Post-Traumatic Stress Disorder Symptoms Are Associated With Incident Chronic Back Pain

A Longitudinal Twin Study of Older Male Veterans

Pradeep Suri, MD, MS; Edward J. Boyko, MD, MPH; Nicholas L. Smith, PhD; Jeffrey G. Jarvik, MD, MPH; Gail P. Jarvik, MD, PhD; Frances M.K. Williams, PhD; Rhonda Williams, PhD; Jodie Haselkorn, MD, MPH; Jack Goldberg, PhD

Disclosures

Spine. 2019;44(17):1220-1227. 

In This Article

Results

Of 342 individuals contacted at 5-year follow-up, 227 (66%) returned mail surveys for the current study and comprised the longitudinal study sample (Figure 1). The sample included 91 MZ pairs (n = 182) and 45 singletons. Compared with other participants of CSP #569 (n = 7341), those in the current study (n = 227) were more likely to report having received or having ever applied for VA disability compensation (25.9% vs. 33.3%; P = 0.01), but were otherwise comparable with respect to all variables examined in this study (data not shown).

The average age of the sample was 62 years, 26% of participants were college graduates, and 52% had an annual household income greater than the US median in 2011 ($50,000) (Table 1).[43] Those with baseline PTSD symptoms (PCL ≥30) were significantly more likely than those without to report having ever used VA health care services, to have ever received or applied for a VA service-connected disability, and to have depression symptoms (PHQ score ≥5) at baseline (Table 1).

At 5-year follow-up, 110 participants (50%) reported incident CBP, the primary study outcome (Table 2, Figure 2). Of the 91 MZ pairs in the longitudinal study sample, there were 86 MZ pairs where both cotwins reported on the presence or absence of incident CBP at follow-up. Among these 86 MZ pairs, the 5-year incidence was 41% in those without baseline PTSD symptoms, and 64% in those with baseline PTSD symptoms. Mean back pain intensity in those with CBP was approximately 5 points on a 0 to 10 NRS scale, reflecting moderate levels of pain intensity, and mean back-related functional limitations were 24 points on a 0 to 100 Oswestry scale. The incidences of chronic low back pain and chronic mid/upper back pain were 45% and 15%, respectively (Table 2, Figure 2).

Figure 2.

Incidence of chronic back pain at 5-year follow-up.

In bivariable within-pair analyses (accounting for familial factors), baseline PTSD symptoms were significantly associated with incident CBP at 5-year follow-up (RR 1.6, 95% CI 1.2–2.1; P = 0.001) (Table 3). The only covariate that met criteria for confounding using the ≥10% change-in-estimate method was VA service-connected disability (data not shown). Within-pair multivariable analyses adjusting for VA service-connected disability yielded nearly the same estimate of association as the bivariable analyses (RR 1.5, 95% CI 1.2–2.1; P = 0.002) (Table 3). Significant associations were also seen between baseline PTSD symptoms and the secondary back pain outcomes (Table 3), although the magnitude of association with incident chronic mid/upper back pain (multivariate-adjusted RR 2.7, 95% CI 1.1–6.3; P = 0.02) was larger than that with incident chronic low back pain (multivariate-adjusted RR 1.6, 95% CI 1.2–2.1; P = 0.001).

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