This question landed here after two migration requests from "Medical Sciences" and "Operations Research"
I’m reading several prospective studies published in top journals where a baseline modifiable exposure was associated with a final outcome.
Just as an example might be this study.
The Authors aimed to evaluate whether oral hygiene behaviour can alleviate cardiovascular risk. For what I understand, the exposure persistency (oral hygiene behaviour) was not controlled during the study period, because any repeated assessment was performed during the follow-up.
Basically, they associated the final outcome (10 years later) to the baseline exposure.
- Is that methodologically correct?
- In a prospective cohort study, is there any need to control the exposure during the study period?