Question

C. According to Bradford-Hill, there are 9 for judging whether an association is causal. They are: strength of association, consistency, temporality, biological gradient, coherence, experiment, analogy, plausibility, and specificity. Summarized below are evidence used by the Surgeon General's Advisory Committee on Smoking and Health to support the inference that cigarette smoking causes lung cancer. Indicate the criteria (or criterion) which is/are relevant for each statement. (1 point each) 1. A review of literature identified 29 case-control studies and 7 cohort studies that had investigated the association between cigarette smoking and lung cancer. All found a positive association between cigarette smoking and increased risk of lung cancer. 2. Risk ratio of lung cancer for cigarette smokers as compared to persons who did not smoke cigarettes were 20.2, 10.0, 12.0, 15.9, 4.9, 11.7, and 9.6 in the seven cohort studies. 3. In the cohort study of Hammond and Hom, the risk ratios of lung cancer for men who smoked 0, 1-9, 10-20, 21- 39, and 40+ cigarettes per day were 1.0,5.8, 7.3, 15.9, and 21.7. 4. After taking prior duration and intensity of smoking into account, relative risks of lung cancer were lower smokers who quit smoking compared to those who did not quit after participating in a smoking cessation intervention 5. Biologically, continued smoking causes tissue damage, which over time results in the growth of cancerous cells.

Answer 1

answers

1 . first scenario of positive relation with smoking and lung cancer fall under strength of assosiation category   in which stronger the assosiation between risk factor and outcome , more likely the relationship is causal.,

2. Temporality : Is a foundational concept for causal analysis, because causal relationship unfold over time and become observable only after a certain laps of time. 7 cohort study showed causal relationship of smoking and lung cancer over a period of time.

3.Biological gradient : Greater exposure should generally lead to greater incidence of the effect. as the number of cigarette intake per day increases, chances of developing lung cancer also increases.

4. Experiment : In this, removal of expossure alters the frequency of outcome. Here relative risk of lung cancer is less in people who are willing to quit smoking compared to those who are not willing to quit smoking.

5. Plausibility :The causal consideration that an observed, potentially causal association between an expossure and health outcome may plausibly be atributed. Here continuous smoking cause tissue changes and eventually leads to lung cancer.