Day 017 - 25 Jul 94 - Page 51


     
     1        A.  I think this is a problem with all of these studies.
              We have talked about this on several occasions.  There is
     2        the problem of trying to devise the ideal questionnaire to
              ascertain what people are really eating and its relevance.
     3
         Q.   They say: Finally, CPS 2 participants" whatever those "are
     4        on average more educated and affluent than the US
              population as a whole.  Greater access to medical care and
     5        screening may contribute to their lower mortality rates
              from colon cancer.   While these differences may influence
     6        the ability to generalise our findings to  groups of low
              socioeconomic status, they are unlikely to compromise
     7        internal validity."
              A.  Yes.  I think what I would take from this study is
     8        that it is a study which originally looked at 764,343
              people which is an extremely large study.  If you speak to
     9        statisticians about any assessment of cancer treatment or
              cancer risk, the larger the number of people that you have
    10        the less likely are you to have errors which may creep in
              because of possible chance.  We were discussing this
    11        morning about statistics.  So the greater the size of the
              study the less are the chances that the result will appear
    12        purely chance.
 
    13   Q.   In the lights of that I would, if you will forgive me,
              just like, I think you have answered the question I was
    14        going to ask but nonetheless I would like to read the
              abstract, if I may. "Background - diet, physical obesity,
    15        asprin use and family history may all modify the risk of
              colon cancer".  Dr. Arnott, the word "modify" in this
    16        context does not mean reduce, does it?  It does not mean
              moderate?
    17        A.  No, because they are talking about obesity which may
              in fact increase the risk.  Family history of course may
    18        be relevant in terms of increasing the risks.
 
    19   Q.   It means qualify it one way or the other?
              A.  Absolutely, yes.
    20
         Q.   "Modify the risk of colon cancer, but few epidemiologic
    21        studies are large enough to examine these factors
              simultaneously.  Purpose -- we have respectively assessed
    22        the relationship of diet and other factors to the risk of
              fatal colon cancer.  Methods -- using data from cancer
    23        prevention study II an ongoing prospective mortality
              study, we  studied" as you said, Dr. Arnott "764,343
    24        adults who in 1982 completed a questionnaire on diet and
              other risk factors and did not report cancer or other
    25        major illness.  We assessed mortality through August 1988
              and identified 1150 deaths from colon cancer. 
    26        Multivariated analyses were used to compare these case 
              persons with 5,746 matched control subjects drawn from the 
    27        cohort.   Results -- risk of fatal colon cancer decreased
              with more frequent consumption  of vegetables and high
    28        fibre grains.  P for trend equals .031 and .0012 in women.
                The relative risk RR for the highest versus quintile of
    29        vegetable intake was .76 in men 95 per cent confidence
              interval equals .57 to 1.02, and  .62 in women 95 per cent
    30        CR equals .45 to .86.
 

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