http://jama.ama-assn.org/issues/v287n18/rfull/joc11087.html

I'm very interested to hear thoughts on why the effect of bf on IQ
appears, in this research, to weaken after 9 months.

 From the Comment section of the article:
"The unadjusted test scores were lower for individuals who were
breastfed for more than 9 months compared with those breastfed for 7
to 9 months. However, the adjusted means for the 2 categories were
not significantly different for any of the test scores. Thus, the
overall pattern of results suggests that no additional positive
effects are associated with breastfeeding after 9 months." (emphasis
mine)

Although I can't see how it's related, one thing that jumped out at
me in the Methods section was this:
"The mothers were asked both about duration of exclusive
breastfeeding and about total duration of breastfeeding, but 2 out of
3 mothers in the cohort gave the same answer to these 2 questions."

So there was confusion about exclusive bf vs. total duration of any
bf.  I can only guess that the questions were poorly worded -- what
mother could fail to understand the difference between "when did your
baby first eat anything besides your milk?" and "when did you stop bf
altogether?"  Here, two-thirds of mothers gave the same answer for
both questions.  Surely two-thirds of the infants were not abruptly
weaned the same day they tasted other foods/milks!  The researchers
go on:

"It is possible that the mothers distinctly remembered when they
completely stopped breastfeeding, but less clearly when they started
to supplement breast milk. It was not possible therefore to make a
detailed analysis of exclusive breastfeeding vs total duration of
breastfeeding, but a preliminary analysis showed no significant
intelligence differences between subsamples of infants who were
exclusively breastfed vs partially breastfed. Consequently, unless
otherwise specified, duration of breastfeeding refers to total
duration of any breastfeeding."

The authors also note the role of DHA and AA in IQ, and state that
the IQ differences  seen in this study might potentially be smaller
in today's infants because formula is now fortified with these
LCPUFAs.

Interesting study.  I look forward to more discussion on it.

Margaret
mom of 2, LLLL
Longmont, CO

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