Researchers conducted a cohort study of the association betweenair pollution and asthma. The
rate ratio was 8.0, when comparing those exposed to high levelsof air pollution with those
exposed to low levels of air pollution. Which of the followingissues should the researchers
consider when making their study conclusions and when thinkingabout causality? Choose all
that apply and explain your choice.
a) The rate ratio of 8.0 indicates a strong association, whichlends support for causality
b) Strong confounding may actually be causing the strongassociation seen
c) Other studies of the same exposure—health outcome associationreported rate ratios in the
range of 1.5-3.0, less than the rate ratio of 8.0 seen in thisstudy
d) The temporal sequence of the exposure and outcome should beknown in order to draw
accurate conclusion.
