The nature of military service has a unique impact on sleep. A study of US military personnel indicated that the rate of insomnia has increased dramatically since the start of Operation Enduring Freedom in 2001 [17]. The study population included all service members in the active component of the army, navy, air force, marine corps, or coast guard between 1 January 2000 and 31 December 2009. For study purposes, insomnia was defined as two or more ambulatory visits within 90 days of each other or a hospitalization including one of five different insomnia ICD-9 codes. The crude incident rate for insomnia was calculated by the number of cases per 10,000 person-years. From 2000 to 2009, the crude incidence rate of insomnia in the US military increased from 7 to 136 cases per 10,000. The incidence rates increased for all service branches, but the greatest increase by far was in the army (from 7 to 226 cases per 10,000). In addition, the evaluation of individual cases of insomnia from before to after deployment revealed that the incidence rates for insomnia increased more than 250% in the army. Interestingly, the incidence rate of insomnia between 2000 and 2009 was higher for military health-care occupations (12–205 per 100,000) as compared to combat military occupations (4–145 per 100,000). The primary limitation of this study is that it is based on ICD-9 codes from ambulatory visits or hospitalizations rather than population samples. Whether the overall rate of insomnia in the military population as a whole is different from the rate in civilian populations is not clear.

The 2008 Department of Defense Survey of Health Related Behaviors [18] of 28,546 army, navy, marine corps, air force, and coast guard personnel indicated that only one quarter (24%) reported sleeping 7 or more hours per night in the past 6 months. The Walter Reed Army Institute for Research recommends that military service members obtain 7–8 h of good quality sleep every 24-h period to sustain operational readiness [19]. According to these guidelines, 75% of the respondents to the Defense Survey of Health Related Behaviors are getting too few hours of sleep.

Data from the Millennium Cohort Study provides additional information on sleep in US military personnel [20]. A survey of 41,225 military personnel from all US branches of service, including the Reserve and National Guard, indicated that service members report sleeping an average of 6.5 h per night. However, between 20 and 30% of the study cohort reported trouble sleeping over the past month. The primary limitation of the sleep data from the Millennium Cohort Study is that sleep habits were measured using two questions from the Posttraumatic Stress Disorder Checklist – Civilian (PCL-C) and the one question from the Patient Health Questionnaire (PHQ ) related to anxiety. Potentially, Millennium participants may have answered thinking of their sleep in relation to PTSD and anxiety rather than their sleep in general.

During deployment , reports of sleep disturbance increase. One study evaluated 156 air force personnel deployed in 2001 to an undisclosed bare-base environment in support of Operation Enduring Freedom [6]. The results indicated that 74% reported their quality of sleep was significantly worse in the deployed environment, 40% had a sleep efficiency less than 85%, and 42% took longer than 30 min to fall asleep.

The Mental Health Advisory Team (MHAT) Reports V [21] and VI [22] do not specifically report sleep habits during deployment to Operation Enduring Freedom or Operation Iraqi Freedom, but they do report the use of sleeping medications. Nine percent of soldiers serving in Afghanistan reported using sleeping medications [21]. A similar number of soldiers serving in Iraq as part of maneuver units (8%) reported using sleeping medications. However, 14% of soldiers serving in support and sustainment units reported using sleeping medications [22]. This was a statistically significant difference, even after controlling for gender, rank, and time in theater. Support and sustainment units include medical personnel who were identified by the Armed Forces Health Surveillance Center [17] to have higher rates of insomnia as compared to combat occupations.

The Joint Mental Health Advisory Team 7 (J-MHAT 7) [4] specifically assessed reasons for sleep disruption in army soldiers and marines deployed to Afghanistan in 2010. One-third of soldiers (33%) and almost 40% of marines (38%) reported not getting enough sleep, a slight increase from previous reports (29% of soldiers in the 2009 MHAT VI report, 25% of marines in the 2006 MHAT IV report, and 22% of marines in the 2008 MHAT V report). Reasons cited for poor sleep were similar between the soldiers and marines and included poor sleep environment (33% soldiers and 47% marines), nighttime duties (30% soldiers and 47% marines), high operations tempo (17% soldiers and 27% marines), stress related to personal life (11% soldiers and 13% marines), stress related to combat (10% soldiers and 16% marines), and off-duty leisure such as video games and movies (4% soldiers and 5% marines). Eleven percent of the soldiers and 7% of the marines reported taking medications for sleep. They also reported heavy caffeine use, with 60% of the soldiers who reported taking sleeping medications also reporting that they consumed at least one energy drink per day. In contrast, only 43% of the soldiers who did not report taking sleeping medications reported consuming at least one energy drink per day. One of the recommendations from this report was to include sleep hygiene and discipline training as part of predeployment training and to identify small unit leaders to be responsible for ensuring opportunities for sleep unique to the unit location and circumstances.

Stressors documented during deployment that prompt behavioral health intervention include sleep disturbance [5]. Sleep disturbance was one of the top five stressors during deployment and was the principle “other” behavioral health diagnoses recorded in almost 30% of individuals receiving care the first half of 2008 [23].

Upon redeployment, sleep disturbance often continues. In an electronic record review of 1887 predominantly navy and marine personnel, 41% of those who had been deployed to Iraq or Afghanistan reported sleep problems as compared with 25% of those who had been deployed elsewhere [7]. However, like the Millennium Cohort Study, sleep was assessed using the navy’s Post-Deployment Health Assessment Test (PDHAT), which includes all the questions from the PTSD Checklist – Military. Similarly, in the Millennium Cohort Study, individuals who had been deployed reported decreased sleep duration as compared with individuals who had never been deployed [20]. Other variables significantly associated with trouble sleeping included female gender, lower reported general health, and reported mental health symptoms [20].

Findings from a study of 130 injured service members with extremity trauma sustained during service in Operation Enduring Freedom or Operation Iraqi Freedom indicated that 71% reported sleep disturbance three or more nights per week (S. Young-McCaughan, C. M. Miaskowski, M. O. Bingham, C. A. Vriend, A. Inman, J. Menetrez, unpublished data, 2011). Sleep disturbance was more prevalent than pain (average pain ≥5 and/or worst pain ≥7 reported by 55% of sample), depression (Center for Epidemiologic Studies Depression Scale ≥16 reported by 52% of the sample), anxiety (Spielberger Anxiety Scale ≥46 reported by 27% of the sample), and PTSD (PTSD Checklist – Military ≥50 reported by 19% of the sample) (Young-McCaughan et al. unpublished data 2011).

Repeated deployments have been a commonplace for conflicts in support of combat operations following 9/11 [24]. In one study [25], approximately 40% of the over 1.3 million service members who have ever been deployed had been deployed at least twice, 12% had been deployed at least three times, 4% had been deployed at least four times, and 1% had been deployed at least five times. This same report documented sleep disorders as one of the most common conditions to increase following second and third deployments.

Sleep disturbance often affects more than just the individual. In a study of 45 male Operation Enduring Freedom/Operation Iraqi Freedom veterans, reports of sleep problems predicted lower marital and relationship satisfaction [26]. Together, sleep disturbance and sexual problems predicted 29% of the variance in relationship satisfaction.

Sleep disturbance is consistently reported as most prevalent in service members with posttraumatic stress [27–29]. In one study of 2863 soldiers redeploying from service in Iraq [28], 71% of the 432 individuals reporting symptoms of PTSD on the Patient Health Questionnaire (PHQ ) also reported sleep disturbance. In contrast, of the 2180 individuals not reporting symptoms of PTSD, only 26% reported sleep disturbance. The specific type of sleep disturbance is not queried with the PHQ . The report by 26% of those without symptoms of PTSD of sleep disturbance is more than three times greater than that reported in a study of 21,244 Gulf War veterans [27]. In the Gulf War veterans, only 8% of 1605 otherwise healthy individuals reported sleep disturbance, but 64% of the 1096 individuals with PTSD reported sleep disturbance. The variability in reports of sleep disturbance could be related to the conflict (Gulf War or Operation Enduring Freedom/Operation Iraqi Freedom), military status (active duty or retired), and comorbid medical and psychiatric conditions, as well as the questionnaire used to elicit this information.

Several military programs have been developed to evaluate and treat sleep disorders in garrison and during deployments. Two in-garrison military studies indicated that insomnia can be successfully treated using cognitive behavior therapy delivered in a psychoeducational group format [30] as well as in an integrated behavioral health format in a primary care setting [31]. The Walter Reed Army Institute of Research (WRAIR) has developed a sleep management system to assess and address sleep issues before and during deployments [32]. The program, developed prior to the Iraq and Afghanistan conflicts, includes the following six elements: (1) actigraphy measurement of soldier sleep in garrison and in theater, (2) a mathematical model to predict an individual soldier’s cognitive readiness as a function of his or her sleep, (3) guidelines for the use of stimulants, (4) guidelines for behavioral strategies to promote sleep, (5) guidelines for pharmacological strategies to promote sleep, and (6) guidelines and tools for monitoring performance in real time in operational environments.

Resiliency is traditionally a term used in mechanical engineering to describe the physical property of a material to absorb energy and change shape and then return to the original shape or position, either immediately or over time. More recently, the concept has been applied to adaptive responses to psychological stress. There is a great deal of variability in the understanding of psychological resilience, both in civilian and military populations [33]. One definition of psychological resiliency is a “dynamic process encompassing positive adaptation within the context of significant adversity” [34].

Understanding and promoting resilience is of great importance to the US military as it seeks to mediate the psychological stress of the ongoing conflicts in Iraq and Afghanistan [35–37]. Yet relatively little is known of the mechanisms for resilience, factors that contribute to psychological resilience to adversity encountered as part of military duty, or means to promote resiliency in service members [33]. In a group of 328 US air force medical personnel deploying to Iraq, psychological resilience (as assessed with the Connor-Davidson Resilience Scale) was significantly correlated (P < 0.05) with low predeployment stress, positive military experiences, and positive affect [38]. Sleep was not assessed in this study. Conducting a secondary analysis using data collected from 1632 male and female veterans of Vietnam, King and his colleagues [39] identified social support and hardiness as two key factors contributing to postwar resilience and recovery. Again, sleep was not assessed.

Despite a rudimentary understanding of psychological resilience and the factors that support resilience, the American military has instituted a variety of programs to promote resilience for service members. In 2007, the Battlemind training system was mandated to all US army units [40]. Battlemind training focuses on ten combat skills taking a cognitive and skills-based approach to focus on safety, relationships, and common physical, social, and psychological reactions to combat [41]. In a randomized controlled trial comparing stress education to Battlemind debriefing to small group Battlemind training (18–45 individuals) to large group Battlemind training (126–225 individuals), small group Battlemind training participants with high combat exposure reported fewer posttraumatic stress symptoms and sleep problems as compared to the stress education group [41]. Now known as resilience training, the Battlemind program provides training and information targeting all phases of the soldier deployment cycle, life cycle, and support system and “offers strength-based, positive psychology tools to aid Soldiers, Leaders, and Families in their ability to grow and thrive in the face of challenges and bounce back from adversity” [42].

In 2009, the Chairman of the Joint Chiefs of Staff, Admiral Michael Mullen, commissioned the Consortium for Human and Military Performance (CHAMP), working with scientists and leaders from the Uniformed Services University of the Health Sciences (USU), Samueli Institute, and the Institute for Alternative Futures to develop a comprehensive framework of Total Force Fitness (TFF) to promote resilience [43, 44]. The program uses a mind-body framework with eight domains of total fitness including physical [45], psychological [46], behavioral and occupational [47], medical and environmental [48], nutritional [49], spiritual [50], social [51], and family [52]. This work, now signed by the Chairman of the Joint Chiefs of Staff into policy, has resulted in a renewed emphasis on promoting resilience for military individuals, families, and communities before, during, and after deployments. The army at Fort Hood, Texas, operationalized Total Force Fitness, establishing the first multimodal, integrative program dedicated to integrating the body, mind, and spirit to produce a balanced lifestyle. The program was described by the Fort Hood and III Corps Deputy Commanding General as representing “a fundamental shift in focus toward holistic well-being and resiliency” [53]. How Total Force Fitness will be further implemented across the services is now being discussed [43]. Sleep is addressed in the physical, psychological, behavioral and occupational, and medical and environmental domains as either a key component of fitness or as an indicator of poor functioning. Although the actual efficacy of this program in increasing resiliency is not known, a program evaluation of Total Force Fitness is proposed that includes the assessment of sleep patterns [54].

In 2011, the University of Pennsylvania program “Comprehensive Soldier Fitness ” was mandated across the US Army. The program consists of four components including online self-assessment, an online self-help training, training of master resilience trainers, and mandatory resilience training at every army leader school [35]. Cornum and her colleagues [55] acknowledged the challenge of sleep deprivation during deployment, but it is not apparent that promoting restful sleep is a component of the program. Multiple assessments of the program are ongoing [56].

Some research suggests that restful sleep is an essential ingredient for achieving and maintaining psychological resilience during military deployments. In a study testing the stress buffering effects of self-engagement in soldiers deployed to Bosnia as part of Operation Joint Guard (OJG), Britt and Bliese [57] found that hours of sleep accounted for 14% of the variance in psychological distress. Fewer sleep problems were considered a positive outcome in testing Battlemind training [41]. But, while a better and more comprehensive understanding of military resilience is emerging from current programs and ongoing research, only a few authors have deliberately considered sleep as a component of resilience [32, 41, 47, 55, 57].

From the previous reviews of sleep and resilience in military personnel, sleep can be conceptualized as a base physiological requirement for resiliency similar to how air, food, and water are conceptualized as base physiological requirements for the attainment of higher levels of functioning (e.g., safety, love and belonging, esteem, and self-actualization) in Maslow’s hierarchy of needs [58]. Animal laboratory research has documented death from total sleep deprivation in rodent models [59]. Although there are no reports of human death from sleep deprivation, it is thought to be a life-sustaining physiological requirement. The authors propose that the progressive requirements for military resiliency are physiological, psychological, knowledge and skills, and social support (see Fig. 5.1), with sleep being one of the basic physiological requirements for success at sequential tasks. Examples of research suggesting that these are essential elements for psychological resilience are presented below.