PurposeRecently, the concept of successful ageing has shifted from healthy ageing to active ageing, the latter emphasising even more the subjective perspective. Active agency is a marker for better functioning. However, the concept of active ageing lacks a clear definition so far. The specific aims of the study were to identify the determinants of being actively engaged in life (BAEL), to explore the changes in BAEL over 3 decades, and to explore the prognostic value of BAEL.MethodsThis is a repeated cross-sectional cohort study of older (≥ 75 years) community-dwelling people in Helsinki in 1989 (N= 552), 1999 (N= 2396), 2009 (N= 1492), and 2019 (N= 1614). The data were gathered by a postal questionnaire at each time point. Being actively engaged in life was defined by two questions “Do you feel needed?” and “Do you have plans for the future?”, which was further converted into BAEL score.ResultsAn increasing temporal trend in BAEL score was observed through the study years. Male sex, good physical functioning and subjective health, and meaningful social contacts were determinants for higher BAEL score. Active agency measured by BAEL score predicted lower 15-year mortality.ConclusionsOlder home-dwelling, urban Finnish people have become more actively engaged in recent years. The underlying causes are diverse but improved socioeconomic status observed over the study years was one of them. Social contacts and not feeling lonely were found to be determinants for being actively engaged. Two simple questions describing active engagement in life may help to predict mortality among older people.