CANCER AND THE DIET Flashcards
(31 cards)
what about the epidemiology of cancer suggests that the incidence is influenced by the environment?
the fact that different GI tract cancers are prevalent in different populations
e.g. gastric cancer is most present in Russia and colon cancer in the Western world
what about the diet seems to colerate with colorectal cancer levels?
dietary fat levels
what was the evidence for the five a day campaign?
the evidence showed that having an average fruit/veg intake of less than 200g is associated with increased risk of cancer
an average portion of fruit is 80g so the 5 a day was introduced
what percentage of cancers are preventable?
50%
what are the top risk factors for cancer?
smoking
alcohol/poor diet/physical inactivity/excess body weight
UV radiation
what are the bradford hill criteria for?
a group of nine principles that can be useful in establishing epidemiologic evidence of a causal relationship between a presumed cause and an observed effect
what are the 9 bradford hill criteria?
temporal association specific consistent strong association dose-response/biological gradient Experiment analogy plausible coherent
what is temporality in the bradford hill association?
the effect has to occur after the cause
what is strength on the bradford hill criteria?
the larger the association, the more likely it is causal
what is consistency in the bradford hill criteria?
consistent findings in other studies strengthens the likelihood of an effect i.e. its reproducible
what does specificity mean in the bradford hill criteria?
the more specific an association between a factor and effect, the bigger the probability of a causal relationship
what is dose-response in bradford hill criteria?
greater exposure should lead to greater incidence of effect
what is plausibility in bradford hill criteria?
a plausible mechanism between cause and effect/ there must be some idea of the mechanism
what is coherence in bradford hill criteria?
causality needs to be coherent with science as we know it
what is experiment in bradford hill criteria?
the evidence should be based on a robust study design
what is analogy in bradford hill criteria?
is there a similar causal relationship with another exposure/disease
what are the 2 main issues with establishing causality?
confounding
reverse causality
what is confounding?
when risk 1 is associated with risk 2 which is associated with an outcome, but inclinical settings risk 1 is incorrectlt associated with the outcome
what is reverse causality?
a risk factor is associated with an outcome which leads to the development of another risk factor which is incorrectly associated with the outcome
what are the pros of case control studies?
fast
cheap
good for rare diseases
what are the cons of case control studies?
recall bias
diffiuclities measuring risk
impact of diseases on risk
whst are the pros of a cohort study?
near definitive data
you can measure multiple risks and associated outcomes
what are the cons of cohort studies?
expensive long time to read out difficulties in measuring risk risk of bias risk of confounding
what are pros of RCTs?
identifies a causal relationship
randomsation reduces confounding and bias
