A retrospective cohort study of U.S. service members returning from Afghanistan and Iraq: is physical health worsening over time?

Prior to deployment to Afghanistan and Iraq in support of Operations Enduring and Iraqi Freedom (OEF/OIF), US service members report baseline health functioning superior to that of the general US population [1]. Following deployment, however, veterans report they have poorer health [2, 3]. In fact, the number of OEF/OIF veterans rating their overall health as fair or poor doubled six months after returning home as compared to their initial post-deployment assessment [2]. This is concerning because lower self-assessed functional health, particularly in the physical domain, has been associated with both greater health care utilization and mortality in veterans of prior conflicts [4‐6] and in community samples [7, 8].

Although several studies suggest that as time since deployment to OEF/OIF increases so too does the prevalence of poor mental health functioning among US service members, [2, 9, 10] less attention has been paid to how physical functioning changes over time [11‐13]. Importantly, we do not know whether there is a similar trend toward reduced physical function over time since return from deployment from OEF/OIF. Such investigation is especially warranted given that veterans of prior conflicts generally have worse health functioning than the general U.S. population, [5, 14] with the largest disparity observed in the physical domain [6]. Moreover, a worsening of physical functioning over time could lead to long term disability and have numerous public health implications (e.g., greater health care utilization and mortality) that would be especially problematic for this relatively young, working age population.

Therefore, the purpose of this study is to examine physical health in OEF/OIF veterans as a function of time since deployment using data from OEF/OIF veterans seen in a post-deployment health clinic. We also examined data from a military community sample as a comparison group to enhance generalizability. This sample participated in a longitudinal, prospective cohort study of OEF/OIF veterans who were followed from pre-deployment to one year after return from deployment. Because of the strong link between Posttraumatic Stress Disorder (PTSD) and health as well as its high prevalence among OEF/OIF veterans [15, 16], we included PTSD in our analysis predicting post-deployment health functioning. Additionally, using data from both clinical (i.e., treatment-seeking) and community samples afforded us the ability to address the concern that our findings were specific only to a treatment-seeking sample. Moreover, if we were to find similar effects across these two different samples, it would suggest a more generalizable impact of military service and thus better inform the public health community.

Veterans evaluated at our post-deployment health clinic endorsed physical health-related functioning that is substantially worse than that of the general US population (Figure 1) and indicative of impaired physical functioning irrespective of time post-deployment (Figure 2). However, for those in our clinical sample the longer after the return from deployment that the veteran attended the clinic, the worse his/her physical function. PCS scores remained low (i.e., poor physical function) even after accounting for comorbidity with probable PTSD, suggesting that physical health-related functioning may be an important problem regardless of PTSD status. Similarly, two subscales that comprise the PCS score (i.e., physical functioning and role-physical functioning) also indicated that the longer after return from deployment that Veterans were seen in our clinic, the lower their physical health even with adjustment for PTSD, age and gender. Together these findings suggest that given the average age of our sample (i.e., 32 years), it is critically important to plan carefully for what could be substantial, and long-term future health care needs for this cohort of veterans.

A potential limitation of the cross-sectional clinical sample is that PCS scores indicating poor physical function may simply mean that veterans wait to be seen at our post-deployment health clinic until they are sufficiently symptomatic. Since we do not have pre- or early post-deployment data on this clinical sample it is impossible to say if the service members have worsened over time, if their condition has always been poor, or if those who were seen further from their deployment date simply had a higher threshold for seeking care in the face of symptoms. However, the PCS scores in our military community sample of individuals deploying to OEF/OIF obtained before, immediately after and about one-year post-deployment also demonstrated a decrease in PCS scores over time with lower scores post-deployment than pre-deployment despite the fact that the latest post-deployment data was obtained only one year after return (Figure 1). Additionally, we could confirm that on average, this sample was physically healthier than the general US population before deploying. Although a decrease in PCS scores from pre-deployment to immediately post-deployment may be expected due to the physical rigors of the deployment, it is concerning that physical function not only did not improve by 1 year post-deployment, but continued to decline. In fact, PCS scores obtained at 1-year were significantly lower than those obtained immediately post-deployment. Because PCL scores were not available for all time points in this longitudinal sample, we did not control for PTSD in this analysis. Regardless of the factors that may be affecting physical health functioning, such as the presence of probable PTSD, when compared to pre-deployment, PCS scores of veterans one year after deployment were more than three points lower, a difference that in prior literature has been considered clinically significant [23]. Equally concerning is that from immediately afterdeployment to the one year follow-up, these individuals (mean age = 28 years) demonstrated an approximately 0.9 point decrease in PCS. Thus, even in a military community sample group of veterans over just the first year after return we observed a decrease in physical function from pre- to one-year post-deployment (i.e., over approximately 2 years) that appears to be declining at a faster rate than normal aging. For example, this magnitude of decline is equivalent to approximately half the decrease seen in population norms from the mid-thirties to mid-forties [23]. That a decline in physical health-related functioning is also present in a military community sample reinforces our observations in those veterans seeking treatment and illustrates a potential robust trend towards declining physical health in OEF/OIF veterans.

In our clinical sample, the longer the duration between return from deployment and their visit to our clinic, the worse the Veteran’s physical health. Irrespective of the length between return from deployment and visit to our clinic, their rating of physical health is worse than that of the general U.S. population (Figure 1). Moreover, veterans 4 Yr+ after a combat deployment report physical health that is worse than individuals with hypertension or liver disease, and their PCS scores begin to approach those of individuals with more severe chronic diseases (Figure 2) [23]. This is alarming given that PCS scores from over 77,000 service members in the Millennium Cohort Study exceeded the US general population norm (95% CI: 53.3 – 53.4) [1] as did the PCS scores from our longitudinal military community sample at pre-deployment (Figure 1). Further, previous work in veteran and non-veteran community samples, even for those who are middle aged (i.e., Miilunpalo et al. [8]), has found that decreases in physical function (PCS) are related to increased risk of both hospitalization and mortality. For example, in a sample of mostly older veterans, a 10-point decrease in PCS in veterans is associated with an age-adjusted 1.4 – 1.8 fold increased risk of hospitalization and a 2.0 – 2.6 fold increased risk of mortality [15, 30]. A decrement of 5 – 10 points significantly increased the risk of hospitalization (OR 1.13) and mortality (OR 1.14) [30]. Considering that we found decrements in PCS ranging from 0.9 (immediately post to one-year) in our longitudinal military community sample and 4.2 (1 Yr to 4 yr+) in our cross-sectional sample, it suggests that continued declines like this in these relatively young veterans could confer a future increased risk of hospitalization and mortality. These preliminary data highlight the need for further longitudinal work beyond one-year post-deployment to determine the extent and mechanisms underlying declines in physical function in veterans seeking and not seeking care.

A strength of this study was our ability to compare data from our cross-sectional clinical sample to data from a longitudinal study of community military personnel. We were however, not able to control for PTSD in the community sample. Additionally, we were limited by only having self-report data and not assessing factors contributing to poorer physical health post-deployment such as physical ailments or injuries of particular relevance to this cohort of veterans, e.g. respiratory-related illnesses and mild traumatic brain injury. Future studies should continue to explore factors that contribute to declining physical function after deployment.

In summary, our observed PCS scores in OEF/OIF veterans were lower with increasing time between return from deployment and the visit to our clinic. These data are important because poorer physical function has been associated with greater health care utilization and increased mortality in both veterans and civilians [6, 7]. Though poor physical health may be attributable to a variety of factors, these data should serve as a critical warning as these veterans are self-reporting poor physical health well beyond what is expected for their ages. This work highlights the need for thorough post-deployment screening and early intervention to minimize the decline in physical health and any associated increases in disability and health care utilization that may result if physical dysfunction is not addressed in a timely way for returning OEF/OIF veterans.