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The Midlife in the United States (MIDUS) is a collaborative, interdisciplinary investigation of patterns, predictors, and consequences of midlife development in the areas of physical health, psychological well-being, and social responsibility. A description of the study and findings from it are available at http://www.midus.wisc.edu.

The first wave of the MIDUS study (MIDUS 1 or M1) collected survey data from a total of 7,108 participants. The baseline sample was comprised of individuals from four subsamples: (1) a national RDD (random digit dialing) sample (n=3,487); (2) oversamples from five metropolitan areas in the U.S. (n=757); (3) siblings of individuals from the RDD sample (n=950); and (4) a national RDD sample of twin pairs (n=1,914). All eligible participants were non-institutionalized, English-speaking adults in the coterminous United States, aged 25 to 74.

Data from the samples were collected primarily in 1995/96. The survey (Project 1) dataset contains responses from a 30-minute Phone interview and two 50-page Self-Administered Questionnaire (SAQ) instruments. Of the 7,108 respondents who completed the Phone interview, 6,325 also completed the SAQ.

This updated version of the study is comprised of three primary datasets:

Dataset 1, Main, Siblings, and Twin Data, contains responses from the main survey of 7,108 respondents. Respondents were asked to provide extensive information on their physical and mental health throughout their adult lives, and to assess the ways in which their lifestyles, including relationships and work-related demands, contributed to the conditions experienced. Those queried were asked to describe their histories of physical ailments, including heart-related conditions and cancer, as well as the treatment and/or lifestyle changes they went through as a result. A series of questions addressed alcohol, tobacco, and illegal drug use, and focused on history of use, regularity of use, attempts to quit, and how the use of those substances affected respondents' physical and mental well-being. Additional questions addressed respondents' sense of control over their health, their awareness of changes in their medical conditions, commitment to regular exercise and a healthy diet, experience with menopause, the decision-making process used to deal with health concerns, experiences with nontraditional remedies or therapies, and history of attending support groups. Respondents were asked to compare their overall well-being with that of their peers and to describe social, physical, and emotional characteristics typical of adults in their 20's, 40's, and 60's. Information on the work histories of respondents and their significant others was also elicited, with items covering the nature of their occupations, work-related physical and emotional demands, and how their personal health had correlated to their jobs. An additional series of questions focusing on childhood queried respondents regarding the presence/absence of their parents, religion, rules/punishments, love/affection, physical/verbal abuse, and the quality of their relationships with their parents and siblings. Respondents were also asked to consider their personal feelings of accomplishment, desire to learn, sense of control over their lives, interests, and hopes for the future.

The Datasets previously numbered 2 and 3 have been removed to avoid redundancies, and all datasets have been renumbered. Please refer to the readme file.

Dataset 2, Twin Screener Data, provides the first national sample of twin pairs ascertained randomly via the telephone.

Dataset 3, Coded Text Responses, describes how open-ended textual responses in the MIDUS 1 Computer-Assisted Telephone Interview (CATI) and Self-Administered Questionnaire (SAQ) were transformed into categorical numeric codes. These codes are included in a stand-alone dataset containing only those cases (N=3,950) that contained text data in their responses.

Online Analysis Only: Datasets 1, 2, and 3 were merged together by the SU_ID variable to form "Merged Data with Weights (Online Analysis Only)" (Dataset 4) for online analysis capabilities.

MIDUS also maintains a Colectica portal, which allows users to interact with variables across waves and create customized subsets. Registration is required.

In 1995-1996, the MacArthur Midlife Research Network carried out a national survey of 7,108 Americans aged 25 to 74 (MIDLIFE IN THE UNITED STATES (MIDUS), 1995-1996 [ICPSR 2760]). The purpose of the study was to investigate the role of behavioral, psychological, and social factors in understanding age-related differences in physical and mental health. The study was innovative for its broad scientific scope, its diverse samples (which included twins and the siblings of main sample respondents), and its creative use of in-depth assessments in key areas (e.g., daily stress and cognitive functioning). A description of the study and findings from it are available at http://www.midus.wisc.edu. With support from the National Institute on Aging, a longitudinal follow-up of the original MIDUS samples: core sample (N = 3,487), metropolitan over-samples (N = 757), twins (N = 925 complete pairs), and siblings (N = 950), was conducted in 2004-2006. Guiding hypotheses for it, at the most general level, were that behavioral and psychosocial factors are consequential for physical and mental health. MIDUS 2 respondents were aged 35 to 86. Data collection largely repeated baseline assessments (e.g., phone interview and extensive self-administered questionnaire), with additional questions in selected areas (e.g., cognitive functioning, optimism and coping, stressful life events, and caregiving). To add refinements to MIDUS 2, an African American sample (N = 592) was recruited from Milwaukee, Wisconsin, who participated in a personal interview and completed a questionnaire paralleling the above assessments. Survey data for the Milwaukee sample are available in a separate project [ICPSR 22840]. Also administered was a modified form of the mail questionnaire, via telephone, to respondents who did not complete a self-administered questionnaire.

In 1995-1996, the MacArthur Midlife Research Network carried out a national survey of over 7,000 Americans aged 25 to 74 [ICPSR 2760]. The purpose of the study was to investigate the role of behavioral, psychological, and social factors in understanding age-related differences in physical and mental health. The study was innovative for its broad scientific scope, its diverse samples (which included siblings of the main sample respondents and a national sample of twin pairs), and its creative use of in-depth assessments in key areas (e.g. daily diary of stressful experiences [ICPSR 3725] and cognitive functioning [ICPSR 3596]) on a subset of participants. A detailed description of the study and findings generated by it are available at: http://www.midus.wisc.edu

With support from the National Institute on Aging, a follow-up of the original Midlife Development in the United States (MIDUS) sample was conducted in 2004 (MIDUS 2 [ICPSR 4652]). The daily stress and cognitive functioning projects were repeated and expanded at MIDUS 2; in addition the protocol was expanded to include biomarkers and neuroscience.

In 2013 a third wave (MIDUS 3) of survey data was collected on longitudinal participants. Data collection for this follow-up wave largely repeated baseline assessments (e.g., phone interview and extensive self-administered questionnaire), with additional questions in selected areas such as economic recession experiences. Cognitive functioning data were also collected at the same time, while data collection for the daily diary, biomarker, and neuroscience projects commenced in 2017.

MIDUS also maintains a Colectica portal, which allows users to interact with variables across waves and create customized subsets. Registration is required.

In 2008, with funding from the National Institute on Aging (NIA), baseline survey data for the Survey of Midlife in Japan (MIDJA), April-September 2008 were collected from a probability sample of Japanese adults (N=1,027) aged 30 to 79 from the Tokyo metropolitan area (ICPSR 30822). In 2009-2010 biomarker data was obtained from a subset of these cases (ICPSR 34969).

The survey and biomarker measures obtained parallel those in a national longitudinal sample of Americans known as Midlife in the United States or MIDUS (ICPSR 2760: MIDUS 1 and ICPSR 4652: MIDUS 2). 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 completed. The data collection for this second wave (N=657) largely repeated the baseline assessments. The goal of the follow-up wave was to conduct comparisons of longitudinal data available from the Japanese sample (MIDJA) and the United States sample (MIDUS) to test the hypothesis about the role of psychosocial factors in predicting health changes (including biomarkers) in both cultural contexts. Cultural influences on age differences in health and well-being were also of interest.

Demographic and background information included gender, age, education, marital status, household composition, and income.

The Wisconsin Longitudinal Study (WLS) is a long-term study of a random sample of 10,317 men and women who graduated from Wisconsin high schools in 1957. The WLS provides an opportunity to study the life course, intergenerational transfers and relationships, family functioning, physical and mental health and well-being, and morbidity and mortality from late adolescence through 2025. WLS data also cover social background, youthful aspirations, schooling, military service, labor market experiences, family characteristics and events, social participation, psychological characteristics and retirement.

Survey data were collected from the original respondents (the graduates) in 1957, 1964, 1975, 1992, 2004, 2011, 2020 and 2022; from their parents in 1957 and 1964; from a selected sibling in 1977, 1994, 2005, 2011, 2020 and 2022; from the spouse of the original respondent in 2004; and from the spouse of the selected sibling in 2006.

The collection of cognitive function data among graduates and siblings under the ILIAD study (MPIS: Sanjay Asthana, Michal Engelman, and Pamela Herd) began in 2020 to measure risk and resilience of Alzheimer's disease and related dementia (ADRD) as the cohort reaches their 80s. Data from 2020 and 2022 have been released, and 2025 and 2027 wave releases are forthcoming.

The WLS also has extensive administrative linkages, including with the 1940 and 1950 census, Social Security records, voting participation, and Medicare claims data.