Intensive, community-based, prospective studies have become increasingly popular for the study of the common diseases of childhood (diarrhoea, respiratory infections and malaria). The wealth of data collected in these studies permits the estimation of a range of outcome measures describing the incidence, prevalence and duration of disease. However, standard epidemiological and statistical techniques for the analysis of prospective studies were conceived with rare and non-recurrent diseases in mind, and their application to the case of common diseases is not always valid. This thesis provides a comprehensive approach to the analysis of longitudinal studies of common diseases of childhood. Starting with recommendations for successful data handling, it describes the definition, evaluation and calculation of a number of different epidemiological outcome measures, and then proceeds to investigate appropriate strategies for statistical modelling. At all stages, differences between studies of common diseases and the more familiar rare-disease studies are highlighted. The implications of these features of common disease studies for the validity of results obtained by using ‘standard’ analytic techniques are evaluated. A number of more ‘sophisticated’ analytic techniques are compared and contrasted, using criteria specifically proposed for the evaluation of statistical models in epidemiology. This evaluation is based to a large degree on illustrative analyses, using data used collected in a trial of the impact of vitamin A supplementation on the health of young children in Ghana, together with data from a rotavirus vaccine trial in Peru. Wide-ranging reviews are undertaken of the epidemiological literature on common diseases of childhood, permitting the characterisation of the range of analytic practices currently encountered. Recent advances in statistical theory are also critically described. These insights are combined to produce a series of pragmatic recommendations intended as guidance for those working on longitudinal studies of common diseases of childhood in the field
