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Two studies have been in the news recently touting the benefits of breastfeeding. The first linked breastfeeding to improved intelligence for the child. The second study claimed that the breastfeeding may reduce the risk for Alzheimer’s.
The full paper on the link between IQ and breast feeding is not available online. However the abstract can be viewed here. There are two key measures provided in the abstract to the paper. The first claimed
longer breastfeeding duration was associated with higher Peabody Picture Vocabulary Test score at age 3 years (0.21; 95% CI, 0.03-0.38 points per month breastfed)
And the second claimed
higher intelligence on the Kaufman Brief Intelligence Test at age 7 years (0.35; 0.16-0.53 verbal points per month breastfed; and 0.29; 0.05-0.54 nonverbal points per month breastfed).
The conclusion is that on the Peabody Picture Vocabulary Test with six months of breast feeding the test score is increased somewhere between 0.18 and 2.28 points. This is a test with a standardized score of 100 with a standard deviation of 15. This means that roughly 68 percent of the population falls in the range from 85 to 115 and that roughly 95 percent of population falls in the range from 70 to 130.
Similarity for the Kaufman Brief Intelligence Test the predicted improvements from the research are in the range from 0.96 to 3.18 for thee verbal test and in the range 0.30 to 3.24 for the nonverbal. This test is scaled in the same manner as is the Peabody Picture Vocabulary Test.
The results then are very small. They are much smaller than is the accuracy of the tests themselves on an individual level. IQ also is not the the sole determinate of how successful one is in life – no matter how one defines success. With such small improvement is it even worth the effort to determine if the analysis methods used in the study were appropriate?
There are numerous other reasons to breastfeed. Breastfeed by all means if one can. But increasing a child’s IQ by the levels claimed in this study does not seem to me at least to rise to the top of the list.
The study on the link between breastfeeding and Alzheimer’s was based on a recall study of 81 patients age 70 or older were selected in a very nonrandom fashion. This is a very small sample size. But even with that limitation the authors were making claims based on family history of Alzheimer’s. Consider too the age of the patients when the study was conducted. They were asking mom’s how long they breast fed when they had kids likely 40-50 years earlier. That alone raises all sorts of questions about recall issues especially when they are expected to recall not only if they breastfed, but for how long they breastfed.
A good overview and evaluation of the research can be found here.
I found the real kicker in the reported results when one of the authors is cited as follows:
Also, Dr. Fox revealed to The Independent that a similar study with a large sample of several thousand women in China found the opposite: that women who breastfed for a shorter period of time were less likely develop dementia. This, Dr. Fox says, may be down to the environmental and lifestyle differences.
In short the author is saying my results contradict those of a much larger study and all I’m going to do is speculate on the reasons for the differences. I need a better answer than that if I am going to trust the conclusion of this small study.
As a final criticism, both of these papers is hidden behind a pay-wall. The amount that most of these place charge to obtain a copy of the paper is in my mind exhortation. A few pages for $30.00 or more boggles my mind. At that price the going price for a college text book should be well over $1,000. I will say again any author who ensures substantial media publicity for their research has an obligation to make the full paper freely and readily available online.