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In 2011-2014, the MIDUS Refresher study recruited a national probability sample of 3,577 adults, aged 25 to 74, designed to replenish the original MIDUS 1 baseline cohort and paralleling the five decadal age groups of the MIDUS 1 baseline survey [ICPSR 2760]. The MIDUS Refresher survey employed the same comprehensive assessments as those assembled on the existing MIDUS sample, but with additional questions about the effect of the economic recession of 2008-09.

The MIDUS Refresher collection is split into two datasets: Aggregate Data and Coded Text Data. The Coded Text Dataset provides coded responses to open-ended question items in the Aggregate Dataset. The survey data collection (Project 1) [MIDUS, ICPSR 2760] consisted of a 30-minute phone interview followed by two 50-page mailed self-administered questionnaires. Survey data were collected on demographic, psycho-social, and physical and mental health information. This new crosssectional MIDUS sample allows the examination of period effects on health (mental and physical) related to the economic recession by comparing the pre-recession MIDUS 1 sample with the post-recession MIDUS Refresher sample. A further objective of the MIDUS Refresher sample was to strengthen cross-project analyses in MIDUS by increasing the sample sizes available for testing hypotheses dealing with the interplay of key factors (e.g., socioeconomic status, gender, psychosocial factors, biological factors) in mid- and laterlife health. To that end, the MIDUS Refresher sample followed the same multi-disciplinary protocol established in the main MIDUS sample, in that after completing the survey protocol respondents were asked to complete a cognitive assessment by phone (Project 3) [MIDUS 3, ICPSR 36346] and later became eligible to participate in daily diary assessments (Project 2) [MIDUS 2, ICPSR 4652] biomarker assessments (Project 4) [MIDUS 2: Biomarker Project, ICPSR 29282] and neuroscience assessments (Project 5) [MIDUS 2: Neuroscience Project, ICPSR 28683].

The MIDUS Refresher was funded by the National Institute on Aging as two separate but related efforts: The MIDUS Refresher younger decades (MRY), was fielded in November, 2011, and recruited over 2,100 new participants aged 25 to 54; Funding was later added for the MIDUS Refresher older decades (MRO), which was fielded in June, 2013 and recruited over 1,400 new participants aged 55 to 74.

Demographic variables include age, sex, gender, race, religion, and marital status.

The Biomarker study is Project 4 of the Midlife in the United States (MIDUS) longitudinal study, a national survey of more than 7,000 Americans (aged 25 to 74) begun in 1994. The purpose of the larger study was to investigate the role of behavioral, psychological, and social factors in understanding age-related differences in physical and mental health. With support from the National Institute on Aging (NIA), a longitudinal follow-up of the original MIDUS samples [core sample (N = 3,487), metropolitan over-samples (N = 757), twins (N = 957 pairs), and siblings (N = 950)] was conducted in 2004-2006. Guiding hypotheses, at the most general level, were that behavioral and psychosocial factors are consequential for health (physical and mental). A description of the study and findings from it are available on the MIDUS website.

The Biomarker Project (Project 4) of MIDUS 2 contains data from 1,255 respondents. These respondents include two distinct subsamples, all of whom completed the Project 1 Survey: (1) longitudinal survey sample (n = 1,054) and (2) Milwaukee sample (n = 201). The Milwaukee group contained individuals who participated in the baseline MIDUS Milwaukee study, initiated in 2005. The purpose of the Biomarker Project (Project 4) was to add comprehensive biological assessments on a subsample of MIDUS respondents, thus facilitating analyses that integrate behavioral and psychosocial factors with biology. The broad aim is to identify biopsychosocial pathways that contribute to diverse health outcomes. A further theme is to investigate protective roles that behavioral and psychosocial factors have in delaying morbidity and mortality, or in fostering resilience and recovery from health challenges once they occur. The research was not disease-specific, given that psychosocial factors have relevance across multiple health endpoints.

Biomarker data collection was carried out at three General Clinical Research Centers (at UCLA, University of Wisconsin, and Georgetown University). The biomarkers reflect functioning of the hypothalamic-pituitary-adrenal axis, the autonomic nervous system, the immune system, cardiovascular system, musculoskeletal system, antioxidants, and metabolic processes. Our specimens (fasting blood draw, 12-hour urine, saliva) allow for assessment of multiple indicators within these major systems. The protocol also included assessments by clinicians or trained staff, including vital signs, morphology, functional capacities, bone densitometry, medication usage, and a physical exam. Project staff obtained indicators of heart-rate variability, beat to beat blood pressure, respiration, and salivary cortisol assessments during an experimental protocol that included both a cognitive and orthostatic challenge. Finally, to augment the self-reported data collected in Project 1, participants completed a medical history, self-administered questionnaire, and self-reported sleep assessments. For respondents at one site (UW-Madison), objective sleep assessments were also obtained with an Actiwatch(R) activity monitor.

In 2012-2013, the MIDUS Milwaukee Refresher study recruited a sample of 508 Milwaukee African American adults, aged 25 to 64, designed to replenish the Midlife Development in the United States (MIDUS 2): Milwaukee African American Sample, 2005-2006 (ICPSR 22840). This sample was also designed to increase the number of racial minorities included in the broader MIDUS study. The MIDUS Milwaukee Refresher survey employed the same assessments (demographic, psycho-social, and physical and mental health) as those assembled on the existing MIDUS sample, but with additional questions about the effect of the economic recession of 2008-09. A sample of African Americans from Milwaukee County, Wisconsin, was stratified by age, gender, and income.

Area probability sampling methods were used to identify potential respondents. Field interviewers screened households to determine if they contained any African American adults. There was additional screening to achieve an appropriate age/gender distribution in a manner similar to what was done for the original MIDUS sample (Midlife in the United States (MIDUS 1), 1995-1996 [ICPSR 2760]). Milwaukee respondents were interviewed in their homes using a 2.5-hour Computer Assisted Personal Interview (CAPI) protocol and afterwards asked to complete a self-administered questionnaire (SAQ). All measures paralleled those used in the larger MIDUS samples. In addition to successful completion of the survey, participants were asked to complete a cognitive assessment by phone. Some respondents were eligible to participate in additional MIDUS projects: daily diary assessments, biomarker assessments, and neuroscience assessments.

In 2005, 592 African Americans from Milwaukee were added to the MIDUS sample to examine health issues in minority populations (for more details, see Midlife in the United States (MIDUS 2): Milwaukee African American Sample [ICPSR #22840]). Respondents were interviewed in their homes using a Computer Assisted Personal Interview (CAPI) survey protocol and asked to complete and return a Self-Administered Questionnaire (SAQ). Afterwards these individuals were eligible for participation in the same research protocol as the national MIDUS 2 sample, including cognitive, daily stress, biomarker, and neuroscience projects.

With support from the National Institute on Aging, a second wave of survey data collection on the Milwaukee sample was begun in 2016. The survey consisted of a 2.5 hour CAPI interview followed by a 45-page mailed SAQ. CAPI survey data was collected for 389 individuals, realizing a 78 percent response rate, adjusted for mortality and other eligibility criteria. Data collection for this follow-up wave largely repeated baseline assessments, with additional questions in selected areas (e.g., economic recession experiences, childhood experience with race, etc.). Following successful completion of the CAPI and SAQ protocols, individuals were eligible for participation in cognitive, daily stress, biomarker, and neuroscience projects.

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.