Day 017 - 25 Jul 94 - Page 24
1 diagnosis and, in addition, a dietary history covering
frequency and quantity of fat consumption six months
2 before interview, which for most of the cases would have
been close to the diagnosis of breast cancer. The 24 hour
3 recall (which gave the lowest estimates of intake of the
three dietary methods) alone gave significant case-control
4 differences in the study overall, with consumption of
total calories and saturated fat being greater among the
5 cases: total fat intake, however, though higher, was not
significantly higher than among the controls. No
6 appreciable dose-response relation with fat was found by
any method.
7
The study by Lubin and his colleagues (1981), also carried
8 out in Canada, reported a higher intake of beef, pork and
butter among women with breast cancer than population
9 controls. However, evaluation is made difficult by the
fact that a large number of controls failed to cooperate
10 (28%) and those who did, unlike the cases" -- those are
the people who have the disease, are they not?
11 A. That is correct.
12 Q. "... were interviewed at home, thereby providing
opportunities for bias". May I pause there? Does that
13 illustrate one of the problems with case controlled
studies, that you cannot guarantee that the controls are
14 going to do what is asked of them?
A. No. As I said earlier on, often the controls are
15 found by mailshot and these people are derived from a
register of the population, and what they try to do is to
16 select patients or people who are of a similar age
distribution. For example, in breast cancer they are all
17 women, of course, but similar age distribution to those
who actually have the disease.
18
Now, in a study where 28 per cent of people did not
19 respond or did not participate, one, therefore, wonders
how relevant the results can be in the remaining 72 per
20 cent of patients of people when you actually have a
sizeable proportion actually not participating in the
21 study whom you have matched to the patients who actually
have the disease. So, there is a big slice of information
22 missing from such a study. It, therefore, inevitably
casts doubt on the validity of the conclusions which may
23 be drawn from that particular study.
24 Q. Without anything sinister in mind, I would like to leave
out the rest of that paragraph, except if one reads it,
25 one can see how difficult it is to interpret it. At the
start of the paragraph: "Over a period of several years",
26 can I start there?
A. Yes.
27
Q. Have you got that?
28 A. Yes. "Over a period of several years all women
admitted with suspected cancer to the Rosewell Park
29 Memorial Institute in Buffalo, New York, were routinely
questioned about their diet. Graham and his colleagues
30 (1982) analysed the data collected on fat consumption from
a large group of women with a confirmed diagnosis of
