Literature Review Approach
To conduct the literature review, we used the conceptual framework described below, which helped us identify the key questions and search terms that informed our decisions about whether to include or exclude studies. The three key questions were as follows:
1. What are the specific types of sleep problems and disorders prevalent in the post-deployment period?
2. What are the risk factors for post-deployment sleep problems (demographic/ military support, health, psychological, and behavioral factors)?
3. What are the consequences of sleep-related disorders, poor sleep quality, and insufficient sleep duration on physical health, mental health, fatigue, and operational readiness?
To locate articles for the literature review, we performed comprehensive Internet searches for studies published between 2001 and 2012, using a broad range of search terms, such as sleep disorders, nightmares, mental health, insomnia, military, and veterans. We selected these years to focus on sleep problems following contemporary military operations—mainly those affecting military servicemembers in conflicts since September 11, 2001 (OEF, OIF, and OND). Table B.1 in Appendix B offers a detailed description of our literature search methodology, including search terms, search engines, and inclusion and exclusion criteria.
Prevalence studies were primarily cross-sectional and included samples of general military personnel and servicemembers in clinical settings (e.g., those seeking treatment for sleep problems). Studies on risk factors, correlates, and consequences of sleep disturbances included both cross-sectional and longitudinal research with military samples. However, in reviewing the literature, we placed greater emphasis on the longitudinal findings, given that cross-sectional studies cannot address temporal ordering or the directionality of relationships (e.g., whether sleep increases the risk of adverse mental health outcomes or vice versa).
Much of the broad civilian research base on insomnia and other sleep problems, as well as the research highlighting the consequences of sleep problems or disorders, could theoretically apply to military populations. However, several unique issues, including operational factors and safety concerns, are particularly salient to sleep among military populations, and the civilian research may be less informative when it comes to these factors. However, there is a substantial research base on the prevalence and consequences of poor sleep among servicemembers—a research base that has grown considerably over the past 15 years. Both research bases can inform policies tailored to the unique needs of military populations; thus, we drew from research on both of these populations in our review. It is noteworthy that none of the studies reviewed directly compared civilian and servicemember samples. This precluded us from drawing meaningful inferences regarding the relative prevalence of sleep problems among servicemember and civilian populations. In addition to the literature reviewed, we also considered the unique perspectives of our key informants and working group participants, which are incorporated throughout the chapter as corroborating evidence to support findings in the literature. Finally, we also further evaluated the prevalence and problems of servicemembers by developing and administering a sleep survey through the Deployment Life Study servicemember cohort; that survey is described in greater detail in Chapter Three.
-  While our original search was conducted in late 2012 and included articles through December 2012, we consistently checked the literature using the same search strategies identified here every three months during the drafting of this report to stay up-to-date on new literature in the field. We revised the draft report as new literature was identified. This report includes literature published through February 2014.