Racial, Ethnic, and Sex Disparities in Mental Health Among US Service Members and Veterans: Findings From the Millennium Cohort Study.

Although disparities in mental health occur within racially, ethnically, and sex-diverse civilian populations, it is unclear whether these disparities persist within US military populations. Using cross-sectional data from the Millennium Cohort Study (2014-2016; n = 103,184; 70.3% male; 75.7% non-Hispanic White), a series of logistic regression analyses were conducted to examine whether racial, ethnic, and/or sex disparities were found in mental health outcomes (posttraumatic stress disorder (PTSD), depression, anxiety, and problematic anger), hierarchically adjusting for sociodemographic, military, health-related, and social support factors. Compared with non-Hispanic White individuals, those who identified as American Indian/Alaska Native, non-Hispanic Black, Hispanic/Latino, or multiracial showed greater risk of PTSD, depression, anxiety, and problematic anger in unadjusted models. Racial and ethnic disparities in mental health were partially explained by health-related and social support factors. Women showed greater risk of depression and anxiety and lower risk of PTSD than men. Evidence of intersectionality emerged for problematic anger among Hispanic/Latino and Asian or Pacific Islander women. Overall, racial, ethnic, and sex disparities in mental health persisted among service members and veterans. Future research and interventions are recommended to reduce these disparities and improve the health and well-being of diverse service members and veterans.

Survey response over 15 years of follow-up in the Millennium Cohort Study.

BACKGROUND: Patterns of survey response and the characteristics associated with response over time in longitudinal studies are important to discern for the development of tailored retention efforts aimed at minimizing response bias. The Millennium Cohort Study, the largest and longest running cohort study of military personnel and veterans, is designed to examine the long-term health effects of military service and experiences and thus relies on continued participant survey responses over time. Here, we describe the response rates for follow-up survey data collected over 15 years and identify characteristics associated with follow-up survey response and mode of response (paper vs. web). METHOD: Patterns of follow-up survey response and response mode (web, paper, none) were examined among eligible participants (n=198,833), who were initially recruited in four panels from 2001 to 2013 in the Millennium Cohort Study, for a follow-up period of 3-15 years (2004-2016). Military and sociodemographic factors (i.e., enrollment panel, sex, birth year, race and ethnicity, educational attainment, marital status, service component, service branch, pay grade, military occupation, length of service, and time deployed), life experiences and health-related factors (i.e., military deployment/combat experience, life stressors, mental health, physical health, and unhealthy behaviors) were used to examine follow-up response and survey mode over time in multivariable generalized estimating equation models. RESULTS: Overall, an average response rate of 60% was observed across all follow-up waves. Factors associated with follow-up survey response over time included increased educational attainment, married status, female sex, older age, military deployment (regardless of combat experience), and higher number of life stressors, mental health issues, and physical health diagnoses. CONCLUSION: Despite the challenges associated with collecting multiple waves of follow-up survey data from members of the U.S. military during and after service, the Millennium Cohort Study has maintained a relatively robust response rate over time. The incorporation of tailored messages and outreach to those groups least likely to respond over time may improve retention and thereby increase the representativeness and generalizability of collected survey data.

Military service experiences and reasons for service separation among lesbian, gay, and bisexual individuals in a large military cohort.

BACKGROUND: The well-being of lesbian, gay, and bisexual (LGB) individuals is a topic of increasing concern within the military where significant institutional barriers, targeted aggression, and differential organizational policies such as "Don't Ask Don't Tell" have historically contributed to experiences of exclusion and discrimination. However, limited research has examined specific military and post-separation experiences among LGB service members and veterans. The goal of this study was to examine differences in military and service separation experiences by sexual orientation among a large representative sample of United States service members and veterans. METHODS: Survey data from the 2016 Millennium Cohort Study follow-up questionnaire were used to assess sexual orientation and multiple outcomes of interest: military experiences (morale, feelings about the military, missed workdays) and service separation experiences (reasons for separation, post-separation employment). The associations between sexual orientation (LGB versus heterosexual) and each of these outcomes were evaluated in a series of adjusted logistic regression models, stratified by sex when interactions were observed. RESULTS: Of the 99,599 participants, 3.4% identified as LGB. In adjusted models, LGB service members had significantly higher odds than heterosexual service members of feeling: unimpressed by the quality of unit leadership, unsupported by the military, and negative about the military overall. Bisexual women were more likely than heterosexual women to feel less unit camaraderie; both gay and bisexual men felt less camaraderie than heterosexual men. LGB veterans were more likely than heterosexual peers of the same sex to separate from service due to unplanned administrative reasons. Compared to heterosexual women, lesbian and bisexual women were more likely to separate from service due to dissatisfaction with promotions/pay and disability/medical reasons, while bisexual women specifically separated due to dissatisfaction with leadership and incompatibility with the military. Gay and bisexual men also reported separating due to incompatibility with the military, but only bisexual men were more likely to report separating due to disability/medical reasons compared to heterosexual men. CONCLUSIONS: Less positive military- and separation-specific experiences disproportionately affected LGB service members in this study. Promoting inclusion and increasing support for LGB service members may improve satisfaction with military service and retention.

Multiple imputation validation study: addressing unmeasured survey data in a longitudinal design.

BACKGROUND: Questionnaires used in longitudinal studies may have questions added or removed over time for numerous reasons. Data missing completely at a follow-up survey is a unique issue for longitudinal studies. While such excluded questions lack information at one follow-up survey, they are collected at other follow-up surveys, and covariances observed at other follow-up surveys may allow for the recovery of the missing data. This study utilized data from a large longitudinal cohort study to assess the efficiency and feasibility of using multiple imputation (MI) to recover this type of information. METHODS: Millennium Cohort Study participants completed the 9-item Patient Health Questionnaire (PHQ) depression module at 2 time points (2004, 2007). The suicidal ideation item in the module was set to missing for the 2007 assessment. Several single-level MI models using different sets of predictors and forms of suicidal ideation were used to compare self-reported values and imputed values for this item in 2007. Additionally, associations with sleep duration and smoking status, which are related constructs, were compared between self-reported and imputed values of suicidal ideation. RESULTS: Among 63,028 participants eligible for imputation analysis, 4.05% reported suicidal ideation on the 2007 survey. The imputation models successfully identified suicidal ideation, with a sensitivity ranging between 34 and 66% and a positive predictive value between 36 and 42%. Specificity remained above 96% and negative predictive value above 97% for all imputed models. Similar associations were found for all imputation models on related constructs, though the dichotomous suicidal ideation imputed from the model using only PHQ depression items yielded estimates that were closest with the self-reported associations for all adjusted analyses. CONCLUSIONS: Although sensitivity and positive predictive value were relatively low, applying MI techniques allowed for inclusion of an otherwise missing variable. Additionally, correlations with related constructs were estimated near self-reported values. Therefore, the other 8 depression items can be used to estimate suicidal ideation that was completely missing from a survey using MI. However, these imputed values should not be used to estimate population prevalence.

Single and repeated high-level blast, low-level blast, and new-onset self-reported health conditions in the U.S. Millennium Cohort Study: An exploratory investigation.

Introduction: Although previous research suggests that overpressure exposure from either high-level blast (HLB) or low-level blast (LLB) are harmful to health, to date no large-scale studies with representative samples of military personnel have utilized prospective designs and self-reported measures to examine the relationships between blast exposure and health conditions. To address these limitations, this analysis of data from the Millennium Cohort Study (MCS), the largest and longest running study of U.S. service members and veterans, examined (1) whether single or repeated HLB exposure is associated with self-reported diagnoses of illness and injury, (2) whether repeated HLB is associated with greater risk than single HLB, (3) potential adverse consequences of LLB exposure using military occupation as a proxy, and (4) the combined effects of single or repeated HLB and LLB exposure. Method: MCS participants who completed the 2011-2013 survey (N = 138,949) were classified as having been exposed to "no," "single," or "repeated" HLB exposure, and into low or high risk of exposure to LLB based on occupation. Participants self-reported diagnosis of 45 medical conditions; newly reported diagnoses were regressed on single and repeated (vs. no) HLB, occupational risk of LLB, and relevant interactions using logistic regression. Results: Single and repeated HLB were associated with new onset of 25 and 29 diagnoses, respectively; repeated HLB exposure was associated with greater risk than single HLB exposure for five diagnoses (e.g., PTSD, depression). Occupational risk of LLB was associated with 11 diagnoses (e.g., PTSD, significant hearing loss). Additionally, 14 significant interactions were detected across 11 diagnoses. Discussion: Findings suggest that overpressure exposure (including single HLB, repeated HLB, and occupational risk of LLB) may increase the risks of self-reporting clinical diagnoses of PTSD, hearing loss, chronic fatigue syndrome, neuropathy-caused reduced sensation in the hands and feet, depression, vision loss, sinusitis, reflux, and anemia. Furthermore, the combination of HLB and LLB exposure may be associated with greater risk of migraines, PTSD, and impaired fecundity. These findings provide further evidence of the potential adverse consequences associated with overpressure exposure and underscore the necessity of public health surveillance initiatives for blast exposure and/or safety recommendations for training and operational environments.

Health Disparities Among Lesbian, Gay, and Bisexual Service Members and Veterans.

INTRODUCTION: This study investigated whether health disparities exist among lesbian, gay, and bisexual individuals serving in the U.S. military by examining the associations of sexual orientation with mental, physical, and behavioral health among a population-based sample of service members and veterans. METHODS: Sexual orientation and health outcomes were self-reported on the 2016 Millennium Cohort Study follow-up questionnaire (N=96,930). Health outcomes were assessed across 3 domains: mental health (post-traumatic stress disorder, depression, anxiety, binge eating, problematic anger), physical health (multiple somatic symptoms, physical functioning, BMI), and behavioral health (smoking, problem and risky drinking, insomnia). Adjusted logistic regression models conducted between 2019 and 2022 estimated the associations between sexual orientation and each health outcome. RESULTS: Lesbian, gay, and bisexual individuals (3.6% of the sample) were more likely to screen positive for post-traumatic stress disorder, depression, anxiety, binge eating, problematic anger, multiple somatic symptoms, and insomnia than heterosexual individuals. Gay/lesbian and bisexual women reported more adverse health outcomes (overweight and obesity, smoking, problem/risky drinking) than heterosexual women. Gay and bisexual men reported some adverse health outcomes (e.g., smoking and problem drinking) but better physical health (e.g., less overweight/obesity) than heterosexual men. CONCLUSIONS: Lesbian, gay, and bisexual service members reported poorer mental, physical, and behavioral health than heterosexual peers, most notably among gay/lesbian women and bisexual individuals. Findings suggest that lesbian, gay, and bisexual service members experience health disparities, despite many having equal eligibility for health care, highlighting the need for improved equity initiatives that promote cultural responsiveness, acceptance, and approaches to support the healthcare needs of lesbian, gay, and bisexual military members.

Sexual Health Problems among Service Men: The Influence of Posttraumatic Stress Disorder.

Military operational stressors, such as combat exposure, may increase the risk of sexual health problems. This study examined factors associated with sexual health problems, and tested the mediating effect of probable posttraumatic stress disorder (PTSD) on the association between stressors (i.e., combat deployment and sexual assault) and sexual health problems among U.S. service men. Using multivariable logistic regression (n = 16,603) and Cox proportional hazards models (n = 15,330), we estimated the risk of self-reported sexual health difficulties and sexual dysfunction medical encounters, respectively. Mediation analyses examined the effect of probable PTSD as an intermediate factor between high combat deployment and sexual assault on sexual health problems. Approximately 9% endorsed sexual health difficulties and 8% had a sexual dysfunction. Risk factors for these sexual health problems included older age, lower education level, enlisted rank, disabling injury, certain medical conditions, and higher body mass index. Probable PTSD significantly mediated the associations between high combat with sexual health problems and sexual assault with sexual dysfunction. Additionally, high combat was directly associated with sexual health difficulties. These findings indicate a relationship between these stressors and sexual health problems which suggests that treatment options should be expanded, especially to include psychogenic sexual dysfunctions.

The bi-directional relationship between post-traumatic stress disorder and obstructive sleep apnea and/or insomnia in a large U.S. military cohort.

OBJECTIVES: Determine if a bi-directional relationship exists between the development of sleep disorders (obstructive sleep apnea [OSA] and/or insomnia) and existing post-traumatic stress disorder (PTSD), and vice versa; and examine military-related factors associated with these potential relationships. DESIGN: Longitudinal analyses of a prospective representative U.S. military cohort. PARTICIPANTS: Millennium Cohort Study responders in 2011-2013 (Time 1 [T1]) and 2014-2016 (Time 2 [T2]) without insomnia or OSA at T1 (N = 65,915) or without PTSD at T1 (N = 71,256). MEASUREMENTS: Provider-diagnosed OSA, self-reported items for insomnia, provider-diagnosed PTSD, and current PTSD symptoms were assessed at T1 and T2. Adjusted multivariable models identified military-related factors associated with new-onset PTSD in those with OSA and/or insomnia, and vice versa. RESULTS: Self-reported history of provider-diagnosed PTSD without current symptoms at T1 was associated with new-onset OSA only and comorbid OSA/insomnia at T2, while current PTSD symptoms and/or diagnosis was associated with new-onset insomnia only. OSA/insomnia at T1 was consistently associated with newly reported PTSD symptoms or diagnosis except that insomnia only was not associated with newly reported provider-diagnosed PTSD. Military-related risk factors significantly associated with the bi-directional relationship for new-onset PTSD or OSA/insomnia included prior deployment with higher combat exposure and recent separation from the military; being an officer was protective for both outcomes. CONCLUSIONS: In this large military cohort, findings suggest that PTSD and OSA and/or insomnia are bi-directionally predictive for their development, which was sometimes revealed by health care utilization. Relevant military-related risk factors should be considered in efforts to prevent or treat PTSD and/or sleep disorders.

The Millennium Cohort Study: The first 20 years of research dedicated to understanding the long-term health of US Service Members and Veterans.

PURPOSE: The Millennium Cohort Study, the US Department of Defense's largest and longest running study, was conceived in 1999 to investigate the effects of military service on service member health and well-being by prospectively following active duty, Reserve, and National Guard personnel from all branches during and following military service. In commemoration of the Study's 20th anniversary, this paper provides a summary of its methods, key findings, and future directions. METHODS: Recruitment and enrollment of the first 5 panels occurred between 2001 and 2021. After completing a baseline survey, participants are requested to complete follow-up surveys every 3-5 years. RESULTS: Study research projects are categorized into 3 core portfolio areas (psychological health, physical health, and health-related behaviors) and several cross-cutting areas and have culminated in more than 120 publications to date. For example, some key Study findings include that specific military service-related factors (e.g., experiencing combat, serving in certain occupational subgroups) were associated with adverse health-related outcomes and that unhealthy behaviors and mental health issues may increase following the transition from military service to veteran status. CONCLUSIONS: The Study will continue to foster stakeholder relationships such that research findings inform and guide policy initiatives and health promotion efforts.

Longitudinal associations of military-related factors on self-reported sleep among U.S. service members.

STUDY OBJECTIVES: Sleep loss is common in the military, which can negatively affect health and readiness; however, it is largely unknown how sleep varies over a military career. This study sought to examine the relationships between military-related factors and the new onset and reoccurrence of short sleep duration and insomnia symptoms. METHODS: Millennium Cohort Study data were used to track U.S. military service members over time to examine longitudinal changes in sleep. Outcomes were self-reported average sleep duration (categorized as ≤5 h, 6 h, or 7-9 h [recommended]) and/or insomnia symptoms (having trouble falling or staying asleep). Associations between military-related factors and the new onset and reoccurrence of these sleep characteristics were determined, after controlling for multiple health and behavioral factors. RESULTS: Military-related factors consistently associated with an increased risk for new onset and/or reoccurrence of short sleep duration and insomnia symptoms included active duty component, Army or Marine Corps service, combat deployment, and longer than average deployment lengths. Military officers and noncombat deployers had decreased risk for either sleep characteristic. Time-in-service and separation from the military were complex factors; they lowered risk for ≤5 h sleep but increased risk for insomnia symptoms. CONCLUSIONS: Various military-related factors contribute to risk of short sleep duration and/or insomnia symptoms over time, although some factors affect these sleep characteristics differently. Also, even when these sleep characteristics remit, some military personnel have an increased risk of reoccurrence. Efforts to improve sleep prioritization and implement interventions targeting at-risk military populations, behaviors, and other significant factors are warranted.

Prevalence and predictors of insomnia and sleep medication use in a large tri-service US military sample.

OBJECTIVE: The presence of insomnia in the general military population is not well known. This study aimed to determine the prevalence of probable clinical insomnia and identify factors leading to new-onset insomnia and/or sleep medication use in a large military population. DESIGN: Cross-sectional and longitudinal analyses of a prospective cohort study. PARTICIPANTS: A tri-service US military and veteran cohort (sample range 99,383-137,114). MEASUREMENTS: Participants were surveyed in 2013 (Time 1 [T1]) and 2016 (Time 2 [T2]) using the clinically validated Insomnia Severity Index. The prevalence of insomnia and sleep medication use was quantified at both times. Multivariable models identified military factors associated with new-onset insomnia and/or sleep medication use while adjusting for covariates. RESULTS: The prevalence of insomnia at T1 and T2 was 16.3% and 11.2%, respectively. New-onset insomnia at T2 was reported by 6.0% of participants screening negative at T1; risk factors included Army service, combat deployment experience, and separation from military service. The prevalence of sleep medication use at T1 and T2 was 23.1% and 25.1%, respectively. Sleep medication use at T2 was newly-reported by 17.1% of participants not reporting sleep medication use at T1; risk factors included number of deployments and having a healthcare occupation. CONCLUSIONS: The prevalence of probable clinical insomnia in this large general military population is within the range of previous reports in military and civilian populations. Certain military factors that predict new-onset insomnia and/or sleep medication use should be considered when designing and implementing sleep interventions in military populations.

Sexual health difficulties among service women: the influence of posttraumatic stress disorder.

Background Sexual health among service women remains understudied, yet is related to health and quality of life. This study examined if the associations between recent combat and sexual assault with sexual health difficulties were mediated by mental disorders and identified factors associated with sexual health difficulties among service women. Methods Data from two time points (2013 and 2016) of the Millennium Cohort Study, a large military cohort, were used. The outcome was self-reported sexual health difficulties. Mediation analyses examined probable posttraumatic stress disorder (PTSD) and major depressive disorder (MDD) as intermediate variables between recent combat and sexual assault with the sexual health difficulties. Multivariable logistic regression modeling was used to examine the association of demographic, military, historical mental health, life stressors, and physical health factors with sexual health difficulties. Results Of the 6,524 service women, 13.5% endorsed experiencing sexual health difficulties. Recent combat and sexual assault were significantly associated with sexual health difficulties. Probable PTSD mediated the associations of recent combat and sexual assault with sexual health difficulties; probable MDD did not mediate these relationships. Other significant factors associated with sexual health difficulties included enlisted rank, historical mental disorders, childhood trauma, and disabling injury. Limitations Use of self-reported data, outcome not assessed using a standardized measure and future studies may benefit from examining other mediators. Conclusion Our findings that combat and sexual assault may have negative effects on service women's sexual health suggest that treatment options and insurance coverage for sexual health problems should be expanded.

Hypertension in military veterans is associated with combat exposure and combat injury.

BACKGROUND: Although the long-term effects of combat injury are not well understood, there is emerging concern that exposure to combat environments and subsequent injury may increase the risk of hypertension through changes in inflammatory responses, psychological stress and mental health, and health behaviors. METHODS: Data from the Millennium Cohort Study and the Department of Defense Trauma Registry were used to identify combat-exposed and combat-injured participants. Incident hypertension diagnoses were ascertained from the Millennium Cohort survey. The associations between combat exposure/injury and hypertension risk was estimated using multivariable complementary log-log survival models. RESULTS: The final analysis sample consisted of 38 734 participants. Of these, 50.8% deployed but were not exposed to combat, 48.6% deployed and were exposed to combat, and 0.6% had combat injury. Overall prevalence of hypertension was 7.6%. Compared with participants who deployed but did not experience combat (mild exposure), elevated odds of hypertension were observed among those who experienced combat but not wounded (moderate exposure; AOR, 1.28; 95% CI, 1.19-1.38) and those wounded in combat (high exposure; AOR, 1.46; 95% CI, 1.07-2.00). Sleep duration of less than 4 h (AOR, 1.21; 95% CI, 1.03-1.43), sleep duration of 4-6 h (AOR, 1.16; 95% CI, 1.05-1.29), posttraumatic stress disorder (AOR, 1.54; 95% CI, 1.26-1.87), and overweight (AOR, 1.77; 95% CI, 1.61-1.95) and obese (AOR, 2.77; 95% CI, 2.45-3.12) status were also associated with higher odds of hypertension. CONCLUSION: Results support the hypotheses that combat exposure increases hypertension risk and that combat injury exacerbates this risk.