Design, methods and participation. Euronut SENECA investigators.

At the initiative of EC/Euronut a European Community project (SENECA) began in 1988, with 19 research groups working on the major nutritional issues affecting the growing number of elderly people in Europe. Some 2600 people born between 1913 and 1918 were studied, using strictly standardized methodology. Data have been collected on the dietary intake of these people, their nutritional status, physical activity, life-style, health and performance. It is envisaged that the SENECA project will be continued according to a mixed longitudinal design. The mean response rate in a group of 18 communities in which a non-participation study was conducted was 51%, while 60% of the non-responders were prepared to complete a non-responders' questionnaire. On the basis of the data collected from both responders and non-responders, it was found that males, non-smokers, healthy and better educated persons participated better in the SENECA study than females, smokers, persons who judged their health to be poor, and persons with comparatively poor education, respectively. Housing (having a garden), age, and marital state (single) were only of minor importance for the participation. Persons who did not eat a cooked meal daily, generally participated less, but this differed between towns. It is demonstrated how stratum-specific weighting factors can be calculated to partially remove bias due to selectivity in participation.