ABSTRACT
This review is based on analysis of original research reports in one 2006 volume from each of three major epidemiology journals: The American Journal of Epidemiology, The International Journal of Epidemiology, and the European Journal of Epidemiology. A total of 149 research reports were included in the review. The pattern that emerged from the analysis was the tendency towards large epidemiological studies that utilise all available population-based data without resort to sampling. The tendency was to use data in existing data bases instead of field data collection. Developments in information technology enabled linkage between various data bases to extend the range of hypotheses that could be tested. The transition from sample epidemiology to population epidemiology had advantages and disadvantages. The main advantage was external validity (results of the study were applicable to the population). The main disadvantage was loss of internal validity that could be achieved in small studies with higher data quality and personal familiarity of the epidemiologist with the data. It is envisioned that in the future web-based data collection will be feasible. It will also be possible to use a wider range of data routinely collected online on citizens including credit card, shopping, and other financial transactions