The art and science of epidemiology: governed by the seasons? (Commentary)

Epidemiology is the study of ‘the distribution and determinants of health-related events in specified populations, and the application of this study to the control of health problems’.1 Observational epidemiology is bedevilled by problems of uncertainty, bias, and confounding in a world that demands certainty and clear guidance from health scientists.2 The discrepant findings between observational studies and randomized controlled trials of the associations between hormone replacement therapy and coronary heart disease (CHD), and the media and health professional responses to these discrepancies, are a particular example. Two studies3,4 published in this issue of the International Journal of Epidemiology (IJE) are, I think, important since they demonstrate examples of good epidemiological science and the art required in appropriately using epidemiological findings to affect public health policy.