Internal and external validity of cohort studies

I participated with pleasure in discussions on 30 September 2011 in Warsaw during the ‘Differences in Health in the Polish population’ Conference, which aimed at critical assessment of first baseline results from the PONS study, a pilot prospective cohort established in Poland. The PONS study results from the ‘Closing the Health Gap’ Report recommending an attempt to start building in Central and Eastern Europe a network of prospective cohort studies with a biobank for the sustainable monitoring of health changes and effectiveness of health interventions in countries with much worse health indicators than Western Europe.