The SENECA study: potentials and problems in assessing dietary changes over time.

In 1988 a European multicenter study, named SENECA, was initiated. Nine of the original 19 participating towns in 12 European countries decided to continue the longitudinal study by conducting a second survey in 1993. The aim of the longitudinal part of the SENECA study was to provide measurements of diet, lifestyle, health and performance as such at two points in time and to analyze the direction of changes and possible interrelationships between the factors studied. For the present paper the experience with the SENECA study has been used to illustrate the problems related to nutritional longitudinal studies in different stages of dietary research. In the examples we have focused on results relating changes in body weight to energy intake and changes in total cholesterol to intakes of fat and fatty acids of participants from four SENECA sites. To examine dietary habits a modified dietary history was chosen consisting of two parts: an estimated record and a checklist of foods. The results demonstrate that the special design of the study and adaptation of methods made it possible to deal with several problems encountered in nutritional longitudinal studies in elderly people. Nevertheless the changes in diet are most likely underestimated. Consequently in the interpretation of data and further analysis we have to consider this problem as well as other remaining problems.