[The Groningen longitudinal aging study. An evaluation of functional status, well-being and need of care by others].

The central objectives of GLAS are (a) to study the associations between pathology--and related impairments and disability--on the one hand, and well-being and utilization of care among older people on the other, and (b) how these associations are affected by person-bound and environmental factors. The present paper describes the main research questions, the design and some preliminary results of GLAS. In addition, an explanatory model for well-being, derived from the theory of social-production functions (spf) is elaborated. Two major conclusions can be drawn from these results. (1) The hypotheses derived from spf are mainly supported by the results of several substudies of GLAS. (2) The cross-sectional analyses showed main effects of psychological attributes--independent of pathology and impairments--on disability and well-being; we hardly found any empirical support for the hypothesized moderating effects of psychological attributes on the associations between these concepts. We conclude with some suggestions for future research.