CHD), I'm hoping this helps reduce some of that risk!

In the end, I think it's pretty darn conclusive that breastfeeding is not just good for babies, but for long-term maternal health as well.  We knew that was true for various cancers, but now we know it's true for heart health as well.

To lower the number of heart-related deaths, the CDC has joined together with several other organizations to promote the Million Hearts™ Initiative. They recommend the following ideas to help lower your risk for heart disease (and how refreshing is it that their recommendations are HAES-friendly!):

• Get up and get active by being physically active for at least 30 minutes on most days of the week.
• Know your ABCS:
• Ask your doctor if you should take an Aspirin every day.
• Find out if you have high Blood pressure or Cholesterol, and if you do, get effective treatment.
• If you Smoke, get help to quit.
• Make your calories count by eating a heart-healthy diet high in fresh fruits and vegetables and low in sodium and trans fat.
• Take control of your heart health by following your doctor's prescription instructions.

To this list, we can now add breastfeeding, especially long-term.  Breastfeeding is not a guarantee against heart problems, obviously, but it does seem to help, and any help to lower the risk for the number one cause of death is very welcome. 

*Please note, posting this research is not meant to make mothers who can't breastfeed feel bad.  Because PCOS can impact milk supply in some women, a number of my readers may well have experienced breastfeeding struggles, and I always want to be sensitive to that fact, even as I highlight the research supporting the benefits of breastfeeding.  I strongly encourage anyone who has struggled with breastfeeding issues to visit MOBI, Mothers Overcoming Breastfeeding Issues, and www.lowmilksupply.org, both of which are incredible resources for both information and support.

References

*Please note that a number of the following abstracts have links to free full texts of the studies.

Am J Obstet Gynecol. 2009 Feb;200(2):138.e1-8. Epub 2008 Dec 25. Duration of lactation and incidence of myocardial infarction in middle to late adulthood. Stuebe AM, et al.   PMID: 19110223

OBJECTIVE: We assessed the relation between duration of lactation and maternal incident myocardial infarction. STUDY DESIGN: This was a prospective cohort study of 89,326 parous women in the Nurses' Health Study. RESULTS: During 1,350,965 person-years of follow-up, 2540 cases of coronary heart disease were diagnosed. Compared with parous women who had never breastfed, women who had breastfed for a lifetime total of 2 years or longer had 37% lower risk of coronary heart disease (95% confidence interval, 23-49%; P for trend < .001), adjusting for age, parity, and stillbirth history. With additional adjustment for early-adult adiposity, parental history, and lifestyle factors, women who had breastfed for a lifetime total of 2 years or longer had a 23% lower risk of coronary heart disease (95% confidence interval, 6-38%; P for trend = .02) than women who had never breastfed.
CONCLUSION: In a large, prospective cohort, long duration of lactation was associated with a reduced risk of coronary heart disease.

Obstet Gynecol. 2009 May;113(5):974-82. Duration of lactation and risk factors for maternal cardiovascular disease. Schwarz EB, et al.   PMID: 19384111

OBJECTIVE: To examine dose-response relationships between the cumulative number of months women lactated and postmenopausal risk factors for cardiovascular disease.
METHODS: We examined data from 139,681 postmenopausal women (median age 63 years) who reported at least one live birth on enrolling in the Women's Health Initiative observational study or controlled trials. Multivariable models were used to control for sociodemographic (age, parity, race, education, income, age at menopause), lifestyle, and family history variables when examining the effect of duration of lactation on risk factors for cardiovascular disease, including obesity (body mass index [BMI] at or above 30), hypertension, self-reported diabetes, hyperlipidemia, and prevalent and incident cardiovascular disease.
RESULTS: Dose-response relationships were seen; in fully adjusted models, women who reported a lifetime history of more than 12 months of lactation were less likely to have hypertension (odds ratio [OR] 0.88, P<.001), diabetes (OR 0.80, P<.001), hyperlipidemia (OR 0.81, P<.001), or cardiovascular disease (OR 0.91, P=.008) than women who never breast-fed, but they were not less likely to be obese. In models adjusted for all above variables and BMI, similar relationships were seen. Using multivariate adjusted prevalence ratios from generalized linear models, we estimate that among parous women who did notbreast-feed compared with those who breast-fed for more than 12 months, 42.1% versus 38.6% would have hypertension, 5.3% versus 4.3% would have diabetes, 14.8% versus 12.3% would have hyperlipidemia, and 9.9% versus 9.1% would have developed cardiovascular disease when postmenopausal. Over an average of 7.9 years of postmenopausal participation in the Women's Health Initiative, women with a single live birth who breast-fed for 7-12 months were significantly less likely to developcardiovascular disease (hazard ratio 0.72, 95% confidence interval 0.53-0.97) than women who never breast-fed.
CONCLUSION: Among postmenopausal women, increased duration of lactation was associated with a lower prevalence of hypertension, diabetes, hyperlipidemia, and cardiovascular disease.

Am J Epidemiol. 2011 Nov 15;174(10):1147-58. Epub 2011 Oct 12. Duration of lactation and incidence of maternal hypertension: a longitudinal cohort study. Stuebe AM, et al.  PMID: 21997568

Never or curtailed lactation has been associated with an increased risk for incident hypertension, but the effect of exclusive breastfeeding is unknown. The authors conducted an observational cohort study of 55,636 parous women in the US Nurses' Health Study II. From 1991 to 2005, participants reported 8,861 cases of incident hypertension during 660,880 person-years of follow-up. Never or curtailed lactation was associated with an increased risk of incident hypertension. Compared with women who breastfed their first child for ≥12 months, women who did not breastfeed were more likely to develop hypertension (hazard ratio (HR) = 1.27, 95% confidence interval (CI): 1.18, 1.36), adjusting for family history and lifestyle covariates. Women who never breastfed were more likely to develop hypertension than women who exclusively breastfed their first child for ≥6 months (HR = 1.29, 95% CI: 1.20, 1.40). The authors found similar results for women who had never breastfed compared with those who had breastfed each child for an average of ≥12 months (HR = 1.22, 95% CI: 1.13, 1.32). In conclusion, never or curtailed lactation was associated with an increased risk of incident maternal hypertension, compared with the recommended ≥6 months of exclusive or ≥12 months of total lactation per child, in a large cohort of parous women.

Am J Med. 2010 Sep;123(9):863.e1-6. Lactation and maternal risk of type 2 diabetes: a population-based study. Schwarz EB, et al.  PMID: 20800156

We explored the relationships between lactation and risk of type 2 diabetes in a well-characterized, population-representative cohort of women, aged 40-78 years, who were members of a large integrated health care delivery organization in California and enrolled in the Reproductive Risk factors for Incontinence Study at Kaiser (RRISK), between 2003 and 2008. Multivariable logistic regression was used to control for age, parity, race, education, hysterectomy, physical activity, tobacco and alcohol use, family history of diabetes, and body mass index while examining the impact of duration, exclusivity, and consistency of lactation on risk of having developed type 2 diabetes. RESULTS: Of 2233 women studied, 1828 were mothers; 56% had breastfed an infant for greater than or =1 month. In fully adjusted models, the risk of type 2 diabetes among women who consistently breastfed all of their children for greater than or =1 month remained similar to that of women who had never given birth (odds ratio [OR] 1.01; 95% confidence interval [CI], 0.56-1.81). In contrast, mothers who had never breastfed an infant were more likely to have developed type 2 diabetes than nulliparous women (OR 1.93; 95% CI, 1.14-3.27) [corrected]. Mothers who never exclusively breastfed were more likely to have developed type 2 diabetes than mothers who exclusively breastfed for 1-3 months (OR 1.52; 95% CI, 1.11-2.10).
CONCLUSIONS: Risk of type 2 diabetes increases when term pregnancy is followed by less than 1 month of lactation, independent of physical activity and body mass index in later life. Mothers should be encouraged to exclusively breastfeed all of their infants for at least 1 month.

Diabetes. 2010 Feb;59(2):495-504. Epub 2009 Dec 3. Duration of lactation and incidence of the metabolic syndrome in women of reproductive age according to gestational diabetes mellitus status: a 20-Year prospective study in CARDIA (Coronary Artery Risk Development in Young Adults). Gunderson EP, et al.  PMID: 19959762 

OBJECTIVE: The objective of the study was to prospectively assess the association between lactation duration and incidence of the metabolic syndrome among women of reproductive age.
RESEARCH DESIGN AND METHODS: Participants were 1,399 women (39% black, aged 18-30 years) in the Coronary Artery Risk Development in Young Adults (CARDIA) Study, an ongoing multicenter, population-based, prospective observational cohort study conducted in the U.S. Women were nulliparous and free of the metabolic syndrome at baseline (1985-1986) and before subsequent pregnancies, and reexamined 7, 10, 15, and/or 20 years after baseline. Incident metabolic syndrome case participants were identified according to National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) criteria. Complementary log-log models estimated relative hazards of incident metabolic syndrome among time-dependentlactation duration categories by gestational diabetes mellitus (GDM) adjusted for age, race, study center, baseline covariates (BMI, metabolic syndrome components, education, smoking, physical activity), and time-dependent parity.
RESULTS: Among 704 parous women (620 non-GDM, 84 GDM), there were 120 incident metabolic syndrome case participants in 9,993 person-years (overall incidence rate 12.0 per 1,000 person-years; 10.8 for non-GDM, 22.1 for GDM). Increased lactation duration was associated with lower crude metabolic syndrome incidence rates from 0-1 month through greater than 9 months (P < 0.001). Fully adjusted relative hazards showed that risk reductions associated with longer lactation were stronger among GDM (relative hazard range 0.14-0.56; P = 0.03) than non-GDM groups (relative hazard range 0.44-0.61; P = 0.03).
CONCLUSIONS: Longer duration of lactation was associated with lower incidence of the metabolic syndrome years after weaning among women with a history of GDM and without GDM, controlling for preconception measurements, BMI, and sociodemographic and lifestyle traits. Lactation may have persistent favorable effects on women's cardiometabolic health.

Obstet Gynecol. 2007 Mar;109(3):729-38. Lactation and changes in maternal metabolic risk factors. Gunderson EP, et al.   PMID: 17329527

METHODS: This 3-year prospective study examined changes in metabolic risk factors among lactating women from preconception to postweaning and among nonlactating women from preconception to postdelivery, in comparison with nongravid women. Of 1,051 (490 black, 561 white) women who attended two consecutive study visits in years 7 (1992-1993) and 10 (1995-1996), 942 were nongravid and 109 had one interim birth. Of parous women, 48 (45%) did not lactate, and 61 (55%) lactated and weaned before year 10. The lactated and weaned women were subdivided by duration of lactation into less than 3 months and 3 months or more. Multiple linear regression models estimated mean 3-year changes in metabolic risk factors adjusted for age, race, parity, education, and behavioral covariates.
RESULTS: Both parous women who did not lactate and parous women who lactated and weaned gained more weight (+5.6, +4.4 kg) and waist girth (+5.3, +4.9 cm) than nongravid women over the 3-year interval; P<.001. Low-density lipoprotein cholesterol (+6.7 mg/dL, P less than .05) and fasting insulin (+2.6 microunits, P=.06) increased more for parous women who did not lactate than for nongravid and parous women who lactated and weaned. High-density lipoprotein cholesterol decrements for both parous women who did not lactate and parous women who lactated and weaned were 4.0 mg/dL greater than for nongravid women (P less than .001). Among parous, lactated and weaned women, lactation for 3 months or longer was associated with a smaller decrement in high-density lipoprotein cholesterol (-1.3 mg/dL versus -7.3 mg/dL for less than 3 months; P less than .01).
CONCLUSION: Lactation may attenuate unfavorable metabolic risk factor changes that occur with pregnancy, with effects apparent after weaning. As a modifiable behavior, lactation may affect women's future risk of cardiovascular and metabolic diseases.