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.

Behavioral health and sleep problems among US Army veterinarians and veterinary technicians participating in the Millennium Cohort Study.

OBJECTIVE: To determine the prevalences and relative odds of mental health problems, suicidal ideation, psychotropic medication use, problem drinking, trouble sleeping, and lack of social support among veterinarians and veterinary technicians, compared with other medical professionals, in the US Army. SAMPLE: 7,744 US Army personnel (957 officers [101 veterinarians and 856 physicians and dentists] and 6,787 enlisted personnel [334 veterinary technicians and 6,453 medics]) participating in the Millennium Cohort Study. PROCEDURES: Eligible participants completed ≥ 1 survey while serving as an Army veterinarian, veterinary technician, physician, general dentist, or medic. Analysis methods including multivariable logistic regression adjusted for covariates and stratified by pay grade were used to investigate associations between each health-care occupation and outcomes of interest. RESULTS: Veterinarians had higher reported prevalences of mental health problems, trouble sleeping, and lack of social support than did nontrauma physicians, trauma physicians, or dentists. On multivariable analysis, veterinarians had higher odds of mental health problems, trouble sleeping, and lack of social support, compared with physicians and dentists combined; odds for these outcomes were also higher for veterinarians, compared with various individual reference groups. Veterinary technicians had lower reported prevalence and lower odds of psychotropic medication use, compared with medics. CONCLUSIONS AND CLINICAL RELEVANCE: Further examination of Army policies and organizational structures related to veterinarians may be warranted, along with the development of policies and interventions designed to improve mental health, sleep quality, and social support among military veterinarians.

Longitudinal trajectories of comorbid PTSD and depression symptoms among U.S. service members and veterans.

BACKGROUND: Posttraumatic stress disorder (PTSD) often co-occurs with other psychiatric disorders, particularly major depressive disorder (MDD). The current study examined longitudinal trajectories of PTSD and MDD symptoms among service members and veterans with comorbid PTSD/MDD. METHODS: Eligible participants (n = 1704) for the Millennium Cohort Study included those who screened positive at baseline for both PTSD (PTSD Checklist-Civilian Version) and MDD (Patient Health Questionnaire). Between 2001 and 2016, participants completed a baseline assessment and up to 4 follow-up assessments approximately every 3 years. Mixture modeling simultaneously determined trajectories of comorbid PTSD and MDD symptoms. Multinomial regression determined factors associated with latent class membership. RESULTS: Four distinct classes (chronic, relapse, gradual recovery, and rapid recovery) described symptom trajectories of PTSD/MDD. Membership in the chronic class was associated with older age, service branch, deployment with combat, anxiety, physical assault, disabling injury/illness, bodily pain, high levels of somatic symptoms, and less social support. CONCLUSIONS: Comorbid PTSD/MDD symptoms tend to move in tandem, and, although the largest class remitted symptoms, almost 25% of participants reported chronic comorbid symptoms across all time points. Results highlight the need to assess comorbid conditions in the context of PTSD. Future research should further evaluate the chronicity of comorbid symptoms over time.