The Longitudinal Aging Study Amsterdam (LASA)

Motivation
Changes in bodily functions and in various aspects of life are important characteristics of aging. Many such changes will affect the autonomy and well-being of older persons. At the start of LASA in 1991, in the Netherlands almost all research among older persons had been cross-sectional. This precludes the possibility to study the effects of changing circumstances on the autonomy and well-being of older persons. Moreover, processes of change in older persons are essentially multifactorial. To obtain proper insight into processes of change in older persons, multi- or preferably interdisciplinary research is a prerequisite. In the Netherlands, with some isolated exceptions, there is no tradition of such research.

Objectives
LASA is designed to be an interdisciplinary, longitudinal study. Although basically scientific in nature, the study should provide a basis for developing and evaluating (central and local government) policy in the field of aging. The global objective of current policy in the field of aging can be formulated as enhancing the autonomy and quality of life of older persons. It is expected that by using longitudinal data, policy relevant aspects of aging can be identified and new policy aims can be developed. Moreover, assumptions from which policy measures are developed can be tested, and effects of policy changes can be assessed prospectively. LASA is primarily an observational study; the database will allow testing of various specific hypotheses. Full intervention studies will not be included in LASA.

Central questions
LASA's main topics of concern are autonomy and quality of life of older persons. Autonomy is operationally defined as functioning, i.e. observable behavior; quality of life is defined as the evaluation by older persons of their functioning. Four components of functioning are distinguished: physical, cognitive, emotional and social. The four components will have different contributions to autonomy and quality of life. This distinction, however, does not intend to deny any interrelation between these components. The study focuses primarily on predictors of change in these components of functioning, on trajectories of functioning, and on consequences of change in functioning. The following central questions have been formulated:
1. Among older persons, what changes over time take place in the physical, cognitive, emotional and social components of functioning?
2. What are the predictors of change for each of the four components of functioning?
3. How are changes in the four components of functioning interrelated?
4. What are the consequences of changes in functioning in terms of older persons' contributions to society, their adjustment and their need for care?
More detailed research questions are formulated, some of which make use of additional data collected in specific subsamples. The most important of these side studies are on the course of depression, and on predictors of falls and fractures.

Elaboration
The measurement instruments selected largely correspond to those which are being used in potentially comparable research elsewhere in the Netherlands. Thus, a condition for wider use of the data is created, e.g. by pooling of data. Furthermore, a number of measurement instruments is selected for reasons of international comparability. This enables research on the effect of different socio-cultural developments and care systems on autonomy and well-being of older persons.
Changes in functioning are established during the study period, based on successive study cycles. In addition to interview questions, objective measurements provide indicators sensitive to change.
Physical functioning is measured by self-reports on functional limitations, and by objective measures of endurance, strength, mobility, coordination, balance, and vision. Cognitive functioning is measured by a brief screening test of dementia, and by tests of intelligence, learning capacity, memory, and information processing speed. Emotional functioning is measured by widely used depression and anxiety scales. Social functioning is measured by composition of the social network, frequency of contacts, exchange of support, and by social participation.
In addition to the behavioral aspect of functioning, the respondent's evaluation of their functioning is recorded, including self-perceptions of health, memory complaints, and loneliness.
Characteristics that are expected to predict changes in one of more of the components of functioning (the independent variables) are related both to the environment and to the individual: chronic conditions, use of medications, objective clinical assessments, use of services, life style, personality, personal biography, housing and living arrangements, socio-economic status, and "life events" prior to and during the study period.
Personal standards or aspiration levels and coping, expect to influence trajectories as mediating variables, are operationally defined as norms about aging, priorities in life, perceived self-efficacy, mastery, humor as a coping strategy, metamemory, and standards of affiliation.
The consequences of improvements and declines in functioning and the resulting (in)dependence are quantified in terms of the need for health and social services. Time, circumstances and causes of death are studied in connection with type of functional decline in the last phase of life.

The conceptual model described is summarized in the figure below.


Acknowledgement
The Longitudinal Aging Study Amsterdam is facilitated primarily by the Department of Policies for the Ageing, Ministry of Health, Welfare, and Sports, and by the Vrije Universiteit. Other grants are provided by the Prevention Fund / Health Research and Development Council (ZON), the University Stimulating Fund of the Vrije Universiteit, the National Research Program on the Chronically ill, and the Netherlands Organization for Scientific Research (NWO). The Vrije Universiteit supports the study by supplying several research staff, housing, and facilities.

Institutional affiliations within the Vrije Universiteit
LASA is carried out primarily at the Department of Psychiatry (Faculty of Medicine; Institute for Research in Extramural Medicine, EMGO), and at the Department of Sociology (Faculty of Social Sciences). Since 1995, also the Department of Endocrinology (VU Medical Center, as far as it resorts under EMGO), is responsible for the execution of LASA. Furthermore, collaboration has been effectuated with the Departments of General Practice, Nursing Home and Social Medicine (VU Medical Center, as far as it resorts under EMGO), the Department of Education Sciences (Faculty of Human Movement Sciences), the Department of Social Psychiatry (Faculty of Psychology and Education), and the Department of Econometrics (Faculty of Economics).

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Updated 16-4-2008
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