Research News home Producers: Ohio State has a broadcast studio with Vyvx and ISDN technology. To schedule an expert, contact Joe Camoriano, (614) 378-6478. Follow us on Facebook and Twitter. 
 
 Breast-feeding Benefits Appear to be Overstated, According to Study of Siblings Advantages of women who choose breast-feeding likely bias findings in previous research COLUMBUS, Ohio – A new study comparing siblings who were fed differently during infancy suggests that breast-feeding might be no more beneficial than bottle-feeding for 10 of 11 long-term health and well-being outcomes in children age 4 to 14. The outlier was asthma, which was associated more with breast-feeding than with bottle-feeding. The study also included an analysis of outcomes across families of different races and socioeconomic circumstances for comparison purposes, and those results matched other studies suggesting that breast-feeding’s benefits to children outweigh bottle-feeding. The lead researcher noted that there is a clear reason for that. “Many previous studies suffer from selection bias. They either do not or cannot statistically control for factors such as race, age, family income, mother’s employment – things we know that can affect both breast-feeding and health outcomes,” said Cynthia Colen, assistant professor of sociology at The Ohio State University and lead author of the study. “Moms with more resources, with higher levels of education and higher levels of income, and more flexibility in their daily schedules are more likely to breast-feed their children and do so for longer periods of time.” Cynthia Colen Previous research has identified clear patterns of racial and socioeconomic disparities between women who breast-feed and those who don’t, complicating an already demanding choice for women who work outside the home at jobs with little flexibility and limited maternity leave. Colen’s study is also rare for its look at health and education benefits of infant feeding practices for children age 4 to 14 years, beyond the more typical investigation of breast-feeding’s effects on infants and toddlers. Federal health officials have declared breast-feeding for at least six months a national priority, which could end up stigmatizing women who can’t opt to nurse their babies, Colen said. “I’m not saying breast-feeding is not beneficial, especially for boosting nutrition and immunity in newborns,” Colen said. “But if we really want to improve maternal and child health in this country, let’s also focus on things that can really do that in the long term – like subsidized day care, better maternity leave policies and more employment opportunities for low-income mothers that pay a living wage, for example.” The study is published in the journal Social Science & Medicine. Demographic differences across families that can bias studies in favor of breast-feeding include parental race, age, marital status, family income, insurance coverage, the mother’s education and employment, and whether a woman smokes or drinks during pregnancy. “When we get more advantaged moms selecting into breast-feeding and we know those traits also will affect the health outcomes, it’s not clear what’s affecting an outcome like obesity – is it breast-feeding itself or those other background characteristics?” Colen said. Colen used data from the 1979 cohort of the National Longitudinal Survey of Youth (NLSY), a nationally representative sample of young men and women who were between ages 14 and 22 in 1979, as well as results from NLSY surveys between 1986 and 2010 of children born to women in the 1979 cohort. The children were between ages 4 and 14 during the time period studied. The NLSY79 is conducted by Ohio State’s Center for Human Resource Research for the U.S. Bureau of Labor Statistics. Colen analyzed three samples: 8,237 children, 7,319 siblings and 1,773 “discordant” sibling pairs, or children from 665 surveyed families in which at least one child was breast-fed and at least one other child was bottle-fed. The children who were differently fed in the same family represented about 25 percent of the siblings in the data. For each sample, the researchers sought answers to two basic questions: Was at least one child breast-fed and, if so, what was the duration of breast-feeding? The study measured 11 outcomes that are common to other studies of breast-feeding’s effects: body mass index (BMI), obesity, asthma, hyperactivity, parental attachment (secure emotional relationships between parents and child) and behavior compliance, as well as scores predicting academic achievement in vocabulary, reading recognition, math ability, intelligence and scholastic competence. Colen constructed statistical models for the analysis. As expected, the analyses of the samples of adults and their children across families suggested that breast-feeding resulted in better outcomes than bottle-feeding in a number of measures: BMI, hyperactivity, math skills, reading recognition, vocabulary word identification, digit recollection, scholastic competence and obesity. When the sample was restricted to siblings who were differently fed within the same families, however, scores reflecting breast-feeding’s positive effects on 10 of the 11 indicators of child health and well-being were closer to zero and not statistically significant – meaning any differences could have occurred by chance alone. Email this to a friend 
 
 
 
 “If breast-feeding doesn’t have the impact that we think it will have on long-term childhood outcomes, then even though it is very important in the short-term we really need to focus on other things.” The outlying outcome in this study was asthma; in all samples, children who were breast-fed were at higher risk for asthma, which could relate to data generated by self-reports instead of actual diagnoses. Some examples of differing benefits: Breast-feeding’s beneficial influence on BMI decreased by 66 percent between siblings across families and siblings within families. The magnitude of the beneficial effects of breast-feeding for math, reading, vocabulary and intelligence declined by between 69 and 29 percent, respectively, when comparing data across families to data from within families. “Instead of comparing across families we are comparing within families, completely taking into account all of those characteristics – both measured and unmeasured – that differ by family, such as parental education, household income and race/ethnicity,” Colen explained. These same differences between samples were found in the analysis of the effects of the duration of breastfeeding. These findings have implications for health policy, she noted. “If breast-feeding doesn’t have the impact that we think it will have on long-term childhood outcomes, then even though it is very important in the short-term we really need to focus on other things,” she said. “We need to look at school quality, adequate housing and the type of employment parents have when their kids are growing up. “We need to take a much more careful look at what happens past that first year of life and understand that breast-feeding might be very difficult, even untenable, for certain groups of women. Rather than placing the blame at their feet, let’s be more realistic about what breast-feeding does and doesn’t do.” Colen co-authored the study with David Ramey, a Ph.D. candidate in sociology at Ohio State. This work is supported by a grant from the Eunice Kennedy Shriver National Institute of Child Health & Human Development awarded to the Ohio State University Institute for Population Research. # Contact: Cynthia Colen, (614) 247-8135; Colen.3@osu.edu (Email is the best way to reach Colen.) Written by Emily Caldwell, (614) 292-8310; Caldwell.151@osu.edu ||||| Read more: Click here to read a revised version of this story 
 
 Breast is still best, but the long-term benefits of breastfeeding might have been inflated, say researchers who have compared the effects of breastfeeding and bottle-feeding on siblings. 
 
 Short-term benefits, such as protection against chest and gut infections, have been clearly demonstrated in previous research and are not being questioned. 
 
 But claims that breastfeeding boosts children's IQ and protects against a range of health conditions in later life could have been based on flawed research, suggest Cynthia Colen and David Ramey of Ohio State University in Columbus, who have studied almost 700 US families. Unsurprisingly, their work has been criticised by those who support the promotion of breastfeeding. 
 
 Breast milk is more than just food; it contains antibodies and enzymes that fight germs and help babies grow. Research has shown that breastfed babies get fewer chest and gut infections in their first few months of life. 
 
 Some studies have also indicated that there are longer-term benefits on intelligence and conditions such as obesity, asthma and eczema. 
 
 Selection bias 
 
 But these studies relied on comparisons between babies born to different families, leading some people to suspect that other factors – such as income level – could be affecting the result. "Many studies suffer from selection bias," says Colen. 
 
 To address this, Colen and Ramey looked at 665 families in the US where one child was breastfed and another bottle-fed. They found that breastfeeding gave no benefits for obesity, asthma, hyperactivity, academic achievement or a child's bond with its parents. 
 
 Advice leaflets given to parents often claim the long-term benefits. 
 
 On the basis of past research, many healthcare staff also heavily promote breastfeeding to new mothers. In many Western countries, adverts for formula milk are regulated and some hospital maternity wards have policies that discourage bottle feeding. 
 
 Some argue that such schemes make women feel guilty if they are unable to breastfeed – or simply choose not to. 
 
 Fair test? 
 
 Colen and Ramey did not examine the short-term protection against chest and gut infections, because these have been most clearly demonstrated by previous research. Breast is still best, says Colen, but the findings suggest that health systems should put less effort into promoting breastfeeding and more into other ways to help poorer households, she says. 
 
 However, Mary Renfrew, who studies mother and infant health at the University of Dundee, says the study was designed too crudely to observe any effects. For instance, babies fed with a mixture of breast and formula milk would still have been classed as breastfed. "It's not a fair test," she says. Renfrew is investigating whether new mothers can be encouraged to breastfeed by paying them with shopping vouchers. 
 
 Alison Tedstone, director of diet and obesity for Public Health England, says there is good-quality evidence that "breastfeeding is associated with reduced risk of asthma during early feeding years, although the evidence for later years is not as clear". 
 
 Journal ref: Social Science & Medicine, DOI: 10.1016/j.socscimed.2014.01.027 
 
 If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.
– Breastfeeding doesn't produce the long-term benefits it's purported to, a new Ohio State University study has concluded, calling into question loads of previous research. Most older studies suffer from selection bias, lead author Cynthia Colen argues, because wealthier, better educated moms are more likely to breastfeed. Colen's research avoided that by focusing on sibling pairs in which one child was breastfed and another wasn't. The result? Breastfeeding had no effect on 10 out of 11 long-term health and well-being outcomes, and for the 11th—asthma—it actually increased risk. "I'm not saying breast-feeding is not beneficial," Colen says. But if it doesn't improve long-term outcomes, "we really need to focus on other things" that do, like maternity leave policies and subsidized day care. Colen's study doesn't examine, or attempt to contradict, previous work showing short-term immunity boosts against chest and gut infections for infants, the New Scientist explains. One breastfeeding advocate argued that the study is flawed, complaining for instance that babies fed with a mix of breast milk and formula were counted as breastfed.