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Rapid Responses: Rapid Responses published:
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Does 1979 data hold up?
- Veronica G. (Ronnie) Falcao (6 October 2006)
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Defining breastfeeding properly could change conclusions
- Rachel Myr (6 October 2006)
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Dose of human milk not specified
- Marsha Walker, RN, IBCLC (6 October 2006)
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Whose results are biased?
- James E Akre (7 October 2006)
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mathematical manipulation
- NAOMI BAUMSLAG (7 October 2006)
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Distribution of sample by length of feeding
- Anna-Louise Hale (7 October 2006)
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No cognitive advantage for artificially fed infants given some breastmilk
- Nina J Berry (7 October 2006)
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Nice stats, too bad about the biology
- Alison Barrett (10 October 2006)
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FAS is a alcohol problem
- Mieke Siebelink (13 October 2006)
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Breastfeeding and Intelligence Not Demonstrated
- James W. Prescott, Ph.D. (19 October 2006)
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Breastfeeding and Intelligence article has methodologic flaws
- Melissa C. Bartick (27 October 2006)
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Mozart effect as confounding factor
- Jeanne A Pawitan (6 November 2006)
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Lead, breast milk & intelligence
- Tom Hughes-Davies (8 November 2006)
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Missing key qualifications in title and abstract!
- Abbas Esmaeili (13 December 2006)
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Veronica G. (Ronnie) Falcao, midwife 94041
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Although this study was just published, it appears that it was based on data collected in 1979; it is hard to know whether the data collection standards from 1979 would hold up against today's standards. It is not surprising that there would be parental influences on intelligence, but the question is whether parental influences account for all of the increase in intelligence that is observed in breastfed babies. Other studies based on more modern data have found that there appears to be an increase in intelligence that is independent of parental IQ: Clin Pediatr (Phila). 2004 Oct;43(8):753-61. Influence of breast-feeding and parental intelligence on cognitive development in the 24-month-old child. Gomez-Sanchiz M, Canete R, Rodero I, Baeza JE, Gonzalez JA. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=15494884&query_hl=1&itool=pubmed_docsum Competing interests: None declared |
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Rachel Myr, midwife NO-4604 Kristiansand, Norway
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The authors of this study conclude, seemingly without a doubt, that the observed correlation between being breastfed and performing better cognitively is attributable to maternal intelligence, based on the fact that mothers who stated they had ever breastfed their children at all, got higher scores on a military intelligence test apparently administered in connection with the study from which all the data were gleaned. In the article, a breastfed child is defined as one whose mother reported EVER having breastfed, thus including those children who may have had one feed of colostrum on the first day of life, as well as children who may have been exclusively breastfed for a considerable period, though since the data are from the US with its iatrogenic societal deficiency in breastfeeding, the latter group is likely to be very small indeed. Most of the so-called breastfed children in this data set were likely partially breastfed for a time period measurable in weeks, not even months. Drawing such pat conclusions about the effect of breastfeeding under such circumstances is like drawing conclusions about the effect of not smoking based on outcomes in a population where some people claimed to have smoked continuously and some only partially, occasionally, or intensively for a short period. I use this comparison purposely, because it is innately obvious in 2006 that 'not smoking' is to be considered the norm, while 'smoking' is health-threatening behavior. I await with impatience the day when all those concerned with public health view breast- and artificial feeding along such a dichotomy. This might even force researchers who expect to publish their work, to define their concepts so that their research contributed something more meaningful to what we already know. As it is, even the reviewers in the BMJ seem oblivious to the significant bias (equating 'any' breastfeeding at all with exclusive breastfeeding for many months) which permeates the entire premise for the article in question, and renders the conclusions, at least for this reader, meaningless. rachel@myr.no Competing interests: Employed as staff midwife and breastfeeding specialist in public hospital in Norway |
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Marsha Walker, RN, IBCLC, Nurse, Lactation consultant National Alliance for Breastfeeding Advocacy, Weston, Massachusetts 02493 USA
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Declaring that breastfeeding has no effect on intelligence in children based on the results of this study is highly misleading. The study fails to adequately delineate the dose of human milk received by children labeled as breastfeeding. The duration of breastfeeding is meaningless unless we know the degree of exclusivity of those defined as having been breastfed. "Breastfed" children in this study are lumped together no matter if they breastfed once a day for 7 days or exclusively for six months. Failure to establish an exclusively breastfed control group eliminates any meaningful conclusion. I respectfully suggest that the editors of BMJ require researchers to include an exclusively breastfed control group in research such as this prior to publishing such a skewed and unreliable article. Competing interests: None declared |
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James E Akre, Author; Public Member, Board of Directors, International Board of Lactation Consultant Examiners 1232 Confignon, Geneva, Switzerland
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Based on everything we've learned in the last quarter-century about breast milk and breastfeeding, the authors' conclusion seems totally counter-intuitive. According to Siegel (Siegel DJ, The Developing Mind, 1999), at birth the infant's brain is the most undifferentiated organ in the body. If genes and early experience shape the way neurons connect to one another and thus form the specialized circuits that give rise to mental processes, it seems reasonable to conclude that whether we fire this process with a food based on the milk of an alien species or in a manner that is consistent with who and what we are as a species will make a significant difference in developmental outcome. Attempting to measure this difference retrospectively is challenging, of course, all the more in the absence of a clear fix on what kind of breastfeeding was being practiced by the children in the study cohort. What struck me first about the study and its analysis is the age of the data; or perhaps I should rather say the implications of the age of the young people in question, 14 to 22, who were first interviewed in 1979 and the feeding practices common during the specific period. The study cohort was born between 1957 and 1965. In 1957 - a year after La Leche League was founded in suburban Chicago - the national ever-breastfed rate in the US was about 28% (compared to 70% at present). I don't have a figure handy for duration, but my assumption is that it was correspondingly low, especially in the light of contemporary national (American Academy of Pediatrics) and international (WHO) recommendations. This period was also marked by infants being commonly fed semi-solids earlier rather than later - indeed, the earlier the better - as part of conventional child-feeding wisdom. In the USA of the 1950s and 1960s it was customary to start complementary feeding before one month of age with cereal preparations, strained vegetables and fruits, and eggs and meat. Although duration of breastfeeding is dealt with briefly, there is no significant attempt to define what kind of breastfeeding, including duration or degree of exclusivity, or what kind of feeding practices in general, were common among the study population. The definition of "breastfeeding status" (Table 1) is a not especially informative one- dimensional divide between "not breastfed" and "breastfed". In their discussion, the authors point out that “only a small proportion of the many studies that have shown a positive effect of breast feeding on children’s cognitive ability control for material intelligence”. They conclude by saying that “studies that do not control for maternal intelligence will probably give biased results”. Under the circumstances, I would observe that studies that do not control for initial exclusivity and overall duration of breastfeeding will probably also give biased results. Competing interests: None declared |
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NAOMI BAUMSLAG, Clinical ProfessorPediatrics Georgeorgetown University Medical School consultant physician 20817
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Dear Editor 1. The paper in the BMJ October 4th,2006 by Der et al” the effect of breastfeeding on intelligence in children; prospective study, sibling pairs analysis, and meta-analysis October 4 is fundamentally flawed especially because of it’s the loose definition of breastfeeding. The definition of breastfeeding used could mean once a day or just once. There was no effort to differentiate between exclusive breastfeeding and other forms of feeding including mixed and exclusive breastfeeding. Suggest that the study be discounted totally on the basis of the unacceptable epidemiological definition of breastfeeding and exclusion of premature infants. The duration and frequency of breastfeeding affects the dose of breastmilk and this has been minimized instead of explored. Furthermore the study used a hodge podge of old data. 2. The meta studies cited were very selected and data was of mixed quality . Some of the data was recall data even up to one year which alone is problematic and not generalizable. 3. The authors attribute intelligence to the mother. Are so called breastfeeding mothers more intelligent than infants of formula fed mothers? Do fathers not have any role in all of this? Are the authors suggesting breastfed mothers are more intelligent than mothers who don't breastfeed? Were the mothers single or married? If single then I suppose you could postulate fathers don’t count. There are a lot of reasons mothers choose not to breastfeed including formula companies’ freebies and advertisements. All this has been researched.1 In my opinion this is selective mathematical manipulation is not worth the paper it is written on and does nor prove anything. Naomi Baumslag MD MPH Clinical Professor Georgetown University Medical School phone 301 4699210 address 7100 Oak Forest Lane Bethesda MD 1 Baumslag N.and Michels D.(1995) Milk Money and Madness Culture and Politics of breastfeeding. Bergin and Garvey, Westport Connecticutp Competing interests: None declared |
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Anna-Louise Hale, Breastfeeding Peer Support 24 Maywood Close, Kenton, Newcastle Upon Tyne, NE3 3QT
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I really just have a query. Your groups for duration of breastfeeding are focused on durations of less than 6 months. What was the distribution of your breastfeeding sample by duration? Competing interests: None declared |
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Nina J Berry, PhD Candidate Centre for Helath Behaviour and Communication, University of Wollongong, NSW AUSTRALIA 2250
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Der, Batty & Deary (1) conclude that breastfeeding has no impact on cognitive development. While this study has effectively controlled for a number of confounders, it may suffer from misclassification bias. This is a problem that is common in the literature addressing effects of infant feeding in spite of the fact that internationally agreed definitions were developed over fifteen years ago (2).
Furthermore, the World Health Organization has recently taken the position that exclusive breastfeeding for at least four months followed by continued breastfeeding until at least twelve months is a prerequisite of physiologic growth and development (11). This means that research into the effects of infant feeding ought to take exclusively breastfed infants as the referent group if it is to clearly identify the effects of infant feeding on health outcomes (12).
The authors distinguished only two groups of infants, those never breastfed and those ever breastfed. Given that only 3% of mothers reported exclusive breastfeeding at four months, it is not unreasonable to infer that this study misclassified a number of infants as 'breastfed' who would have been predominantly artificially fed. It is likely that many of these infants did not receive a clinically significant dose of breastmilk or breastfeeding. It is not surprising, then, that it found that “breastfeeding” did not significantly impact on the cognitive development of artificially fed infants. As Der, Batty & Deary (1) point out there are relatively few high quality studies of the effects of infant feeding that control for maternal intelligence and amongst those that do, evidence of cognitive deficit amongst artificially fed infants is not convincing. However, it is important to note that of the eight studies that the authors included in their meta-analysis (3-10) only five included a clear definition of breastfeeding and none of them included a fully or exclusively breastfed referent group. This demonstrates that measurement error is common in the literature in this field and helps to explain the controversy that surrounds research into the effects of infant feeding. Controlling for 'child's environment' is also problematic because it may not be an independent variable. As noted by Hay et al. (4) – which the authors cite - there is evidence that breastfeeding itself increases maternal sensitivity and responsiveness. It does not follow from this research that artificially fed infants are not at increased risk of cognitive deficit. The only conclusion that can be drawn from this study is that artificially fed infants who are fed some breastmilk are not conferred with a cognitive advantage over their completely artificially fed counterparts. Further high quality research is needed in this area. Researchers should use internationally accepted definitions of breastfeeding (2) and compare infants who are breastfed according to World Health Organization recommendations (13) with infants who are fed a commercial breastmilk substitute. Nina Berry BA/BEd(Hons) DipArts(Phil)
Competing interests: None declared |
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Alison Barrett, Obstetrician and Gynaecologist Hamilton, New Zealand
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Der et al. confidentially conclude that “while breast feeding has many advantages for the child and mother, enhancement of the child’s intelligence is unlikely to be among them.” In their rigorous statistical analysis, they appear to have overlooked the possibility that they didn’t find a relationship between breastfeeding and the child’s cognitive development – when one exists – while at the same time assuming that the previous studies showing effects of breastfeeding on cognition are guilty of the opposite. While no study to date has shown children to be intellectually advantaged by not being breastfed, this is dismissed by the authors as “publication bias”. They point to the size of their own study, and to the number of confounders independently controlled for, as the best indication of the validity of their conclusions. Rather than using statistics to explain away the significance of an observed effect, we need, first, to consider the probability that the effect is real. Is it biologically plausible that babies who are fed with human milk achieve optimal neurological development? Consider the World Health Organization’s recently released Multicentre Growth Reference Study. This study, based on breastfeeding as the biological norm, showed that babies who are breastfed exclusively for around 6 months and continue to be breastfed for up to 2 years and beyond while complementary foods are added, have marked, measurable and statistically significant differences in anthropomorphic growth compared to artificially fed babies (1). If their bodies grow differently, why shouldn’t their brains develop differently as well? If breastfed babies’ brains develop differently, then why did Der et al. fail to find a difference in the cognitive outcomes they were assessing? The answer comes in looking at the data used and the population described. In data obtained from a US national longitudinal survey of youth, the children's mothers who didn’t breastfeed achieved a raw score of 26 on the Armed Forces Qualifying Test; and the children's mothers who did breastfeed, a whopping 46. To put this into perspective, a score of 31 is the cut-off for admission to the US military. The standard errors in these two groups are both exceedingly small, thus we can be very confident that these two groups clearly represent two very different subsets of women. Mothers who admit they fully artificially fed their babies are at a significant cognitive disadvantage in comparison to mothers who claim to have “breastfed". The authors give little or no consideration to defining what is meant by "breastfeeding" which may have occurred for an unspecified length of time (2 days or 2 years), in an unclassified manner (exclusively or not) and with an undefined mode of breast-milk delivery (breast or bottle). Each of these has biological meaning. The danger of using such different subsets to draw conclusions is that the statistical analysis of some of these confounders while simultaneously ignoring others may bury the important but smaller differences that exist within them. This has happened before. Another study published last month, involving two of the same authors using the same data set, similarly suggested that mothers who smoke during pregnancy don't put their children at any cognitive risk. This, the authors explained, is because any perceived differences in IQ between children of smokers and non-smokers was accounted for by genetic differences in the IQ of the mothers together with the mothers’ educational achievement (2). Presumably, the same could be "proven" statistically for drinking alcohol in pregnancy…that fetal alcohol effects aren't due to how much alcohol the mother drinks, but due to her intelligence. If overwhelming numbers of low-IQ women drink during pregnancy, the biological effects on the fetus of drinking alcohol might be said to be explained "more by intelligence" than by drinking alcohol. A sibling comparison could factor out these between-mother differences. Yet, a sibling study is only feasible if there is sufficient within-family variation in breastfeeding prevalence or duration (3). This variation is not commented on by the authors of this particular study, although it has been determined in a previous study, which found statistically significant effects (3). If the bulk of the "breastfeeding" group includes a population of short-duration non-exclusive breastfeeders, there won't be much difference to detect. And even if sufficient variation were present, a sibling study doesn't completely eradicate the possibility of type 2 error, especially if errors occur in measurement of a variable (such as an IQ test measuring "intelligence"). If measurement errors are large enough, measurement bias can completely mask the true relationship between breastfeeding and cognitive outcome (3). A further problem that plagues all such sibling studies is the reasons why siblings differ in their breastfeeding histories. It could be that one sibling was critically ill, or that the mother was ill and on medication contraindicated in breastfeeding. In any case, it is very unlikely that the decision to breastfed one child more than another is made randomly. The unobserved factors that lead a mother to breastfed two children differently can have effects that are far-reaching, psychologically profound, yet completely undetectable by any statistical analysis. What this study does point out – far from being the generalizable result to other developed countries suggested by the authors – are, to put it bluntly, the marked inequalities that exist in the USA between the haves and the have-nots: children who are breastfed have intelligent mothers, and children who aren’t breastfed have not. The real tragedy will occur if, as a result of the considerable media attention this study has garnered (4, 5, 6, 7), these children continue to be further disadvantaged – cognitively and otherwise – by not being breastfed. References 1. de Onis, Mercedes. Foreword Acta Pædiatrica, 2006; 450: 5_/6. 2. G. David Batty, Geoff Der and Ian J. Deary Effect of Maternal Smoking During Pregnancy on Offspring's Cognitive Ability: Empirical Evidence for Complete Confounding in the US National Longitudinal Survey of Youth Pediatrics 2006;118;943-950. 3. Eirik Evenhouse and Siobhan Reilly, Improved Estimates of the Benefits of Breastfeeding Using Sibling comparisons to Reduce Selection Bias Health Services Res 2005;40: 1781-1802. 4. Doubt on breast-IQ link http://www.thewest.com.au/default.aspx?MenuID=27&ContentID=8981 5. Study says breastfeeding has no impact on a child's intelligence hhttp://www.cbc.ca/cp/health/061005/x100510. 6. Breastfeeding: no IQ boost http://www.health24.com/news/Parenting_Child_health/1-937,37830.asp 7. Breastfeeding Does Not Make Baby More Intelligent http://www.medicalnewstoday.com/healthnews.php?newsid=53355 Competing interests: None declared |
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Mieke Siebelink, Labor and postpartum assistent and maternity Aid in Buller Hospital Buller Hospital . Westport . New Zealand
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We adopted two children with the Fetal Alcohol problem. I studied on the topic and am convinced that FAS has nothing to do with the intellectual status of the parents, but is solely an alcohol problem. Every expectant parent should know the danger of alcohol in pregnancy. A small amount of alcohol can damage your child forever. Competing interests: None declared |
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James W. Prescott, Ph.D., Retired Home 19958
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The article on Breastfeeding and IQ in the BMJ was read with much interest, however, the duration of breastfeeding is far too short to expect any significant effect on intelligence, as claimed. The authors report "that the median duration of breastfeeding is three months and the 95th percentile is 14 months". This duration of breastfeeding is far too short to test the hypothesis that there is a link between breastfeeding and IQ.
There is increasing evidence that the long term health benefits of breastfeeding is to be found in the emotional-social-sexual domain rather than in the IQ domain and it takes breastfeeding bonding for 2.5 years to optimize brain-behavioral development to realize these emotional-social-sexual developental effects. The studies by this author on 26 tribal cultures with weaning age of 2.5 years or greater have documented that 77% of these cultures are rated low or absent in depression/suicide; and that a statistically significant difference exists in rated suicides between cultures with WA of 2.0 years or less v 2.5 years or greater indicating a formative period of brain development that would account for these effects. There are, of course, no tribal cultures that do not breastfeed. It takes a particular kind of culture that supports a mother breastfeeding for 2.5 years or longer. See http://www.violence.de/prescott/politics-trust.pdf and http://www.violence.de/prescott/ttf/article.html; http://violence.de/prescott/ttf/cultbrain.pdf Clearly, this kind of data on breastfeeding for "two years of age and beyond", as recommended by WHO and UNICEF (Innocenti Declaration, 1990), does not exist in any of the national registers on breastfeeding, unless the authors have information to the contrary. Only 2.7 percent of American mothers are breastfeeding at two years of life and only 1.0 percent at 2.5 years of life. (NHANES 111,1988--94) (Third National Health and Nutrition Examination Survey). (Hedeger, 2001). The effects of extended breastfeeding on reducing breast cancer was reported by Zheng, et al (2000). They report: "For women who breastfed for more than 24 months per child, the odds ratio was 0.46 (95% confidence interval (CI): 0.27, 0.78) when compared with those who breastfed for 1–6 months per child. A significantly reduced risk of breast cancer was also found for those whose lifetime duration of lactation totaled 73–108 months (odds ratio = 0.47, 95% CI: 0.23, 0.95) and for those who breastfed for 109 months (odds ratio = 0.24, 95% CI: 0.11, 0.53)". It is time that modern neurodiagnostic tools of MRI, fMRI, PET scans and other modern quantitative methods of brain evaluation be employed to assess differences in brain structure and function in young adults who have been breastfed for "two years and beyond" v non-breastfed controls. There is an equal need to record the weaning age of every child and make it a part of the immunological record and a nation's vital statistics record. There is an urgent need to establish a new international growth record that includes parameters of brain development and function, as they are not now a part of the breastfeeding record to evaluate the nutritional effectiveness of infant formula milk (WHO, 2001). http://www.who.int/inf-pr-2001/en/note2001-07.html., The psychobiology of breastfeeding takes time that is not recognized by modern human cultures and that it takes a particular kind of culture to support mothers breastfeeding for "two years of age and beyond". The modern human culture has lost its cultural heritage and is not one of these cultures. References Hediger, M (2001). The Third National Health and Nutrition Examination Survey, 1988-1994). Personal Communication. National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH).Bethesda, MD. Prescott, J.W., Read, M.S., Coursin, D. B. (Eds).(1975) Brain Function and Malnutrition: Neuropsychological Methods of Assessment. John Wiley, New York. Prescott, J.W. (1997). Breastfeeding: Brain nutrients in brain development for human love and peace. Touch the Future. Spring . http://www.violence.de/prescott/ttf/article.html Prescott, J.W.(2002) How Culture Shapes the Developing Brain .Touch the Future . Spring http://violence.de/prescott/ttf/cultbrain.pdf Prescott, J.W.(2005). Prevention or Therapy and The Politics of Trust: Inspiring A New Human Agenda. Psychotherapy and Politics International. 3(3): 194-211. http://www.violence.de/prescott/politics-trust.pdf Tongzhang Zheng, Li Duan, Yi Liu, Bing Zhang, Yan Wang, Yongxiang Chen, Yawei Zhang and Patricia H. Owens (2000). Lactation Reduces Breast Cancer Risk in Shandong Province, China. American Journal of Epidemiology Vol. 152, No. 12 : 1129-1135 WHO/UNICEF. (1990) Innocenti Declaration: On the Protection, Promotion and Support of Breastfeeding. Florence, Italy--1 August WHO (2001). The Optimal Duration of Exclusive Breastfeeding. Results of a WHO systematic review.Note for the Press #7.Geneva, http://www.who.int/inf-pr-2001/en/note2001-07.html. Competing interests: None declared |
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Melissa C. Bartick, physician (internist) Cambridge Health Alliance, USA 02139
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The article by Der, Batty and Deary has flawed methodology, making any conclusion about the effect on breastfeeding and intelligence premature. In this study, breastfeeding is not defined. It can mean anything from one breastfeeding a day, to exclusive breastfeeding (8-12 breastfeedings per day). The authors used duration as a proxy for dose, which cannot be done. We should treat breastfeeding as we treat all other drugs or treatments; we would never publish a study on a drug where the dose was not specified. Duration is not an appropriate proxy for dose; nor would it be considered so for any other intervention studied. Furthermore, the median duration of breastfeeding was only 3 months in this study, when the recommended duration of breastfeeding is 1-2 years. Very few children in this study even reached recommended levels-- the 95th percentile here was only 14 months. Finally, the study excluded the low-birthweight babies, most of whom are premature. This is a group known to be affected by breastfeeding, as breastmilk is especially important for neurologic and eye development in this group. It is important that breastfeeding research and its peer review process be rigorous. It is clear that this study was not reviewed by people with expertise in breastfeeding research-- such reviewers would never recommend publishing a study with these serious methodologic flaws. All we can conclude from this study is that breastfeeding for a very short duration, with unspecified doses of breastmilk, in non-low birthweight children, had no effect on intelligence. To really determine the effect of breastfeeding on intelligence, one must carefully define breastfeeding, include a population of exclusively breastfed infants, and study infants whose breastfeeding duration approached recommended levels. Low birthweight infants should be studied as a separate group. Competing interests: None declared |
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Jeanne A Pawitan, Professor Department of Histology, Faculty of Medicine, University of Indonesia, Jakarta10430, Indonesia
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Dear editor, I would like to comment the article in BMJ 2006;333:945 by Der G, Batty GD, Deary IJ. Effect of breastfeeding on intelligence in children: prospective study, sibling pairs analysis, and meta-analysis. (1) I think that it is widely known that music such as Mozart sonata K448 might have beneficial effects on IQ, especially spatiotemporal IQ. (2-4) However, I did not see that it was included as a confounding factor, or is it included in the short form of the home observation for measurement of the environment scale?. Many young parents, especially those with high education expose their babies to Mozart, even before the baby was born. References: 1. Der G, Batty GD, Deary IJ. Effect of breastfeeding on intelligence in children: prospective study, sibling pairs analysis, and meta-analysis. BMJ 2006;333:945. 2. Rauscher FH, Shaw GL, Ky KN. Listening to Mozart enhances spatial- temporal reasoning: towards a neurophysiological basis. Neurosci Lett. 1995;185(1):44-7. 3. Bodner M, Muftuler LT, Nalcioglu O, Shaw GL. FMRI study relevant to the Mozart effect: brain areas involved in spatial-temporal reasoning. Neurol Res 2001;23(7):683-90. 4. Hughes JR. The Mozart Effect. Epilepsy Behav 2001;2(5):396-417. Jeanne Adiwinata Pawitan, M.D., PhD
Competing interests: None declared |
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Tom Hughes-Davies, Paediatrician SP6 2EJ
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Of 172 normal American 5 year olds 71 had a lifetime average blood lead of over 10micrograms/decilitre. None of these had an intelligence quota of over 100, and all 6 children with IQ over 120 had a level under 5 microg/dl (1, figure 2). Thirty years ago many mothers had lead in their bones. Perhaps the possibility of lead in their milk should be considered in relating breast feeding to intelligence. 1. Canfield RL, Henderson CR, Cory-Slechta DA et al. Intelligence impairment in children with blood level concentrations below 10microgram/dl. New Engl J Med 2003;348:1517-26. Competing interests: None declared |
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Abbas Esmaeili, Medical Doctor, Copy Editor of JRMS Isfahan University of Medical Sciences, Isfahan, Iran.
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Der and colleagues show that the relationship between breastfeeding and intelligence (IQ) in children is strongly confounded (and almost eliminated) by the positive relationship between maternal IQ and breast feeding.1 The difficulty of defining ‘breast feeding’ in this study (acknowledged by the authors) is, however, a major weakness. Neither frequency nor duration could be measured. The term “breast feeding” alone is not sufficient to describe the numerous types of breastfeeding behavior.2 Information about exposure, i.e. breast feeding frequency, duration and intervals plus other information (such as type, timing and amount of other feedings) are essential to evaluate the outcome of interest (IQ). I was also disappointed by the editing of this paper. In my view, the conclusion of the abstract “Breast feeding has little or no effect on the intelligence of children” seriously overstates the findings by omitting key qualifications. While at the end of the article the editors comments in “What this study adds” are slightly nuanced, they again mislead. How readers approach our research reports matter. There is variability in how journal articles are read.3;4 Practitioners may read them to advise social policies or to shape interventions with families. Many time-pressed readers only read the title and some of them will continue reading the abstract only if the title attracts their interest. Only, a minority read them from the first word of the title through the last word of the discussion. In the breast feeding and intelligence article, those who only read the abstract might be misled into considering that any kind of breast feeding pattern has little or no effect on intelligence in all children because they have missed key qualifications. You may consider this as an error of the reader, but the consequences pull out into family practice and policy with implications for people's lives. On the other hand, I argue that this is an error on the part of authors. There is a concern about how the authors of this article have not presented the finding of short duration of breast feeding in non-low birth weight children in the abstract. Furthermore, the misleading title could have been changed to a more reflective one such as: Effect of short duration breast feeding on intelligence in non-low birth weight children. I believe every effort should be made to ensure that each section accurately reflect the real concept behind the article. Abbas Esmaeili, MD
Reference List 1. Der G, Batty GD, Deary IJ. Effect of breast feeding on intelligence in children: prospective study, sibling pairs analysis, and meta-analysis. BMJ 2006;333:945. 2. Labbok, M and Krasovec, K. Toward consistency in breastfeeding definition. Studies in Family Planning, Vol.21, No.4, Jul.- Aug., 1990 21(4), 226-230. 1990. 3. Misiewicz G. How to Read a Paper: T Greenhalgh. London: BMJ Publishing Group, 2001, {pound}16.95, illustrated, pp 222. ISBN 0 7279 1578 9. Gut 2002;50:442. 4. Walker AJ. Refracted Knowledge: Viewing Families Through the Prism of Social Science. Journal of Marriage and Family 2000;62:595-608. Competing interests: None declared |
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