The January 9th 2002 Journal of the American Medical Association (JAMA)
has an interesting article on genetic modulatin of the maternal-smoking
low-birth-weight finding.
Wang, X. et al (10 authors) (2002) Maternal Cigarette Smoking, Metabolic
Gene Polymorphism, and Infant Birth Weight. JAMA, 287, 195-202. (the
January 9th copy).
Basically, women who smoke have a greater liklihood of low birth
weight infants. But the variability from one smoking mother to another
has always been high, leading researchers to speculate about modulating
variables (not just chance error). Wang et al studied women homozygous
and heterozygous for the CYP1A1 and GSTT1 genes (these genes affect
enzyme activity). Presence of the recessive gene (homo or heterozygous)
was associated with greater chance of low-birth weight, as well as
preterm birth. Without these genes, smoking had much less effect on
infant birth weight. Basically, some mothers are genetically more
susceptible to the ill effects of smoking on infant birth weight and
others are less susceptible. The study is a wonderful example of "gene -
environment interaction."
Those interested in statistics would also note how medical journals
are properly using confidence intervals. A line from the article .. "For
the ever smokers, the mean birth weight was 280g lower (95% confidence
interval [CI], -413 to -147) ..." To be sure, CIs are more useful in a
well established area of research where the nill hypothesis (viz, null
hypothesis = no difference) is not a reasonable possibility. I tried to
get a summary of the article from jama.com but could only find this
week's articles.
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John W. Kulig [EMAIL PROTECTED]
Department of Psychology http://oz.plymouth.edu/~kulig
Plymouth State College tel: (603) 535-2468
Plymouth NH USA 03264 fax: (603) 535-2412
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"One word of truth outweighs the whole world."
Russian proverb
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