This article, the introduction to a collection of six related articles, describes the general rationale and design of the Berlin Aging Study (BASE). The distinguishing features of BASE are: (1) a special focus on the very old (70–105 years), (2) broad inter-diciplinarity (medicine, psychiatry, psychology, sociology and economics), and (3) sample heterogeneity achieved by local (West Berlin) representativeness. In addition to discipline-specific topics, four theoretical orientations guide the study: (1) differential ageing, (2) continuity versus discontinuity of ageing, (3) range and limits of plasticity and reserve capacity, and (4) ageing as an inter-disciplinary and systemic phenomenon. To provide a foundation and framework for the remaining articles, this paper outlines the protocols, designs, and measurement procedures of fourteen data collection sessions. In addition, information is given on the samples used for empirical analysis. Two samples from the first wave of the Berlin Aging Study are addressed in this collection of articles. The first (N = 360), uses data from the BASE Intake Assessment Protocol (Session 1). The second (N = 156), employs data from the entire 14-session full protocol of BASE. Selectivity analyses involving 22 comparison variables are reported in this paper and demonstrate that, with the exception of 12-month mortality, these two samples displayed the intended sample heterogeneity. Those results suggest that data from BASE hold high generalizability.

The Sociology and Social Policy Research Unit of the Berlin Aging Study focuses on four substantive areas: (1) life course antecedents and generational experiences, (2) later phases of the family life course, (3) action resources and social participation, and (4) economic situations and the provision of care. This paper reports results on the relationship between social and economic inequality and differential ageing, using the BASE multidisciplinary Intake Assessment (N = 360). The socio-economic position of older people is measured along three dimensions: economic resources, social status and prestige, and cultural status. Several ageing outcomes are considered, including functional physical health, cognitive functioning and mental health, overall subjective well-being, social autonomy and dependency. First, we show that old people as a group are neither socially nor economically homogeneous: very old women possess unusually low economic resources; and cohort differences in educational attainment are carried into old age. Second, cognitive functioning and mental health are positively correlated with socio-economic resources, while functional physical health is not. For women, socio-economic resources slightly affect overall subjective well-being, and are linked to the likelihood of living in a nursing home. We speculate that the wide availability of compulsory health insurance reduces social differentials in physical health and that these inequalities may determine who survives into old age.

Theoretical positions which argue for age-related and individual variation in profiles of psychological functioning and patterns of predictive relationships are reviewed in the context of the three domains investigated by the Psychology Unit of the Berlin Aging Study (BASE): intelligence and cognition, self and personality, and social relationships. To illustrate the potential of BASE, we report initial data for a small set of variables from these three psychological domains for the first wave of study participants (N = 360, age range 70 to 103 years). Our analyses of these data were targeted toward three key questions about differential psychological ageing: namely, the extent of age/cohort-related differences and individual variation within each domain, possible age differences in the structural relationships between the three domains, and subgroup variations in cross-domain profiles of functioning. Within domains, individual differences in general were very large. Chronological age accounted for a sizeable proportion of the variance only in the domain of cognitive performance. The structural relationships between the domains of psychological functioning were similar for the old and very old age groups and reflected much domain independence. Examination of subgroup variations in cross-domain profiles of functioning revealed ten subgroups. All subgroups showed an uneven, that is, age-selective group membership: five subgroups included more of the very old, two more of the old, and three were age-specific. Preliminary explorations of these subgroups suggested substantial links to selected health-related variables, supporting proposals for multi-disciplinary research into differential ageing.

Key questions in the psychiatric understanding of elderly people are the development of psychiatric morbidity, its phenomenology in old age, the differentiation between ‘normal’ and ‘pathological’ ageing, the interrelatedness of different types of mental disorders, their relation to somatic morbidity, and their consequences in daily life. Under the hypothesis of the de-differentiation of psychopathological features in old age, the relation between depression and dementia is studied. Contrary to most gerontopsychiatric research, the Berlin Aging Study (BASE) permits an analysis of these questions in a heterogeneous and primarily non-clinical community population. Initial data from the first 360 intake assessments and the first 156 intensively studied participants of BASE are presented. Results show that, even in very old individuals, depression and dementia still exhibit clearly distinctive psychopathological features. Prevalence rates in consecutive age groups show an age-related increase for dementia but not for depression. Nevertheless dementia and depression do not seem to be fully independent, because our data indicate a masking or extinction of depressive symptoms by dementia. Finally, both disorders have a similarly significant negative impact on independence, comparable to that of somatic morbidity.

The first part of this paper provides a general outline of objectives and methods of the Internal Medicine and Geriatrics Unit of the Berlin Aging Study (BASE). Based on a multi-dimensional conceptualization of health, objective and laboratory data collected about different organ systems, e.g. cardiovascular and musculoskeletal, and functional capacity are complemented by qualitative clinical diagnoses and judgements as well as self-reported health problems and functional limitations. Some of the central questions that can be addressed using these data relate to understanding the nature and processes of differential ageing. The second part of the paper includes initial analyses of inter-individual health differences in advanced old age (70 to 105 years). Initial findings indicated that heterogeneity in somatic morbidity and functional capacity was at least as large in old adults (70 to 84 years) as in very old adults (85 to 105 years), even though higher rates of somatic morbidity and lower levels of functional capacity were observed in the very old. Chronological age and morbidity as well as psychosocial and demographic factors were found to be independent predictors of functional capacity in advanced old age. Additionally, the relative importance of psychosocial factors was found to be a function of age with lower predictive ability among the very old. In conclusion, these initial findings support the hypothesis of significant health differences in advanced old age due to differential ageing.

In the present paper the focus is on structural aspects of everyday competence and its relationship with various personal resources, such as health, social status, self concept and cognition. The findings support the hypothesis that two distinct, albeit intercorrelated, components of everyday competence are differentially related to the various resources examined in this paper. The two components are a basic level of competence (BaCo) which is defined mainly by self-care related activities, and an expanded level of competence (ExCo) associated mostly with leisure and social activities and advanced instrumental activities of daily living. In general, BaCo is more strongly related to health-related resources, and ExCo is more strongly associated with behavioural, psychological and social resources. 90.6% of the reliable variance in ExCo and 82.4% in BaCo are explained by these selected resources. Furthermore, all of the age-related variance in everyday competence is accounted for by these health-related and socio-behavioural resources.