Women veterans are the fastest growing segment of patients receiving care from the Department of Veterans Affairs (VA), and make up 7.5% of VA patients (Frayne et al., 2018Frayne S.M. Saecho F. Friedman S.A. Shaw J.G. Romodan Y. Berg E. Haskell S. Sourcebook: Women veterans in the Veterans Health Administration. Volume 4: Longitudinal trends in sociodemographics, utilization, health profile, and geographic distribution. Department of Veterans Affairs, Washington, DC2018Google Scholar). Although the field of women veterans' research has grown tremendously in the last 20 years (Danan et al., 2017Danan E.R. Krebs E.E. Ensrud K. Koeller E. MacDonald R. Velasquez T. Wilt T.J. An evidence map of the women veterans' health research literature (2008-2015).Journal of General Internal Medicine. 2017; 32: 1359-1376Crossref PubMed Scopus (41) Google Scholar), there remain few clinical trials or studies on chronic disease among women. One barrier to building the portfolio of such research is the small number of women veterans with any given disease or condition at any one VA facility. To develop a robust scientific understanding of the health care needs and treatments for women veterans, VA research dollars must be leveraged across multisite partnerships and veteran research organizations, teams, and investigators. To spur such a collaboration, the VA Office of Research and Development sponsored this supplement to Women's Health Issues. The VA Cooperative Studies Program (www.research.va.gov/programs/csp/) in collaboration with the VA Women's Health Research Network (www.hsrd.research.va.gov/for_researchers/womens_health/wh-research-network.pdf) coordinated the development of the supplement from conceptualization to publication. These groups represent key parts of the VA Office of Research and Development research spectrum that collaborate in pursuit of the larger goal of bridging evidence to improve veteran health and health care delivery. This supplement aims to stimulate interest in the exploration of sex- and gender-based differences within the broader veteran research community to inform and accelerate the growth of evidence-based care for women and men veterans. It also builds on an existing tradition of special journal issues dedicated to the health and health care of women veterans (Bastian et al., 2013Bastian L.A. Bosworth H.B. Washington D.L. Yano E.M. Setting the stage: Research to inform interventions, practice and policy to improve women veterans' health and health care.Journal of General Internal Medicine. 2013; 28: S491-S494Crossref PubMed Scopus (13) Google Scholar, Bastian et al., 2015Bastian L.A. Mattocks K.M. Rosen A.K. Hamilton A.B. Bean-Mayberry B. Sadler A.G. Yano E.M. Informing policy to deliver comprehensive care for women veterans.Medical Care. 2015; 53: S1-S4Crossref PubMed Scopus (3) Google Scholar, Bastian et al., 2016Bastian L.A. Hayes P.M. Haskell S.G. Atkins D. Reiber G.E. LaCroix A.Z. Yano E.M. Improving our understanding of health issues in older women veterans.Gerontologist. 2016; 56: S10-S13Crossref PubMed Scopus (6) Google Scholar, Washington and Horner, 2006Washington D.L. Horner R.D. The health and health care of women veterans: Perspectives, new insights, and future research directions.Journal of General Internal Medicine. 2006; 21: S3-S4Crossref Scopus (9) Google Scholar, Yano and Frayne, 2011Yano E.M. Frayne S.M. Health and health care of women veterans and women in the military: Research informing evidence-based practice and policy.Womens Health Issues. 2011; 21: S64-S66Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar). In response to a call for papers, we received many thought-provoking submissions exploring sex- and gender-based differences in a variety of clinical contexts. Presented here are 13 articles addressing five key areas of importance to veteran health and health care: health conditions and health behaviors, cohort studies, trauma, suicide, and methods. Here we provide an overview of the included topics in relation to current priorities for the VA. Key to understanding the needs of the growing women veteran population is an appreciation of their prevalent health conditions, symptomatology, and health behavior. This understanding is particularly pertinent because the demographics of women veterans are shifting, including an increasing average age (Frayne et al., 2018Frayne S.M. Saecho F. Friedman S.A. Shaw J.G. Romodan Y. Berg E. Haskell S. Sourcebook: Women veterans in the Veterans Health Administration. Volume 4: Longitudinal trends in sociodemographics, utilization, health profile, and geographic distribution. Department of Veterans Affairs, Washington, DC2018Google Scholar). Several articles in this supplement build our understanding of prevalent health issues among women veterans and how these differ from men's health concerns. Three articles dive deeper into specific areas of health and health behaviors with potential gender differences. First, Danan et al., 2019aDanan E.R. Sherman S.E. Clothier B. Burgess D.J. Pinsker E. Joseph A.M. Fu S.F. Smoking cessation among female and male veterans before and after a randomized trial of proactive outreach.Womens Health Issues. 2019; 29: S15-S23Scopus (5) Google Scholar examined gender differences in smoking cessation when exposed to a proactive treatment regimen versus usual care. They found that, compared with men, women were less satisfied with the process for obtaining smoking cessation medications. In their exploratory subgroup analysis by gender, they did not find gender-based differences in response to the intervention. Although this hypothesis-generating result warrants replication in future research, it also reminds us of the importance of disseminating findings of no gender differences in addition to highlighting areas where differences exist. Negative findings are informative for identifying when gender-specific services may not be needed. Second, Naylor et al., 2019Naylor J.C. Wagner H.R. Johnston C. Elbogen E.E. Brancu M. Marx C.E. Strauss J.L. Pain intensity and pain interference in male and female Iraq/Afghanistan-era veterans.Womens Health Issues. 2019; 29: S24-S31Abstract Full Text Full Text PDF PubMed Scopus (13) Google Scholar examined the experience of pain among Operation Iraqi Freedom/Operation Enduring Freedom/Operation New Dawn veterans. They found that women reported higher levels of pain than men, and that pain intensity explained gender differences in pain interference. Understanding how and why gender differences in pain exist will be critical as pain management and the safe prescribing of opioids in the VA continues to be a clinical priority and a growing area of research (www.research.va.gov/topics/pain.cfm). Finally, Breland et al., 2019Breland J.Y. Wong M.S. Frayne S.M. Hoggatt K.J. Steers W.N. Saecho F. Washington D.L. Obesity and health care experiences among women and men veterans.Womens Health Issues. 2019; 29: S32-S38Scopus (5) Google Scholar explored the relationship between obesity, a common health condition with a range of associated health risks, and experiences within the health care system using the VA Survey of Healthcare Experiences of Patients. Specifically, they looked at patients' ratings of providers by gender and obesity status to better understand the relationship between weight and patient satisfaction among men and women. Interestingly, both men and women who had higher body mass indexes were more likely to receive self-management services. However, only among men was greater body mass index associated with giving lower provider ratings. This work underscores that, as the VA seeks to improve veterans’ experience, researchers and providers must consider gender even in the context of non–gender-specific health conditions. In addition to investigations centered on a particular health condition or behavior, this supplement also features three cohort studies that examine gender differences in veteran health at the population level. Two articles describe cohorts of veterans who served during the first Gulf War Era (1990–1991). This era marks a rapid growth in women in the service, and women veterans who served in the first Gulf War now make up 56% of all living women veterans (“Women Veterans Report, 2017Women Veterans Report: The Past, Present and Future of Women Veterans. Department of Veterans Affairs, National Center for Veterans Analysis and Statistics, Washington, DC2017Google Scholar). Although a significant body of work has examined general health conditions and symptomatology prominent in the Gulf War Era population, few have examined these health issues by gender. Articles by Dursa et al., 2019Dursa E.K. Barth S.K. Porter B.W. Schniederman A.I. Health status of female and male Gulf War and Gulf Era veterans: A population based study.Womens Health Issues. 2019; 29: S39-S46Scopus (16) Google Scholar and Brown et al., 2019Brown M.C. Sims K.J. Gifford E. Goldstein K.M. Johnson M.R. Williams C. Provenzale D. Gender-based differences among 1990-91 Gulf War Era veterans: Demographics, lifestyle behaviors, and health conditions.Womens Health Issues. 2019; 29: S47-S55Scopus (16) Google Scholar fill this gap by exploring current health, health behaviors, and symptoms among aging Gulf War Era veterans, both VA users and nonusers. These articles represent two distinct cohorts: one is a follow-up survey of a cohort originally established in 1995 and the other is a newly developed biorepository cohort created between 2014 and 2016. Both include veterans who do and who do not receive care within the VA, yielding more generalizable information on Gulf War Era veteran health. Together, they provide an informative picture of the current health status of this population by identifying conditions that are more prevalent among women than men (e.g., migraines, eating disorders, and depression). A third article by Harrington et al., 2019Harrington K.M. Nguyen X.T. Song R.J. Hannagan K. Quaden R. Gagnon D.R. Whitbourne S.B. on behalf of the VA Million Veteran ProgramGender differences in demographic and health characteristics of the Million Veteran Program Cohort.Womens Health Issues. 2019; 29: S56-S66Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar describes the health characteristics of current enrollees in the Million Veterans Program (MVP) Cohort. The MVP is an ongoing, nation-wide Office of Research and Development study that was launched as a Cooperative Studies Program initiative to recruit 1 million veterans from all service eras to support research on how genes affect health. At the time of this writing, MVP has enrolled 750,000 veterans, 8.9% of whom are women. Harrington et al. found notable differences between women and men MVP participants. For example, women reported better overall health and were less likely to smoke or drink alcohol, but reported worse physical fitness. The authors also found gender differences in health care use. Specifically, women were more likely to receive a prescription from the VA and were more likely to receive a majority of their health care from the VA than men, but had fewer hospitalizations. In addition to providing a better population-level understanding of health among veterans, the cohorts described by Harrington et al. and Brown et al. are designed to be platforms for future research. Their descriptions provide needed context to support the inclusion of gender-based analyses by investigators seeking to access these data-rich cohorts. The VA has a longstanding history of innovation and expertise in the area of caring for patients with traumatic experiences. One particular type of trauma that has potential gender-based differences is military sexual trauma (MST). Three articles in this issue address different aspects of MST and gender-based trauma. First, Bovin et al., 2019Bovin M.J. Black S.K. Kleiman S.E. Brown M.E. Brown L.G. Street A.E. Marx B.P. The impact of assessment modality and demographic characteristics on endorsement of military sexual trauma.Womens Health Issues. 2019; 29: S67-S73Scopus (16) Google Scholar found that both men and women were more likely to report MST when screened in the context of a research study compared with clinical settings, where screening took place in response to a clinical reminder. This difference was greatest for men. Second, Combellick et al., 2019Combellick J.L. Dziura J. Portnoy G.A. Mattocks K.M. Brandt C.A. Haskell S.G. Trauma and sexual risk: Do men and women veterans differ?.Womens Health Issues. 2019; 29: S74-S82Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar examined the effect of prior MST and subsequent risky sexual behaviors and found no significant relationship. Rather, intimate partner violence and childhood sexual abuse were associated with risky sexual behavior only for women, whereas for men, binge drinking was associated with risky sexual behavior. Moving beyond past patient experiences with trauma, Dyer et al., 2019Dyer K.E. Potter S.J. Hamilton A.B. Luger T.M. Bergman A.E. Yano E.M. Klap R. Gender differences in veterans’ perceptions of harassment on VA grounds.Womens Health Issues. 2019; 29: S83-S93Scopus (19) Google Scholar explored current issues of traumatic experiences, specifically harassment, within the VA. From 15 discussion groups across four VA Health Care Systems, they found clear gender differences in the experience and understanding of harassment, particularly around the definition of inappropriate behavior and who is responsible for improving the culture. Together, these studies broaden the discussion on trauma and gender to include consideration of the current culture of recognition, management, and prevention of repeat or newly experienced trauma in the veteran population. Decreasing veteran suicide is a top priority for the VA (Office of Mental Health and Suicide Prevention, 2018Office of Mental Health and Suicide PreventionVA national suicide data report. Department of Veterans Affairs, 2018www.mentalhealth.va.gov/docs/data-sheets/2015/OMHSP_National_Suicide_Data_Report_2005-2015_06-14-18_508.pdfDate accessed: May 13, 2019Google Scholar). In the general population, male suicide attempts are more likely to be lethal, but women also attempt suicide at concerning rates. Within the veteran population, little is known about how suicidal behavior may differ for women and men. Two articles address this critical area. First, Ronzitti et al., 2019Ronzitti S. Loree A.M. Potenza M.N. Decker S.E. Wilson S.M. Abel E.A. Goulet J.L. Gender differences in suicide and self-directed violence risk among veterans with posttraumatic stress and substance use disorders.Womens Health Issues. 2019; 29: S94-S102Scopus (14) Google Scholar sought to elucidate gender differences in the risk of self-directed violence and suicidal behavior among veterans with post-traumatic stress disorder. They found that women were more likely to experience self-directed violence than men, but less likely to die by suicide. The presence of a comorbid substance use disorder also increased the risk of self-directed violence in both men and women. Second, Kumpula et al., 2019Kumpula M.J. Wagner H.R. Dedert E.A. Crowe C. Day K. Powell K. Kimbrel N. An evaluation of the effectiveness of evidence-based psychotherapies for depression to reduce suicidal ideation among male and female veterans.Womens Health Issues. 2019; 29: S103-S111PubMed Scopus (8) Google Scholar explored the effect of three different evidence-based treatments for depression on decreases in suicidal ideation. They found all three to be effective, especially among women. However, for men, some are more effective than others. Specifically, interpersonal psychotherapy and cognitive–behavioral therapy led to greater decreases in suicidal ideation relative to acceptance commitment therapy for depression. These findings, the authors suggest, provide support for efforts to tailor treatments not just for women, but also for men. The final area of work represented in this supplement focuses on methods for approaching the field of sex and gender differences in veteran health. First, Danan et al., 2019bDanan E.R. Ullman K. Klap R.S. Yano E.M. Krebs E.E. Evidence map: Reporting of results by sex or gender in randomized controlled trials with women veteran participants (2008-2018).Womens Health Issues. 2019; 29: S112-S120Scopus (4) Google Scholar built on a recent systematic review that mapped the evidence surrounding women veterans’ health. This additional work sought to compare randomized controlled trials that did and did not report sex/gender differences. Of the trials that included both men and women, only 25% reported sex/gender results. Reassuringly, they found that the proportion of trials reporting results by sex/gender increased from 2008–2014 to 2015–2018. The authors include key recommendations for improving the reporting of sex and gender findings to guide future investigations. Second, Goldstein et al., 2019Goldstein K.M. Duan-Porter W. Alkon A. Voils C.I. Hastings S.N. Enrollment and retention of men and women in health services research & development trials.Womens Health Issues. 2019; 29: S121-S130Scopus (5) Google Scholar examined recently conducted behavioral trials in one VA Health Services Research and Development Center of Innovation to describe participation by gender. Although only one of eight included trials made special efforts to include women, the majority of studies included women at or above the proportion affected by the target condition. The authors also note that, once contacted about study participation, women veterans are as likely as men to be willing to take part in research, if not more so. This finding is encouraging as the field pursues including women veterans at levels that could support sex- and gender-based analyses. Further, it points to the need to explore alternative sampling approaches and recruitment efforts that do not systematically exclude women. An illustration of efforts to over recruit women is provided by Harrington et al. (see Cohort Studies), who provide a description of their experiences trying to enhance inclusion of women in the MVP cohort. Overall, the articles in this supplement represent a wide range of data sources and methodologic approaches reflecting the breadth of the VA women's health research program. These articles take advantage of the multiple opportunities offered by the VA as a large, national health care system with a robust electronic medical record and multiple, well-established research entities. The included works stem from not only trials (Danan et al., 2019aDanan E.R. Sherman S.E. Clothier B. Burgess D.J. Pinsker E. Joseph A.M. Fu S.F. Smoking cessation among female and male veterans before and after a randomized trial of proactive outreach.Womens Health Issues. 2019; 29: S15-S23Scopus (5) Google Scholar) and cohort studies (Dursa et al., 2019Dursa E.K. Barth S.K. Porter B.W. Schniederman A.I. Health status of female and male Gulf War and Gulf Era veterans: A population based study.Womens Health Issues. 2019; 29: S39-S46Scopus (16) Google Scholar, Harrington et al., 2019Harrington K.M. Nguyen X.T. Song R.J. Hannagan K. Quaden R. Gagnon D.R. Whitbourne S.B. on behalf of the VA Million Veteran ProgramGender differences in demographic and health characteristics of the Million Veteran Program Cohort.Womens Health Issues. 2019; 29: S56-S66Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar, Naylor et al., 2019Naylor J.C. Wagner H.R. Johnston C. Elbogen E.E. Brancu M. Marx C.E. Strauss J.L. Pain intensity and pain interference in male and female Iraq/Afghanistan-era veterans.Womens Health Issues. 2019; 29: S24-S31Abstract Full Text Full Text PDF PubMed Scopus (13) Google Scholar; Brown et al., 2019Brown M.C. Sims K.J. Gifford E. Goldstein K.M. Johnson M.R. Williams C. Provenzale D. Gender-based differences among 1990-91 Gulf War Era veterans: Demographics, lifestyle behaviors, and health conditions.Womens Health Issues. 2019; 29: S47-S55Scopus (16) Google Scholar), but also clinical program evaluations (Kumpula et al., 2019Kumpula M.J. Wagner H.R. Dedert E.A. Crowe C. Day K. Powell K. Kimbrel N. An evaluation of the effectiveness of evidence-based psychotherapies for depression to reduce suicidal ideation among male and female veterans.Womens Health Issues. 2019; 29: S103-S111PubMed Scopus (8) Google Scholar), VA patient experience surveys (Breland et al., 2019Breland J.Y. Wong M.S. Frayne S.M. Hoggatt K.J. Steers W.N. Saecho F. Washington D.L. Obesity and health care experiences among women and men veterans.Womens Health Issues. 2019; 29: S32-S38Scopus (5) Google Scholar), and research process metrics (Goldstein et al., 2019Goldstein K.M. Duan-Porter W. Alkon A. Voils C.I. Hastings S.N. Enrollment and retention of men and women in health services research & development trials.Womens Health Issues. 2019; 29: S121-S130Scopus (5) Google Scholar). Multiple VA research entities are represented in this collection, including the Cooperative Studies Program (e.g., Harrington et al., 2019Harrington K.M. Nguyen X.T. Song R.J. Hannagan K. Quaden R. Gagnon D.R. Whitbourne S.B. on behalf of the VA Million Veteran ProgramGender differences in demographic and health characteristics of the Million Veteran Program Cohort.Womens Health Issues. 2019; 29: S56-S66Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar; Brown et al., 2019Brown M.C. Sims K.J. Gifford E. Goldstein K.M. Johnson M.R. Williams C. Provenzale D. Gender-based differences among 1990-91 Gulf War Era veterans: Demographics, lifestyle behaviors, and health conditions.Womens Health Issues. 2019; 29: S47-S55Scopus (16) Google Scholar), the VA Evidence Synthesis Program (Danan et al., 2019bDanan E.R. Ullman K. Klap R.S. Yano E.M. Krebs E.E. Evidence map: Reporting of results by sex or gender in randomized controlled trials with women veteran participants (2008-2018).Womens Health Issues. 2019; 29: S112-S120Scopus (4) Google Scholar), Health Services Research & Development (Combellick et al., 2019Combellick J.L. Dziura J. Portnoy G.A. Mattocks K.M. Brandt C.A. Haskell S.G. Trauma and sexual risk: Do men and women veterans differ?.Womens Health Issues. 2019; 29: S74-S82Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar; Danan et al., 2019aDanan E.R. Sherman S.E. Clothier B. Burgess D.J. Pinsker E. Joseph A.M. Fu S.F. Smoking cessation among female and male veterans before and after a randomized trial of proactive outreach.Womens Health Issues. 2019; 29: S15-S23Scopus (5) Google Scholar; Goldstein et al., 2019Goldstein K.M. Duan-Porter W. Alkon A. Voils C.I. Hastings S.N. Enrollment and retention of men and women in health services research & development trials.Womens Health Issues. 2019; 29: S121-S130Scopus (5) Google Scholar), and Mental Illness Research Education Clinical Centers of Excellence (Naylor et al., 2019Naylor J.C. Wagner H.R. Johnston C. Elbogen E.E. Brancu M. Marx C.E. Strauss J.L. Pain intensity and pain interference in male and female Iraq/Afghanistan-era veterans.Womens Health Issues. 2019; 29: S24-S31Abstract Full Text Full Text PDF PubMed Scopus (13) Google Scholar). Bovin et al. exemplify the usefulness of combining the VA's array of data sources, including electronic medical record and research survey data, to produce clinically important findings related to MST screening. Finally, the included articles use both qualitative (Dyer et al., 2019Dyer K.E. Potter S.J. Hamilton A.B. Luger T.M. Bergman A.E. Yano E.M. Klap R. Gender differences in veterans’ perceptions of harassment on VA grounds.Womens Health Issues. 2019; 29: S83-S93Scopus (19) Google Scholar) and quantitative approaches to address important questions about gender/sex differences. Together, this work demonstrates that the veteran research community is well-suited to contribute to our understanding of gender and sex differences. The VA's commitment to this pursuit is emphasized by the commentary by Huang and Ramoni, 2019Huang G. Ramoni R. Evidence-based care for women veterans: A burgeoning effort in the Department of Veterans Affairs Healthcare System.Womens Health Issues. 2019; 29: S6-S8Scopus (1) Google Scholar.