Impact of Operational Sleep Disruption on PTSD-Relevant Fear Learning Processes
Abstract
Comprehensive Overview of the Project: Posttraumatic stress disorder (PTSD) is common among Service members and military Veterans. One defining feature of PTSD is impairments in fear and fear inhibition processes. In PTSD, fear conditioning occurs where cues in the environment lead people to predict imminent threat or danger. Fear inhibition includes both fear extinction and safety learning. Fear extinction is the process of learning that previous "threat" cues are no longer dangerous so the person no longer responds to those cues with fear. Safety learning is the opposite of fear learning, where the individual learns that certain cues in the environment predict safety or absence of danger. It is believed that learning fear inhibition, as well as retaining that learning over time, is critical to preventing PTSD after trauma exposure and recovering from PTSD once it develops. Unfortunately, sleep problems, particularly interruptions in certain stages of sleep, such as rapid eye movement (REM) sleep (the stage of sleep in which we dream), have been shown to impair peoples ability to retain fear inhibition, possibly making it harder to recover from trauma. This disruption in fear inhibition is of great concern because sleep problems are one of the core features of PTSD and thus may be involved in the maintenance of PTSD symptoms. While past studies strongly suggest REM sleep is necessary for fear inhibition, no studies have looked specifically at the types of sleep disruption seen in military personnel at risk for PTSD. There are two factors likely to disrupt normal REM sleep in military populations: REM fragmentation and circadian misalignment. REM fragmentation (frequent interruptions in REM sleep) can occur either due to generally disrupted and inconsistent sleep patterns seen during training and deployment or from insomnia and nightmares typical in the immediate aftermath of trauma exposure. Circadian misalignment occurs when one attempts to sleep outside of one s biological night. This misalignment could occur due to frequent travel across time zones, initiation of missions within days of entering a new time zone, and/or as a result of frequent nocturnal missions or other shift work. These operational realities would be expected to impair fear inhibition processes. The primary goals of this study are (a) to determine if these two common ways that REM sleep becomes disrupted in military operations impair fear inhibition processes in ways consistent with impairments seen in PTSD; and (b) test if increasing REM sleep can prevent impaired fear inhibition in the face of circadian misalignment. We will test REM fragmentation (Aim 1) and circadian misalignment (Aim 2) methods of disrupting REM sleep. We predict each method will lead to decreased quantity and/or quality of REM sleep, and this REM disruption will, in turn, impair fear inhibition. Sixty (60) participants will take part in Aim 1 in the San Diego Veterans Affairs Hospital and 60 will take part in Aim 2 at Monash University. Each site is uniquely experienced and suited to carry out their specific aim. Central Critical Problem/Question To Be Addressed: No study yet has examined if REM sleep disruption, of the kinds experienced by military personnel, does indeed directly influence the fear extinction and safety signal learning impairments that put individuals at risk for developing PTSD and/or not fully benefiting from PTSD treatment. Nor are there studies testing countermeasures designed to reverse REM sleep disruption and prevent impaired fear inhibition. This body of work cannot be translated into the clinic without testing such countermeasures. Ultimate Applicability and Impact of the Research: The proposed study holds the promise of identifying sleep-related elements of the operational environment that increase the risk of development and maintenance of PTSD. This knowledge, in turn, will allow us to more effectively prevent and treat PTSD.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 29, 2018
- Source ID
- W81XWH1810762
Entities
People
- Sean P.A. Drummond
Organizations
- Monash University
- United States Army