Experimental study findings
The Alpha Omega Trial is a randomized double-blind placebo-controlled trial carried out in 4,837 patients after a heart attack, in which the hypothesis was tested that low doses of omega-3 fatty acids reduce major cardiovascular and fatal coronary events. The advantage of such a randomized trial is that potential confounders will be evenly distributed over the different intervention groups and therefore do not influence the outcome of the trial. Besides the main hypothesis, other hypotheses could be tested on the effect of omega-3 fatty acids on different endpoints.
Observational study findings
The primary purpose of large-scale trials is to test hypotheses without potential confounding that limits the interpretation of the results of observational prospective cohort studies. However, data collected in a large-scale trial may also be used for observational research. In the Alpha Omega Trial the patients were included between May 2002 and December 2006. This data can be used to study trends in risk management and risk factors at the population level. It is also possible to study cross-sectional and prospective associations of diet and lifestyle with risk factors and indicators of health.