It is well-known that the prevalence of obstructive sleep apnea (OSA) has dramatically increased among active duty Service members over approximately the past decade (MSMR 2010). Typical correlates of OSA in the civilian world, such as age and BMI, are to some extent limited to a ceiling effect in Service members; that is, in general the active-duty population is young and those with a higher weight are more likely to be separated for fitness reasons. So it does not seem that these variables would explain the rise in OSA diagnoses in the military. Moreover, while greater awareness and treatment-seeking, particularly as part of a medical rating, may contribute to greater diagnoses, it does not seem likely to me that those factors alone would explain a nearly six-fold increase. Which of course leads to the question: what is contributing to the rise in OSA among Service members?
I have seen suggestions in the research literature and via anecdotes of a potentially fascinating relationship between OSA and trauma. No, I am not referring to trauma such as physical trauma or TBI (which has a clearly documented relationship with sleep apnea). I am referring to the kind of emotional trauma we often associate with PTSD. In other words, does trauma exposure or PTSD contribute to the development of OSA? Different research teams have reached different conclusions, so let’s take a look at evidence on both sides of the fence.
An early study of Veterans found that there was a significantly higher rate of PTSD in those diagnosed with OSA (11.9%) than in those without OSA (4.7%; Sharafkhaneh, 2005). Similarly, a systematic review that was just published (Gupta & Simpson, 2014) concluded after considering nearly 50 studies that “…there may be an increased prevalence of OSA in individuals with…post-traumatic stress disorder.” Interestingly, given that one of the hypotheses of PTSD development relates to limbic system dysregulation, a review on neurological function in OSA patients concluded “the majority of abnormal [neurological] signals have been observed in the central nuclei of the limbic system or in [related structures]” meaning that limbic system dysregulation may also be associated with OSA (Li et al, 2014).
On the other hand, a recent study by Mysliwiec et al (2013) found in a sample of over 700 Service members referred for a sleep study that there was no apparent difference in prevalence of PTSD among those with no diagnosis (10.2%), mild OSA (9.7%), and moderate-severe OSA (11.5%). Another smaller study of combat deployers in the Warrior Transition unit who were referred for a sleep study and diagnosed with OSA found no differences in the percentages of those with and without PTSD (Capaldi, Guerrero & Kilgore, 2011). It’s worth noting that a major difference between these studies and the earlier study cited that did find differential rates of PTSD in OSA (Sharafkhaneh, 2005), other than the time period, is looking at a Veteran vs an active-duty population. However, studies of Dutch Veterans by van Liempt and colleagues have also shown no differential rate of OSA in PTSD patients.
Perhaps one issue leading to the confusion is whether it is trauma per se or a full-blown PTSD diagnosis that is considered. A series of studies by Barry Krakow and his colleagues have shown a relationship between OSA and trauma (for example, exposure to crime and natural disasters) among those who have other sleep disorders, such as insomnia. Interestingly, a study of Iraqi immigrants found that less than 1% who emigrated before the 1991 Gulf War had OSA compared to a surprising 30.2% who emigrated during and after the war, when ostensibly a lot of trauma exposure could have been occurring (Arnetz et al, 2012). While it was found that there was a direct relationship between PTSD symptoms and OSA outside of the usual covariates, and an even larger direct relationship between major depressive symptoms and OSA, no data was provided on the amount of actual self-reported trauma exposure as opposed to symptomology (Arnetz et al).
There are certainly some other challenges in my opinion with the literature that has connected PTSD and OSA, including co-morbidities (particularly age, gender, other sleep disorders to include insomnia, and blast injury or TBI) and generalizability (only VA-enrolled vets, persons already seeking treatment, the issue of statistical vs. clinical significance, etc.). Of course, there are many factors that complicate coming to a consensus, such as how PTSD is assessed or defined (for example, does a mental health provider conduct a formal assessment, or does a survey simply include a PTSD screening tool? Are participants categorized as with or without a PTSD diagnosis or are symptoms suggestive of PTSD included as a continuous variable?) and the recent inclusion in DSM-5 of negative mood and cognition features that may overlap with depression comparison groups used in studies before the publication of DSM-5.
For years the questions in our field have often boiled down to this: is there a direct link between behavioral health and physical health? When I started reading the literature for this blog article, I was feeling pretty confident that I would find numerous well-controlled studies linking OSA development to PTSD. Instead, by the end of wading through articles, while I still believe there is a relationship between the two conditions, I’m not certain about the details. As we say with any relationship, correlation is not causation; that is, it is possible that trauma exposure could promote the development of OSA, or that a pre-existing vulnerability to OSA/undiagnosed OSA could lead to a maladaptive trauma response, or even that a third factor could contribute to both PTSD and OSA development, such as the above-mentioned limbic system dysregulation. I’d love to hear your take and any suggested readings in the comments below.
As a final thought, I think it would be enlightening to take a look at this potential relationship from the aspect of treatment impact direction, for example, does treating OSA improve PTSD symptoms, and/or does treating PTSD improve OSA symptoms? After working on this article, I definitely would want to read further before making a guess, so stay tuned-I promise to write up what I find!
Dr. Diana Dolan is an Evidence-Based Psychotherapy trainer with the Center For Deployment Psychology at USU.
Obstructive sleep apnea, active component, U.S. Armed Forces, January 2000-December 2009. MSMR 2010;17:8-11.
Arnetz, B.B., Templin, T., Saudi, W., & Jamil, H. (2012). Obstructive sleep apnea, post-traumatic stress disorder and health in immigrants. Psychosomatic Medicine, 74: 824-831.
Capaldi, V.F., Guerrero, M.L., & Killgore, W.D. (2011). Sleep disruptions among returning combat veterans from Iraq and Afghanistan. Military Medicine, 176(8): 879-88.
Gupta, M.A & Simpson, F. C. (2014). Obstructive sleep apnea and psychiatric disorders: A systematic review. Journal of Clinical Sleep Medicine. Epub ahead of print. http://www.aasmnet.org/jcsm/
Li, J., Li, M.X., Liu, S.N., Wang, J.H., Huang, M., Wang, M. & Wang, S. (2014) Is brain damage really involved in the pathogenesis of obstructive sleep apnea? Neuroreport 25(8): 593-595.
Mysliwiec, V., McGraw, L., Pierce, R., Smith, P, Trapp, B., & Roth, B.J. (2013) Sleep disorders and associated medical comorbidities in active duty military personnel. Sleep, 36 (2): 167-74.
Sharafkhaneh, A., Giray, N., Richarson, P., Young, T. & Hirshkowitz, M. (2005). Association of psychiatric disorders and sleep apnea in a large cohort. Sleep 28(11): 1405-1411.