Shoji Shinkai, Taro Fukaya, Tatsuro Ishizaki, Yoh Murayama, Ryo Hirayama, Shohei Okamoto
Members (Other institutions):
Jersey Liang, Hiroko Akiyama, Ikuko Sugawara, Hiroshi Murayama, Hidehiro Sugisawa, Yoko Sugihara, Yoshimi Tsuda, Atsuhiro Yamada, Ken Harada, Michiko Naoi, Jim Raymo
Nationwide representative sample of older Japanese, Long-term longitudinal study, Aging, Health, Frailty, Social relationships, Socioeconomic disparities, Birth cohort, Older-old, Data archive
This project (JAHEAD: Japanese Aging and Health Dynamics) started as a collaboration between the Tokyo Metropolitan Institute of Gerontology and the University of Michigan in the late 1980s, and has been continued for over 30 years through the participation of researchers at the University of Tokyo and other institutions. The history of this long-term longitudinal study and a list of publications are available on the JAHEAD website.
The first wave of the survey was conducted in 1987 with older Japanese aged 60 and over who were randomly selected nationwide. Thereafter, they were followed up every 3-4 years until Wave 7 in 2006 with the addition of new participants, and Wave 8 was conducted in 2012. In Wave 8, we began to follow up a new panel (aged 60 and over) including baby boomers who were born after World War II (dankai-no sedai), in addition to the older panel. We conducted Wave 9 in 2017 and plan to conduct Wave 10 in 2020 or 2021.
JAHEAD survey data have the following characteristics: 1) nationwide representative sample of Japanese older adults, 2) rich information on various aspects of health and life in older age gained through face-to-face interviews (e.g., physical and mental health, family, friends and neighbors, employment, social participation, health behavior, use of medical/care services, financial status, etc.), 3) long-term longitudinal data with multiple waves, 4) sampling design that allows us to focus on the older-old (i.e., a large-scale sample aged 70 years and over was added in 1999), and 5) permits the comparison of multiple birth cohorts. With regard to 2), we collected objective physical performance data in Waves 8 and 9 in addition to the usual self-reported health status.
JAHEAD has three goals. First, we aim to clarify issues among Japanese older adults and publish the findings domestically and internationally based on analyses that make the best use of the data characteristics described above. Second, we will continue to collect longitudinal data while adding new cohorts, and also archive the data to promote the secondary analysis of existing data among many researchers, including those in the future. Third, we aim to contribute to gerontology by engaging in research to improve the quality of data on older adults. In order to achieve these goals, we will focus on the following four themes:
1. Changes in health and life and their related factors in old age
It is an important issue politically as well as academically to understand how physical, psychological, and social functioning change as people get older. We will examine not only ‘average’ trajectories, but also the various patterns of trajectories that are affected by individual attributes, such as socioeconomic status. Moreover, our focus will be on the differential impact of the factors on health and well-being by gender and age, and also differences across cohorts and time.
2. Prevalence of frailty in the representative sample of Japanese order adults and its individual and regional differences
Although frailty of older adults has been studied in various local areas by many researchers, the criteria for evaluating frailty varied across studies and none of the studies were based on a nationwide representative sample in Japan. In JAHEAD, we will set the criteria using both self-reported data and physical measurements (grip strength, usual walking speed (2.5 m), height, weight), and clarify the individual and reginal prevalence of frailty as well as the nationwide total prevalence.
3. Development of research methods for studying older adults
(1) Home-visit physical measurements
Physical performance, such as grip strength and walking speed, is usually measured by professionals in public places where older adults have been invited for health check-ups. Considering the rapid increase in the number of oldest-old in Japan, it is necessary to develop a method to cover a wider range of people, including those who can not visit such public places by themselves.
JAHEAD physical measurements were introduced in Wave 8 using those of the Health and Retirement Study in the United States as a reference, after several trials to adjust them for use in Japan. Much effort was required to assure the participants’ safety and the reliability of the measurements because more than 200 interviewers had to perform them under various conditions in the participants’ homes. We will show the guidelines to share our experiences with other researchers.
(2) Regional-level environmental data
Regional characteristics, which are diverse even within Japan, may affect the health and life of older adults. Thus, we will perform multi-level analyses considering both person-level and reginal-level attributes. As regional-level attributes, census data and interviewers’ evaluations of the neighborhood environment are expected to be used.
4. Archiving data and promotion of secondary analysis
We have deposited the anonymous microdata in the University of Tokyo’s SSJDA (Social Science Japan Data Archive), which is the largest archive of social science data in Japan. Waves 1-7 (1987-2006) are already open to researchers other than JAHEAD members as the National Survey of the Japanese Elderly. By archiving data, we can keep valuable data safe and also contribute to academic research by providing opportunities for secondary analysis by young researchers. We are increasing our efforts to facilitate the secondary analysis in such ways as holding workshops.