DOI: 10.3886/icpsr36530.v4
title: Survey of Midlife in Japan (MIDJA 2): Biomarker Project, 2013-2014
title: Version 4

description: In 2008, with funding from the National Institute on Aging (NIA), baseline survey data were collected from a probability sample of Japanese adults (N=1,027) aged 30 to 79 from the Tokyo metropolitan area, resulting in the Survey of Midlife in Japan (MIDJA) [ICPSR 30822]. In 2009-2010, biomarker data was obtained from a subset (n=382) of these cases (MIDJA Biomarker) [ICPSR 34969]. 
The survey and biomarker measures obtained, parallel those in a national longitudinal sample of Americans known as Midlife in the United States (MIDUS) [ICPSR 4652: MIDUS 2 and ICPSR 2760: MIDUS 1]. The central objective was to compare the Japanese sample (MIDJA) with the United States sample (MIDUS) to test hypotheses about the role of psychosocial factors in the health (broadly defined) of mid- and later-life adults in Japan and the United States 
In 2012, with additional support from NIA, a longitudinal follow-up of the MIDJA sample was conducted resulting in a second wave (N=657) of survey data (MIDJA 2) [ICPSR 36427].
This collection reflects data from 2013-2014, when a second wave of biomarker data was obtained from a sub-sample (n=328) of those who completed the MIDJA 2 survey. Among this group, about 75 percent (n=243) also completed the first wave of biomarker assessments. 
Participants traveled to a clinic on the University of Tokyo campus where biomarker data (vital signs, morphometric assessments, blood assays, and medication data) were obtained. Participants also provided daily saliva samples for cortisol assessment and completed a self-administered medical history questionnaire, as well as a time preference questionnaire.
The medical history questionnaire included assessments of conditions and symptoms, major health and life events, nutrition/diet, and additional psychosocial measures (anxiety, depression, relationship quality, control, etc.). 
The time preference questionnaire was used to collect respondents' opinions on management of money and assets given hypothetical scenarios.
 Demographic variables include age, gender, and marital status.
description: The overarching goal of the Midlife Health in Japan (MIDJA) study was to conduct a multidisciplinary study of health and well-being in a sample of middle- and older-aged Japanese adults. Another objective was to compare the Japanese sample (MIDJA) with the United States sample (MIDUS) to test the hypotheses regarding cultural differences in aging health and well-being as well as in how psychosocial factors are linked with biological factors known to influence profiles of disease and disability.
description: The initial, baseline data collection occurred in two phases. The first phase, survey data collection, was conducted by Central Research Services (CRS), a survey research firm based in Tokyo. Following the convention of social surveys in Japan, the "deliver-and-pick-up" method was used for data collection. Participants in the second phase, a subset of those completing the survey, completed biomarker and other assessments in a local clinic as well as at home (saliva samples, questionnaire). 
Funding for a longitudinal follow-up was obtained in February 2012. This second wave of data collection also occurred in two phases. The first phase, survey data collection, was conducted by Shin Joho Center, a survey research firm based in Tokyo. Consistent with the baseline data collection the "deliver-and-pick-up" convention was once again followed. Participants in the second phase, biomarker assessments, once again completed biomarker assessments in a local clinic as well as at home.
description: The data are not weighted and no weight variables are present in the dataset.
description: Response Rates: All respondents who completed the longitudinal Survey were invited to participate in the MIDJA 2 Biomarker follow-up. Thus, the sample includes individuals who completed the baseline biomarker assessments and those who did not. Consequently, two response rates are reported: 1) 50.8 percent for the overall MIDJA 2 Biomarker sample, and 2) 79.2 percent for those individuals who completed both the baseline and the longitudinal biomarker assessments. Reasons for nonresponse included: moved, address unknown, absent during time of survey, and deceased. Detailed information regarding the response rates for various aspects of the MIDJA data collection is located in the "MIDJA Study Summary."
description: Presence of Common Scales: Please see the "MIDJA 2 Biomarker Project Documentation of Scales and Constructed Variables" for complete information regarding the scales for the MIDJA data collection.
description: All respondents who completed the longitudinal MIDJA 2 Survey [ICPSR 36427] were eligible to participate in this longitudinal biomarker follow-up. MIDJA staff sent recruitment letters to all individuals who completed the longitudinal survey, then made follow-up phone calls to answer any questions and make arrangements for travel to a clinic located on the University of Tokyo campus, to participate in the biological assessments.

The sampling procedure for the baseline data collection was based on the official registry maintained at the municipal office of each of 23 wards within the city of Tokyo. All residents of Japan are registered at a single address where they choose to live. Drawing on this information, CRS used an age-stratified random sample scheme. Samples were drawn from each of the 23 wards in accordance with the population ratio within each age/gender category.
description: Datasets: 
DS0: Study-Level Files
DS1: MIDJA 2 Biomarker Data
DS2: MIDJA 2 Stacked Medications Data
description: Noninstitutionalized, Japanese-speaking adults, who completed the MIDJA 2 Longitudinal Survey in May - October 2012. Smallest Geographic Unit: none
description: mail questionnaire; on-site questionnaireThe data in this collection can be linked to MIDJA and MIDUS datasets using the linking variable MIDJA_IDS. The documents "Guide to Merging the MIDJA 2 Biomarker and MIDUS Data" and "MIDJA 2 Biomarker to MIDJA 1 and MIDUS Roadmap (SAQ-Clinic-Meds)" should be consulted when merging the data files.Additional information about the Survey of Midlife in Japan can be found at the MIDUS Web site.The title of this study was changed from Survey of Midlife Development in Japan (MIDJA 2): Biomarker Project, 2013-2014, to Survey of Midlife in Japan (MIDJA 2): Biomarker Project, 2013-2014, on May 9, 2017.