In a prospective study comprising 10,000 subjects, 6000 subjects were put on beta carotene and 4000 were not. 3 out of the first 6000 developed lung cancer and 2 out of the second 4000 developed lung cancer. What is the interpretation of the above results ?
Ans. is 'b' i.e., Beta carotene and lung cancer have no relation to each other Prospective (coho) study is used to test the association between risk factor and disease. o Relative risk (estimated by coho study) is a direct measure of the strength of association between suspected cause and effect. o Relative risk one indicates no association between risk factor and outcome. o Relative risk more than one indicates positive association --> risk factor is causative. o Relative risk less than one indicates negative association --> that means exposure has protective role on outcome, e.g. vitamin A exposure results in decreased incidence of skin cancer. o In this question, RR is one. That means beta carotene exposure is neither causative nor protective for lung cancer.
Beta carotene is protective in lung cancer
Beta carotene and Lung cancer have no relation to each other
The study design is not sufficient to draw any meaningful conclusions
Beta carotene is carcinogenic