Since its inception in 1992, the Health and Retirement Study (HRS) has provided an invaluable, long-term look at the complex interplay of health, work, and economic status of Americans age 51 and older. Over the years, the Study has been recognized for its high level of innovation and unique approaches within the social science research arena and has become the premier source of retirement data. In terms of budget, sample size, number of interview hours, and number of researchers involved, the HRS ranks among the largest and most ambitious social and behavioral studies ever undertaken. Rather than being a narrowly controlled investigation of the hypotheses of a small group of scientists, it provides a laboratory for many researchers to explore their theories.
Today, the HRS continues to evolve as data collection techniques expand and the resulting data are refined. In 2006, the HRS was funded for 6 more years, allowing the Study team to adopt several new directions. Some of the recent and future HRS initiatives are described below.
BIOMARKER DATA COLLECTION EXPANDS
In response to growing research interest in the relationship between physical health and other aspects of life, in 2006 the HRS began to gather additional direct measures of HRS participants' physical well-being. In the course of in-person interviews with participants, the researchers have begun to gather objective data about individuals' physical performance (such as grip strength, lung capacity, and walking ability) and blood pressure, and will collect fingerstick blood spot samples to assay for some common disease markers. They will also collect and store salivary DNA samples. These data will provide a foundation for novel studies of chronic disease, morbidity, disability, and, ultimately, mortality within the HRS study population.
COGNITIVE MEASURES STRENGTHENED
The HRS was one of the first national health surveys to measure cognitive health at the population level. The Aging, Demographics, and Memory Study (ADAMS), a recently added supplement to the HRS, is the first of its kind to conduct in-home assessments of dementia on a national scale with a nationally representative sample of older adults. Incorporating measures of memory and thinking skills in the HRS has permitted researchers to identify individuals with cognitive impairment and to study the impact of the impairment on their families. Beyond ADAMS, the HRS team has begun a major effort to strengthen its cognitive measures, developing new adaptive testing methods to assess a broader range of cognitive functions than in the past.
MORE PSYCHOSOCIAL MEASURES ADDED
The early waves of the HRS, while strong in areas such as the measurement of participants' economic status, were less robust in their measurement of psychosocial dimensions. Following a series of workshops and Data Monitoring Committee meetings, the HRS has begun to add a significant number of psychosocial measures to its face-to-face interviews with people over age 50. In 2004, adopting an innovation included in a sister study, the English Longitudinal Study of Ageing (ELSA), the HRS began using a "leave behind" self-administered questionnaire to gather expanded psychosocial data. Since then, the HRS has consulted widely with psychologists and sociologists on the design of an expanded psychosocial instrument that was administered in 2006. This work will continue on the versions for 2008 and beyond.
INTERNATIONAL STUDIES GROW
As described in the Introduction, the HRS has served as a model for other longitudinal, population-based studies of older adults' health and retirement in other nations. Several of these studies-ELSA; the Survey of Health, Ageing, and Retirement in Europe (SHARE); and the Mexican Health and Aging Study (MHAS)-are well-established. Their success has generated interest in extending these efforts to Israel and countries in Eastern Europe. Other nations-Ireland, Australia, South Korea, Japan, Thailand, and China-are also actively planning HRS or SHARE equivalents, and the task of coordinating these studies has become significant. The availability of comparable cross-national data presents opportunities for new research, such as the investigation of the impact of country-level pension and health system variation that were never before possible with single-country studies.
Perhaps even more important, the new international studies have become nodes around which researchers from a variety of disciplines and fields have clustered. Interaction of these study teams with counterparts in other countries has, in an amazingly brief amount of time, created a new and vibrant international research community that has benefited the HRS in a number of ways, including the development of new instruments and ways of thinking. Recently published research examining the health of U.S. and British populations (Banks et al. 2006) represents one example of the potential of the availability of comparable national data.
INTERDISCIPLINARY RESEARCH ADVANCES
The HRS has proved to be an effective crucible for initiating and promoting problem-focused research that cuts across multiple domains, such as economic status, health, physiology, neurology, and cognition. This outcome has resulted, in part, from the facts that the Study focuses on problems of concern to different disciplines and that it includes measures drawn from a variety of research realms.
In addition, the HRS has spawned interaction between laboratory research and field-based survey research-two fields that in the past have generally operated independently of one another. For the future, the HRS team expects to see even greater collaboration between these two very separate research worlds, as measures developed in labs move out into the field and labs interested in individual differences administer parts of the HRS questionnaire to subjects in experiments. Already, for example, HRS investigators and others are experimenting with Internet interviewing, an interview mode that is well-adapted to performing experiments.
SURVEY COORDINATION ENRICHES KNOWLEDGE BASE
A 1987 meeting and subsequent report on data needs for research on health and retirement economics catalyzed the HRS's initial development. Now, some 20 years later, the National Institute on Aging's Behavioral and Social Research Program has begun to look at the field's data needs more broadly. One approach to enrich understanding of the antecedents to retirement and factors affecting retirement decision making is to view the HRS as an integral part of a family of surveys that gather data about human development and aging. For example, connecting the HRS with other studies that begin at birth or at age 18 can provide insight into relevant developmental processes.
As evidenced by the rapidly growing number of publications, working papers, and dissertations that have tapped data gathered through the HRS and the growing use of the HRS by researchers, policymakers, and program planners, the HRS clearly has been a successful longitudinal endeavor. This is true largely because it has served as an essential means to understand the dynamics of the aging of both individuals and the U.S. population. The aging of the population and the retirement of the baby-boom generation are considered by many to be among the most transformative demographic changes ever experienced in this country. In the coming years, by observing the dynamics of retirement and health, and people's social and economic well-being following retirement, the HRS will continue to be a powerful research tool for tracking and understanding this major national social transformation.