INTRODUCTION

Chronic pain is a major public health problem affecting approximately 100 million Americans1 and U.S. military veterans who are a particularly vulnerable group:2 up to 50% of male veterans3 and 78% of female veterans4 presenting to VHA primary care settings report chronic pain. Pain is one of the most common presenting complaints of Operation Enduring Freedom/Operation Iraqi Freedom/Operation New Dawn (OEF/OIF/OND) veterans treated in the Veterans Health Administration (VHA).5 Veterans from this era have higher rates of pain than non-veterans of similar ages, than veterans from other eras, and than a representative sample of U.S. adults.2, 5,6,7,–8

Citing efforts to improve pain management and address the opioid crisis, the Department of Veterans Affairs and Department of Defense (VA/DoD) Clinical Practice Guideline,9 Centers for Disease Control (CDC) Guideline for Prescribing Opioids for Chronic Pain,10, and National Pain Strategy (NPS)11 have highlighted the importance of multimodal treatment for chronic pain including non-opioid pain medication and non-pharmacological modalities (NPMs). The recent VHA State-Of-The-Art (SOTA) Conference, “Non-pharmacological approaches to chronic musculoskeletal pain management,” identified a range of NPMs as having sufficient evidence of effectiveness to encourage their routine availability in VHA. The SOTA Conference12 also categorized NPMs into three groups: psychological/behavioral (cognitive-behavioral therapy, acceptance and commitment therapy, mindfulness-based stress reduction), exercise/movement (physical therapy, structured exercise, tai chi, yoga), and manual (acupuncture, chiropractic/spinal manipulation, massage; which could also be categorized as passive approaches) therapies.12

Despite guidance recommending a multimodal approach, along with substantial evidence for the effectiveness of some NPMs,13,14,15,16,17,18,19,–20 over the past decade, opioid medications have often been used as a primary treatment modality for chronic pain.9 As opioids have been linked to numerous serious harms and demonstrated modest or no benefit, 21 increasing NPM uptake is a major emphasis of guidelines promoting reduced reliance on opioids for chronic pain.10 Understanding how to promote NPMs is important, yet little research regarding the NPM utilization has been conducted.

Studies have reported differences in NPM utilization for pain management by demographics, using survey data, electronic health records (EHR) data, and claims data.22,23,–24 Regarding psychological/behavioral therapies, one study using EHR data reported that female veterans receiving opioids for chronic pain were more likely to receive mental health assessments and psychotherapy than male veterans.22 Vignette studies found that when a patient with chronic pain was described as female or reporting depression, providers were more likely to suggest a referral to mental health.25, 26 The 2011 Institute of Medicine report, Relieving Pain in America, noted that women with pain are at greater risk of sub-optimal patient-provider communication and stigma regarding pain; stereotypes or the perception that women’s pain is more psychological may contribute to this finding.1

Concerning exercise/movement therapies, one study of persons with low back pain (acute or chronic) found that participants using opioids were less likely to engage in physical therapy, but found no differences by sex, age, non-opioid pain medication use, or mental health diagnoses.23 Another study using VHA EHR data reported female (versus male) veterans prescribed long-term opioids were more likely to receive rehabilitation therapies;22 another study of post-deployment veterans with pain reported higher pain severity, absence of a mental health diagnosis, and number of pain conditions were associated with rehabilitation therapies.27

Regarding manual therapies, one longitudinal study of persons with low back pain found that older age, female gender, use of pain medication, and reporting depression were related to increased use of acupuncture.24 Other work examining chiropractic care for a range of conditions reported that younger age,28, 29 White race,30, 31 and higher socioeconomic status32, 33 were related to increased use of chiropractic care. In another investigation of OEF/OIF/OND veterans, higher income, uncertain access to healthcare, and presence of multiple pain conditions were related to use of manual therapies.27

Increasing uptake of NPMs for veterans with chronic pain is important as an increasingly acknowledged component of evidenced-based care for chronic pain. A better understanding of who uses NPMs may inform clinicians’ efforts to encourage NPM use. Limitations in existing data regarding correlates of NPM use include published studies more than a decade old, positive shifts in the attitudes towards of NPM treatments in recent years,34 and changes in availability of NPMs. Additionally, few studies focus on veterans.22 The current study examines veterans from the OEF/OIF/OND era, a cohort of veterans that may disproportionately suffer from chronic pain,5 and oversample female veterans, allowing us to examine important sex differences. The aim of this study was to conduct a secondary analysis of baseline survey data from the Women Veterans Cohort Study (WVCS) to examine NPM use, using the three categories identified by VA SOTA, and to explore potential demographic and clinical variables as correlates of NPM use by category.

METHODS

Overview and Participants

Data for the study were derived from the WVCS survey, described in detail elsewhere.35, 36 Eligible participants were military veterans of the OEF/OIF/OND era who enrolled for care in VHA settings between September 12, 2001 and September 30, 2012 (n = 625,082). A subsample of veterans participated in three surveys were administered yearly and recruited primarily via mailings sent to 8465 potential participants from eight states; female veterans were oversampled as a means to equalize numbers of male and female participants. A total of 767 veterans provided consent, and 662 completed the baseline WVCS survey between July 2008 and December 2011, for an overall response rate of 7.7%. This secondary analysis used baseline data from the WVCS survey, and only those who endorsed having pain for 3 months or longer were included, yielding a sample of 460 veterans. The study was approved by the Institutional Review Boards at the VA Connecticut Healthcare System and Yale University School of Medicine.

Measures

Demographics

The demographic section of the baseline WVCS survey included age, sex, race/ethnicity, marital status, employment status, and education.

Use of Non-Pharmacological Modalities (NPMs)

The survey asked of respondents used the following approaches to manage pain in the past year: physical therapy, chiropractic, acupuncture, psychotherapy, massage, educational classes, or exercise. Veterans responded based on all use of NPMs, inside or outside of VHA. Using categories defined by the VA SOTA, we created three variables: use of psychological/behavioral therapies, including psychotherapy or educational classes; use of exercise/movement therapies, including physical therapy or exercise; and use of manual therapies, including chiropractic, acupuncture, or massage.

Pain Intensity

The Brief Pain Inventory (BPI) 37 was used to measure worst, least, average, and current pain intensity in the past week on 0 (no pain) to 10 (worst pain imaginable) scales. Participants also indicated location(s) of their pain by responding to a checklist of possible types (i.e., back pain, neck pain, headache or migraine, stomach ache or abdominal, joint pain, chest pain, facial ache or pain, or whole body pain); finally, participants also indicated the length of time they had experienced pain using categories ranging from 3 to 6 months up to more than 4 years.

Opioid Use

Veterans reporting chronic pain were asked about past-week use of the following opioid analgesics, listed verbatim: morphine (MS Contin, Roxanol, Oramorph), oxycodone (OxyContin, Percocet, Roxicet, Tylox, Endocet), hydrocodone (Vicodin, Lortab, Norco), methadone (Dolophine), fentanyl (Duragesic, Actiq), codeine (Tylenol #3,Tylenol #4), propoxyphene (Darvon, Darvocet), or tramadol (Ultram, Ultracet). Veterans were instructed to report on all medication use, regardless of VHA/non-VHA prescriber status. We created a variable “opioid pain medication use” to indicate whether a veteran used at least one opioid pain medication in the past week.

Non-Opioid Pain Medication Use

Veterans endorsing chronic pain were asked about past-week use of the following non-opioid analgesics, listed verbatim: non-steroidal anti-inflammatory drugs (NSAIDs) (e.g., ibuprofen [Motrin], naproxen [Naprosyn, Aleve], indomethacin [Indocin], meloxicam [Mobic], etodolac, or Celebrex), acetaminophen (Tylenol), herbal or nutritional supplements, tricyclics (e.g., amitriptyline [Elavil], nortriptyline [Pamelor], doxepin, imipramine), muscle relaxants (e.g., cyclobenzaprine [Flexeril], methocarbamol [Robaxin], carisoprodol [Soma]), anti-epileptics (e.g., gabapentin [Neurontin], Lyrica, Topamax), and SNRIs (e.g., Cymbalta, venlafaxine [Effexor]). We did not ask about topical analgesics. Veterans were instructed to respond based on all medication use, regardless of VHA/non-VHA prescriber status. We created a variable “any non-opioid pain medication use” to indicate whether a veteran used at least one non-opioid pain medication in the past week.

Mental Health Symptoms

The survey included the Patient Health Questionnaire-9 (PHQ-9),38, 39 a self-report measure of depressive symptoms, and the PTSD Symptom Checklist-Military version (PCL-M),40, 41 a self-report measure of PTSD symptoms. In this sample, these two measures were highly correlated (r = 0.79). Therefore, we elected to use a symptom composite to avoid concerns of multicollinearity. PHQ-9 scores and PCL-M scores were converted into z scores (M = 0, SD = 1) and averaged to create a mental health composite score representing overall mental health symptom severity.

Data Analysis

Descriptive statistics for the entire sample were calculated for all variables. Less than 1% of data were missing. We examined bivariate relationships between frequency of use of NPMs and demographic/clinical variables (e.g., age, race/ethnicity, sex, education, pain severity, mental health symptom severity, opioid and non-opioid pain medication use) using independent sample t tests, correlations, and chi square tests as appropriate. We used logistic regression to examine demographic and clinical factors associated with the use of each category of NPMs.

RESULTS

Descriptive Analysis (Table 1)

Veterans with chronic pain in the sample (N = 460) were on average 33.76 years old (SD = 10.72), approximately half were female (56.3%), and the majority were White (80.2%). Veterans reported an average pain intensity of 3.45/10 (SD = 1.95). Most veterans reported pain lasting more than a year, with 42.1% reporting pain lasting 1 to 4 years and 40.9% reporting pain lasting 4 years or longer. The most common types of pain were joint pain (80.6%), back pain (80.4%), and headache (64.0%).

Table 1 Descriptive Data (N = 460)
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About one fifth (20.7%) reported past-week opioid analgesic use whereas a large majority reported past-week non-opioid analgesic use (72.4%) with the most common medication class being NSAIDs (62.0%).

A majority (75.9%) reported using at least one NPM in the past year, with 22.6% using a psychological/behavioral therapy, 50.9% using an exercise/movement therapy, and 51.7% using a manual therapy. Veterans used on average 1.68 NPMs (SD = 1.51). The most frequently endorsed NPM was massage, reported by 42.6% of the sample, followed by physical therapy (37.0%). Acupuncture and educational classes (both 8.3%) were the least frequently endorsed. Psychological/behavioral therapy use and exercise/movement therapy use were positively related (X2 = 9.88; p = 0.002), while psychological/behavioral therapy use and manual therapy use were not related (X2 = 0.51; p = 0.48). Exercise/movement therapy use and manual therapy use were positive related (X2 = 25.26; p ≤ 0.001).

Bivariate Analysis (Table 2)

Veterans using psychological/behavioral strategies to manage pain were less likely to be White and more likely to have a college degree. They also reported greater pain severity, worse mental health symptoms, and more pain medication use (opioid and non-opioid). Veterans using exercise/movement therapies were more likely to be female, reported greater pain severity, and reported greater use of opioid and non-opioid pain medications. Veterans using manual therapies were more likely to have a college degree and were more likely to report using non-opioid pain medication.

Table 2 Relationships Between NPM Use and Demographic/Clinical Variables
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Regression Analysis (Table 3)

Psychology/Behavioral Therapies

The odds of reporting the use of psychological/behavioral therapies in the past year was 2.51 (95% CI = 1.46, 4.30, p = 0.001) times greater for veterans with at least a college degree, compared to those without a college degree. Additionally, reporting worse mental health symptoms was related to increased use of psychological/behavioral therapies for pain management, such that for every one point increase on the mental health symptom score composite, the odds of reporting the use of psychological/behavioral therapies for pain management increased by 2.88 (95% CI = 2.11, 3.93, p < 0.001).

Table 3 Logistic Regressions
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Exercise/Movement Therapies

Males were less likely to report using exercise/movement therapies than females (OR = 0.63; 95% CI = 0.43, 0.93, p = 0.02). The odds of reporting use of exercise/movement therapies was 1.82 (95% CI = 1.16, 2.84, p = 0.009) times greater for veterans using non-opioid pain medication vs. those not using non-opioid pain medication. Additionally, for every one point increase in pain severity, the odds of reporting use of exercise/movement therapies was 1.13 (95% CI = 1.00, 1.28, p = 0.04) times greater.

Manual Therapies

White veterans were less likely to use manual therapies than non-White veterans (OR = 0.57; 95% CI = 0.35, 0.94, p = 0.03). The odds of reporting use of manual therapies was 2.11 (95% CI = 1.42, 3.15, p < 0.001) times greater among veterans with a college degree (vs. no college degree), while the odds of using manual therapies was 1.71 (95% CI = 1.09, 2.68, p = 0.02) times greater among veterans taking non-opioid pain as compared to veterans not taking any non-opioid pain medications.

DISCUSSION

In this cross-sectional survey of veterans from the OEF/OIF/OND era enrolled in VHA care, we found that past-year NPM use was reported by a large majority (75.9%) of the sample. One in five veterans reported past-week opioid use, and the majority (72.4%) used a non-opioid medication in the past week. We identified demographic and clinical characteristics related to use of NPMs that deserve comment. These may indicate differences in veteran treatment preferences, provider referral patterns, or availability of NPMs. It is perhaps unsurprising that veterans with worse mental health symptoms were more likely to use psychological/behavioral therapies for pain. Veterans with worse mental health symptoms may be more likely to be connected with mental health providers or to have received psychotherapy in the past. Past experience with therapy may lead providers to be more likely to refer these veterans for pain-focused psychological therapies or may make veterans more likely to accept these referrals.

Consistent with a study using VHA administrative data reporting that female veterans were more likely to receive rehabilitation therapies,22 we found that female veterans were more likely to use exercise/movement therapies compared to men. Research has suggested that men with chronic pain have higher rates of kinesiophobia (fear of movement) than women with chronic pain.42 Perhaps lower rates of kinesiophobia contribute to increased willingness to engage in exercise/movement therapies. Additionally, one study of healthy participants found that vigorous physical activity produced analgesia in women but not men,43 suggesting women may benefit more from exercise therapies than men.

Consistent with previous studies,24,32,33 we found that higher educational attainment and use of non-opioid pain medications were related to increased use of manual therapies. We also found that non-White veterans were more likely to report using manual therapies than White veterans, which was surprising given prior research demonstrating the opposite.30,31 Methodological and study population differences may account for these findings; for example, one study conducted with older adults in Mississippi did not control for socioeconomic status in the analyses30; additionally, none of the studies reviewed was conducted in a veteran population. In the current sample, all participants were enrolled in VHA healthcare, increasing their potential access to manual therapies for chronic pain, which may reduce known racial disparities in accessing healthcare. However, given that veterans’ self-reported treatments received inside and outside of VHA, perhaps higher educational attainment suggests improved access to services, either via higher income levels or improved insurance coverage, which may lead to improved access to manual therapies. Indeed, a study using a related subsample of WVCS survey, respondents found that greater income and uncertain access to healthcare were associated with receipt of the manual therapies described in the current study.27

This study was limited by its cross-sectional design and reliance on self-report data, collected between 2008 and 2011. The data are somewhat old; however, more recent studies of the OEF/OIF/OND population have reported similar characteristics.2 The survey only inquired about a specific set of NPMs, and did not include questions about frequency or dose of medication or NPM treatment. Moreover, although questions were worded to inquire specifically about treatments used for pain, it is possible that some participants endorsed NPM use when that NPM was not pain-focused (e.g., attended psychotherapy that was not pain-focused), and it is not possible to examine details regarding NPMs (e.g., if therapy provided was an evidence-based intervention). Additionally, although only veterans with chronic pain were included in the sample, inquiring about past-week medication use may have captured medications used for acute pain. Furthermore, there was a high nonresponse rate to the survey, and the nonresponse rate was greater for males than females. Analysis of responders versus non-responders from a majority subsample indicated few group differences.35 Although responders were more likely to be White (82.9 vs. 73.4%) and older (32.7 vs. 29.1 years) than non-responders, the groups did not differ on any other demographic measures. Finally, by focusing on OEF/OIF/OND veterans, who often present with chronic pain,2 our sample included veterans who are younger, more likely to be women, and more likely to be ethnic/racial minorities than older cohorts of veterans. This may limit generalizability to older cohorts of veterans and civilian samples.

Despite limitations, this study’s strengths include a moderate-sized sample and an adequate sample of female veterans. The detailed information about self-reported types of medications and NPMs is a strength, as it provided more detail regarding pain management than studies relying solely on EHR data. By using self-reported data, we were able to capture VHA services not easily captured in administrative data.

In summary, results from cross-sectional survey data indicated that the majority of veterans with chronic pain reported using at least one NPM in the past year. Some differences were observed in the use of NPMs based on demographic and clinical characteristics, which may indicate differences in veteran treatment preferences or provider referral patterns. Our findings may be useful in developing targeted interventions to improve referral processes and treatment uptake. For example, veterans with a mental health history may be more amenable to referrals to psychological/behavioral treatment, and providers should be sure to recommend exercise/movement therapies for women veterans. Most importantly, however, providers should emphasize the overall benefits of using NPMs and use a shared decision making approach to determine which NPMs might work best for each patient. Future research should utilize both self-report and EHR data to examine pain management strategy use (including pharmacological and non-pharmacological strategies) over time. Looking at these relationships over time may provide insight into how the combination of treatments or sequencing of treatments relates to pain intensity and pain-related functioning.